238.1 Aerial Mapping and LiDAR Surveys: Difference between revisions

From Engineering_Policy_Guide
Jump to navigation Jump to search
← Older edit
Smithk (talk | contribs)
Modot, modot
20,986 edits
m "ensure" correction
m →‎238.1.3 Standard Deliverables for LiDAR Data: changed GeoPak to OpenRoads Designer
 
(16 intermediate revisions by one other user not shown)
Line 2: Line 2:
|-
|-
|'''Figures'''
|'''Figures'''
|-
|[[Media:238.1 Photogrammetric Targets.pdf|Photogrammetric Targets]]
|-
|-
|[[Media:238.1 Aerial Target Notes.pdf|Aerial Target Notes]]
|[[Media:238.1 Aerial Target Notes.pdf|Aerial Target Notes]]
Line 19: Line 17:
|[[Media:238.1 Requisition for Prints of Previous Photography (D-102).doc| Form D-102]]
|[[Media:238.1 Requisition for Prints of Previous Photography (D-102).doc| Form D-102]]
|-
|-
|[http://www.modot.mo.gov/business/standards_and_specs/documents/MoDOT_2006_Survey_Code_Sheet.pdf Survey Coding Sheet]
|[https://epg.modot.org/forms/DE%202017%20Forms/CADD/238.1_Survey_Code_Sheet_2014.pdf Survey Coding Sheet]
|-
|[https://epg.modot.org/forms/DE%202017%20Forms/CADD/238.1.3.pdf Fig. 238.1.3, Aerial Photography and Control Survey]
|}
|}




Photogrammetric surveys achieve the same results as conventional surveys by methods, which require a minimum of fieldwork. Photogrammetric surveys are performed by making measurements from aerial photographs properly oriented to a few field measurements to form, in proper equipment, a small scale three-dimensional model of a part of the earth's surface.  Through the use of stereoplotters the location and elevation of man-made features are obtained from the model. Conventional surveys require numerous field measurements to obtain the same data and information. To ensure proper accounting for each of the various surveying tasks involved with photogrammetric surveys, the [http://www.modot.mo.gov/business/standards_and_specs/documents/MoDOT_2006_Survey_Code_Sheet.pdf correct coding] must always be used.
Aerial Mapping and LiDAR surveys can achieve the same results as conventional topographical surveys by methods which require a minimum of fieldwork. Airborne LiDAR sensors are used by companies in the remote sensing field. It can be used to create DTM (Digital Terrain Models) and DEM (Digital Elevation Models). This is a common practice for larger areas since a plane can take in a swath 1 km wide in one flyover. Greater vertical accuracy can be achieved with a lower flyover and a narrower swath, even over a forest, where the height of the canopy as well as the ground elevation can be determined. Conventional surveys require numerous field measurements to obtain the same data and information.
 
==238.1.1 Surveys Adaptable to Photogrammetry==
 
Projects with certain physical characteristics are adaptable to economical photogrammetric surveys. The districts must make the judgment, based on their knowledge of the requirements of each project, whether a conventional or photogrammetric survey best satisfies their need. Factors that influence this decision include:


* '''Scope of the project:''' The use of photogrammetric methods, in almost all cases, will result in the most economical survey for projects encompassing large areas. Conversely, smaller projects are best suited for field surveys. It is difficult to provide a quantitative guideline to determine which projects fall into which category. Generally, projects less than 1300 ft. long are best when field surveyed. Photogrammetric projects under 8200 ft. long can have straight line targets and any project longer than 8200 ft. will use the triangulation method of targeting.
==238.1.1 Surveys Adaptable to Aerial Mapping and LiDAR==


* '''Type of project:''' Sometimes photogrammetry can be economically applied to resurfacing and widening projects in highly developed areas to obtain planimetry (2D only). These surveys do not require vertical control. Projects that required precise elevations are to be field surveyed.  
Projects with certain physical characteristics are adaptable to aerial mapping and LiDAR surveys. The districts must make the judgment, based on their knowledge of the requirements of each project, whether a conventional or aerial mapping and LiDAR survey best satisfies the need. Factors that influence this decision include:
* '''Scope of the project:''' The use of aerial mapping and LiDAR methods, in almost all cases, will result in the most economical survey for projects encompassing larger areas. Conversely, smaller projects are best suited for field surveys. It is difficult to provide a quantitative guideline to determine which projects fall into which category. Generally, it is better to field survey projects that are shorter than 1300 feet. Aerial mapping and LiDAR projects should be reviewed to determine the best application of LiDAR that will meet the project needs and budget.
[[image:238.1.1.jpg|right|275px|thumb|<center>'''Rough terrain with heavily timbered areas'''</center>]]
* '''Type of project:''' The project's scope will usually be the best guide for the type mapping needed. Urban enhancements of existing structures may lend themselves to a terrestrial or mobile type of collection for the best results. Where a cross country new alignment would be much better suited for aerial platform like a fixed wing aircraft or helicopter.  


* '''Terrain:''' Projects with terrain that is difficult or impossible to field survey, will be surveyed by photogrammetric methods. These include projects in highly developed areas, extremely rough terrain, heavily timbered areas as well as bridge surveys for large streams.  
* '''Terrain:''' Projects with terrain that is difficult or impossible to field survey will be surveyed by aerial mapping and LiDAR methods. These include projects in highly developed areas, extremely rough terrain, heavily timbered areas as well as bridge surveys for large streams.


* '''Time consideration:''' Time sensitive projects will be field surveyed, because of the lead-time necessary for photogrammetric surveys. Table 238.1.1 shows guidelines to determine what type of survey best suites a project.  
* '''Time consideration:''' Time sensitive projects will be field surveyed, because of the lead-time necessary for aerial mapping and LiDAR surveys. Table 238.1.1 shows guidelines to determine what type of survey best suites a project.


===<center>Table 238.1.1</center>===
===<center>Table 238.1.1</center>===
{|border="1" style="text-align:center" align="center" cellpadding="3"
{|border="1" style="text-align:center" align="center" cellpadding="3"
! style="background:#00BFFF " colspan="2"|Photogrammetric Survey Versus Conventional Survey
! style="background:#BEBEBE" colspan="2"|Aerial Mapping and LiDAR Survey Versus Conventional Survey
|-style="background:#00BFFF"
|-
!style="background:#00BFFF"|Photogrammetric||Conventional  
! style="background:#f5f5f5"|Aerial Mapping and LiDAR!! style="background:#f5f5f5"| Conventional  
|-style="background:#cccccc"
|-
|Wide Corridor Projects|| Resurfacing Projects  
|Wide Corridor Projects|| Resurfacing Projects  
|-style="background:#cccccc"
|-
|Relocation Shoulder|| Widening Projects  
|Relocation Shoulder|| Widening Projects  
|-style="background:#cccccc"
|-
|Large Area Planimetric (2D) Surveys||Small Area Planimetric (2D) Surveys  
|Large Area Planimetric Surveys|| Small Area Planimetric Surveys  
|-style="background:#cccccc"
|-
|Large Bridge Replacements||Small Bridge Replacements  
|Large Bridge Replacements|| Small Bridge Replacements  
|-style="background:#cccccc"
|-
|> 1300 ft.||< 1300 ft.  
|> 1300 ft. || < 1300 ft.  
|-style="background:#cccccc"
|-
|Interchanges|| -  
|Interchanges || -  
|-style="background:#cccccc"
|-
|Rough Terrain|| -  
|Rough Terrain || -  
|}
|}  
 
 
In addition, district personnel requesting mapping should discuss project specifics with the aerial mapping and LiDAR personnel when determining which method of survey better suits the project.
 
==238.1.2 Stages of Aerial Mapping and LiDAR Services==
 
Data acquisition for aerial mapping and LiDAR surveys are provided by professional consulting services.  These professional consultant services are managed by [https://modotgov.sharepoint.com/sites/DE/ Design Division].  These services are provided via the “Annual Flight Program Contract” and the following sequential stages must be coordinated between the district and Design Division:
 
:1. Recommendations for the flight program
:2. Mapping limit plan
:3. Accuracy planning
:4. Consultant selection
:5. Quality control on projects
:6. Review and quality checks on aerial mapping and LiDAR survey data
:7. Furnishing electronic data to the district.
 
===238.1.2.1 Recommendations for Flight Program===
 
The district recommends projects for the flight program each year at the request of [https://modotgov.sharepoint.com/sites/DE/ Design] by the last day of September. Projects recommended for mapping are those that a location study, if necessary, has been approved, or projects for which this will be completed in time to obtain the data during the flying season (approximately December 15 to April 15). Normally, projects that are in the design year of the approved STIP are considered, but other projects may be considered if conditions warrant.
 
===238.1.2.2 Flight Planning===
 
[http://sp/sites/de/Pages/default.aspx Design] performs flight planning, but information from the district is necessary to efficiently plan the the aerial mapping and LiDAR mission. The district furnishes information including the location of the proposed improvement indicated in a CADD drawing file, and the desired accuracy.  Mapping and photography limits are to be submitted electronically using CADD software and ProjectWise.
 
It is desirable to limit the aerial mapping and LiDAR corridor to only that area that is necessary for the design of the project.  The district's recommendation regarding the type and extent of aerial mapping and LiDAR survey data coverage will consider the following:
 
:* For planimetric coverage, corridors will include all features that may affect design considerations and right of way takings. Planimetric corridors do not have to be connected but must be within the area in which horizontal controls have been established.
 
:* For terrain coverage, corridors will be limited to the area necessary for earthwork computations. Generally, this area is within the limits of proposed right of way. Terrain corridors do not have to be connected but must be within the area in which horizontal and vertical control have been established.
 
:* Generally, corridor requests do not include areas for drainage computations. Keep in mind that aerial mapping and LiDAR data should be supplemented with conventional survey data and shall be verified by the district survey party .
 
===238.1.2.3 Accuracy Planning===
 
To best extract topographic and manmade features from the LiDAR data, three density and accuracy levels are used, as describe below: 
 
:'''Type A, Roadway and Pavement Scans (Mobile, Helicopter Based or Terrestrial LiDAR)'''
 
::1) Internal Horizontal / Vertical Accuracy of 0.3 ft. at 95% confidence.
 
::2) Maximum point spacing of 0.3 ft. on the full classified LAS file.
 
:'''Type B, Corridor and earthwork Scans Urban (fixed wing or Helicopter Based Aerial LiDAR)'''
 
::1) Internal Horizontal / Vertical Accuracy of 0.5 ft. at 95% confidence.
 
::2) Maximum point spacing of 1 ft. on the full classified LAS file.
 
:'''Type C, Corridor and earthwork Scans Rural (fixed wing)'''
 
::1) Internal Horizontal / Vertical Accuracy of 0.5 ft. at 95% confidence.
 
::2) Maximum point spacing of 2 ft. on the full classified LAS file.
 
===238.1.2.4 Consultant Selection===
 
Refer to [[:Category:134 Engineering Professional Services|EPG 134 Engineering Professional Services]].
 
===238.1.2.5 Quality Control on Projects===


Quality control all projects will be done by the [https://modotgov.sharepoint.com/sites/DE/ Central Office Design survey staff] to ensure the data provided meets MoDOT’s needs for engineering mapping and design.


In addition, district personnel that request mapping, will discuss project specifics with the photogrammetry personnel when determining which method of survey best suits the project.  
To verify the accuracy of the surface of the delivered aerial mapping and LiDAR, the Central Office survey staff will take check shots along the main alignment of the project at least every 200 ft. and alternate shoot every 400 ft. each side of the main alignment.  


==238.1.2 Stages of Photogrammetric Services==
To verify the accuracy of extracted features of the delivered aerial mapping and LiDAR, the Central Office survey staff shall take check shots along curb lines, bridge rails, retaining walls and other features with elevation differences that can easily be identified.  


Photography and compilation for photogrammetric surveys are centralized in [http://wwwi/design/default.htm Design] since these require the use of expensive equipment that is only economical if fully utilized. All other work is performed in the district. The following sequential stages for a photogrammetric survey must be coordinated between the district and photogrammetric personnel:
===238.1.2.6 Review and Quality Checks on Aerial Mapping and LiDAR Survey Data===


1. Recommendations for flying program
All quality control will be done using MoDOT's CADD software. Project control shots will be compared to the surface model and topographic and manmade features provided by the aerial mapping and LiDAR consultant and must meet the internal horizontal/vertical accuracy defined by the scope of services at 95% confidence.  


2. Mapping and Photography limit plan
A report will be run and kept with the files for the project certifying these accuracies.


3. Flight planning
Any acceptance of data below these standards will have written documentation explaining the prescence of this data and what resulting developments may be encountered during the design process.  


4. Target planning
===238.1.2.7 Furnishing Electronic Data to the District===


5. Targeting
All data will be delivered to the districts via ProjectWise. Once all the data has been delivered and has met the quality standards, Central Office will place the file into the districts' ProjectWise folders for access.


6. Photography
==238.1.3 Standard Deliverables for LiDAR Data==


7. Establishing control
The consultant shall provide to the Commission the following items:


8. Compiling photogrammetric survey data
:'''1) Three ASCII coordinate files''' all containing the primary control, photo control and check points for the project survey. These files are:


9. Furnishing electronic data to the district.  
::<u>Primary Control File.</u> A file listing control positions by point number, X, Y, and Z values in project units referenced to the Missouri Coordinate System of 1983, the correct zone name (ex. East Zone), with X and Y values modified by the projection factor. This ASCII formatted file will be in the form of: J######.rec.


The district performs Stages 1 and 2 on all projects, and in some cases may perform Stages 5 and 7.
::<u>The Geodetic Control File.</u> A file containing latitude and longitude information for all control points named J######.txt with file format listed on page 3 of [https://epg.modot.org/forms/DE%202017%20Forms/CADD/238.1.3.pdf Fig. 238.1.3, Aerial Photography and Control Survey]. All OPUS solution sheets and/or data sheets from post processed static GPS sessions, calculations for grid and projection factor including the centroid point, mean elevation and the final grid and projection factor will also be listed in this file.


==238.1.3 Recommendations for Flying Program==
::<u>Check Shots File.</u>  A file listing quality control positions by point number, X, Y, and Z values in project units referenced to the Missouri Coordinate System of 1983, the correct zone name (ex. East Zone), with X and Y values modified by the projection factor. This ASCII formatted file will be in the form of: J######.txt.


The district recommends projects for the flying program each year at the request of [http://wwwi/design/default.htm Design] by the last day of September. Projects recommended for mapping are those that a location study, if necessary, has been approved, or projects that this will be completed in time to obtain the photography during the flying season (approximately December 15 to April 15). Normally, projects are in the design year of the approved STIP are considered, but other projects may be considered if conditions warrant. Other projects, flown only for aerial photo coverage in preparation for a location study, will also be considered at this time.  
:'''2) MoDOT Survey Report.''' A MoDOT survey project report for each project. It shall include copies of all inter-visible control survey pair station descriptions along with all benchmark descriptions and field ties. A sketch of each point shall be provided showing the relative location of field ties to the point being referenced. The consultant shall provide a letter certifying that the below mentioned surveying specifications have been achieved for this project. The letter shall document the relative positional accuracies in parts per million, the confidence level in percent and the post adjustment residual values in centimeters that were achieved on this project. If any portion of the survey does not comply with these specifications, a written report substantiating the material variances from the specifications with the responsible surveyor’s signature is required. The Commission reserves the right to disallow variations.


==238.1.4 Flight Planning==
:The survey report documents proof of these specifications:


[http://wwwi/design/default.htm Design] performs flight planning, but information from the district is necessary to efficiently plan the photographic mission. The district furnishes information including the location of the proposed improvement indicated in a [http://caddnet/index.php?title=MicroStation MicroStation] Design file, and the desired mapping scale.  Mapping and Photography limits are to be submitted electronically using MicroStation and [http://caddnet/index.php?title=ProjectWise ProjectWise].
::a. Fixed preprocess baseline solutions.


It is desirable to limit the photogrammetric corridor to only that area which is necessary for the design of the project. Separate corridors, planimetric (2D) and terrain (3D) can be described for photogrammetric surveys. The district's recommendation regarding the type and extent of photogrammetric survey data coverage will consider the following:
::b. Control station relative positional accuracies of 10 ppm in relation to adjacent stations at the 95% confidence level.  


* For planimetric (2D) coverage, corridors will include all features that may affect design considerations and right of way takings. Planimetric corridors do not have to be connected but must be within the area in which horizontal controls have been established.  
::c. Post adjustment residual values <3 cm in any dimension for control stations.  


* For terrain (3D) coverage, corridors will be limited to the area necessary for earthwork computations. Generally, this area is within the limits of proposed right of way. Terrain corridors do not have to be connected but must be within the area in which horizontal and vertical control have been established.  
::d. A dgn file with all survey control points plotted and labeled.


* Generally, corridor requests do not include areas for drainage computations. Keep in mind that photogrammetric data should be supplemented with conventional survey data, and shall be verified by the district survey party.
:'''3) An Orthomosaic''' captured simultaneously with LiDAR or separate aerial sensor, meeting the following requirements:


==238.1.5 Theory of Flight Planning==
::a. Shall have a resolution of 0.5 ft. per pixel.


There is a direct relationship between the flight height, photo-coverage, focal length of the camera, and the size of the negative, which is taken into consideration when planning a photographic mission. As the flight height increases, the photo-coverage increases and the scale of the negative becomes smaller.  Where the photogrammetric mapping is to be performed to a predetermined scale, the flight height, and consequently the photo-coverage on any one negative is predetermined by the camera and stereoplotter being used.  On low-level photographic missions or where mapping of relatively large areas is desired, it is sometimes necessary to plan extra flights to obtain coverage of entire areas.  Photographic missions cannot be properly planned without knowledge of the intended use of the photography or the scale desired for the mapping. The focal length of the department's camera is 5.9 in. and the photo is 9 in. square.  Whereas the focal length of the digital mapping camera is 4.7 in. and the photo coverage is 3.6 in. x 6.5 in.
::b. Shall be tiled, with tiles no larger than 3250 x 3250 pixels.


A summary of common flight heights is shown on Tables 238.1.5.1 and 238.1.5.2.  The accuracy of the mapping compiled by photogrammetry personnel is in direct relationship to the flight height. Photography flown at an altitude of 1500 ft. above mean sea level has a mapping accuracy so that 90% of the elevations will be within 6 in. Photography flown at an altitude of 3000 ft. above mean sea level has a mapping accuracy so that 90% of the elevations will be within 12 in.  
::c. Shall encompass the area requested for mapping.


===<center>Table 238.1.5.1</center>===
::d. Shall be a geotiff and accompanied by a projection file (.prj).
{|border="1" style="text-align:center" align="center" cellpadding="3"
! style="background:#00BFFF " colspan="5"|Photogrammetric Relationships (Frame Camera)
|-style="background:#00BFFF"
! Flight Height AMG (ft.)||Photo Cover (ft.)||Photo Scale (ft./in.)||Min. Contour Interval (ft.)||Accuracy (ft.)
|-style="background:#cccccc"
|1500||2264 x 2264||250||1||0.5
|-style="background:#cccccc"
|3000||4528 x 4528||500||2||1
|-style="background:#cccccc"
|6000||9055 x 9055||1000||5||2.5
|-style="background:#cccccc"
|12000||18110 x 18110||2000|| - || -
|}


===<center>Table 238.1.5.2</center>===
::e. Shall include a shape file indicating the locations of the orthomosaic tiles.
{|border="1" style="text-align:center" align="center" cellpadding="3"
! style="background:#00BFFF " colspan="5"|Photogrammetric Relationships (Digital Mapping Camera)
|-style="background:#00BFFF"
! Flight Height AMG (ft.)||Photo Cover (ft.)||Photo Scale (ft./in.)||Min. Contour Interval (ft.)||Accuracy (ft.)
|-style="background:#cccccc"
|1181||907 x 1633||250||1||0.5
|-style="background:#cccccc"
|2363||1841 x 3266||500||2||1
|-style="background:#cccccc"
|4725||3628 x 6532||1000||5||2.5
|-style="background:#cccccc"
|9450||7256 x 13064||2000|| - || -
|}


:'''4) LiDAR''' projects, the following shall be delivered:


==238.1.6 Authority to Target==
::a. Data will be delivered in LAS version 1.2 format or newer with the following information.


[http://wwwi/design/default.htm Design] consults the targeting for the flight program, however the district may perform  their own targeting. If the district decides to perform the targeting, the target locations will be provided by Design in a MicroStation design file and coordinate file. Before targeting the location of the improvement, the district must check with Design to ensure the plane will be available for photography as scheduled.  
:::i. Record return


==238.1.7 Targeting and Photogrammetry==
:::ii. Intensity


If the the targeting is performed by the district, the district will advise [http://wwwi/design/default.htm Design] when targeting is complete targeting is complete so the location can be photographed as soon as possible. The district is furnished one set of contact prints of the aerial photographs. The district will use the contact prints to indicate the target locations and additional vertical control if needed.
:::iii. GPS time


==238.1.8 Vertical Control==
:::iv. Swath line number designation


As soon as practical after completing the photography, the district will be furnished with contact prints to plan for obtaining vertical control, if needed.  The district then proceeds with the survey to obtain vertical control.  When the vertical control survey is completed, the district returns the vertical control photographs along with the vertical control field notebook to the Design Division.
:::v. Classification values after trimming (without data voids between swath lines)


==238.1.9 Vertical Control Elevations==
::::0 = raw, never classified
::::1 = unclassified
::::2 = ground (i.e. bare earth)
::::3 = low vegetation
::::4 = medium vegetation
::::5 = high vegetation
::::6 = building
::::7 = low point
::::9 = water
::::10 = bridge
::::12 = overlap


The district is furnished with photographs showing the required vertical control points. The location of these points is marked with a red circle and a 900 series number on the front of the photographs.  The Design Division places a description of the points on the back of the photographs.  The district is required to provide the described point elevation with the book and page number of the respective survey field book notes.  Examples of these points are targets, centerline of the road at entrances, fence corners, sidewalk intersections, top of manholes and "ground 10 ft. east of lone tree".  The person picking the point on the photograph uses a pocket stereoscope since it is important to select the exact location.  A number on the front of the photograph identifies these points.  Level lines for establishing the elevations are turned through the control point.  A complete set of level notes is kept in a separate notebook.  The point identification number and description for each vertical control point elevation is identified in the notebook.  The elevations of the points, along with the notebook page and number used for recording the elevation are recorded by the field personnel on the back of the photograph in the space provided.  The district adds the names of important streets and roads appearing on the photographs.
::b. LiDAR Processing Report.


==238.1.10 Datum==
::c. Vertical Accuracy Report.


All elevations and vertical control are based on USGS or NGS datum.
::d. A shape file containing numbered LAS tiles.


==238.1.11 Distribution of Aerial Photographs to the District==
:'''5) ASCII coordinate file''' for each project, containing the following items for each point:


Digital images will be furnished to the district for retention in addition to the contact prints provided for vertical control and corridor delineation. An OrthoMosaic will be furnished to the district also.  
::a. X, Y, and Z coordinates using the Missouri Coordinate System of 1983, the correct zone name (ex. East Zone), modified by a factor developed by the consultant.


==238.1.12 Identification of Aerial Photographs==
::b. Feature code using MoDOT Standard Surveying Feature Codes.


A series of numbers appear along the leading edge of all aerial photographs for identification.  A photograph labeled as "96 67 1:6000 FEB 2, 1986 265 1 109" is a photograph in St. Louis County (96), on Route 67, flown at a photo scale of 1:6000, on the specified date, located on roll 265, flight 1, exposure 109 (prior to 1987, the label format was county, route, roll, flight, exposure, scale and date).  The flight number and exposure number is the portion of the photograph identification number used by survey parties as a reference in their field books.  A duplicate print of any aerial photo may be ordered by specifying the roll number and the exposure number.  In addition to these numbers, each photograph contains other marginal information such as number of camera exposures, time of exposure, and altimeter reading, that are for the use and reference of the photogrammetry section.
:'''6) Microstation and OpenRoads Designer files''' to be provided:


==238.1.13 Horizontal Control==
::a. Provide a '''Topo_ConsultantName_JOB#.dgn''' ('''3D''' MicroStation file) of all the topographic and manmade survey data collected.


Horizontal control for photogrammetric surveys is defined as the field control required to orient the photographs to a datum line that may be either the survey centerline or a random traverse line.  The preferred method is to establish a random base or traverse line that is tied to photo-identifiable objects or random targets and from which the final survey centerline is computed.  Another method is the establishment of the survey centerline in the field with targets placed on the centerline prior to photography so the targets are visible and identifiable on the photographs, thereby delineating the location on the photographs. Another method is the establishment of the survey centerline after the photography and tying the centerline to photo-identifiable objects or random targets. The preferred method is used where it is impractical to survey the centerline because of obstructions such as extensively developed areas or where the best location is not apparent until after the mapping is complete. The second method is used when the location is definite and the project completion schedules will allow the centerline to be established prior to the photography.  The third method is used on short projects when there is not sufficient time in the project completion schedule to establish targets prior to photography.
:::i. All dgn files will be based on modified state plane coordinates, using the projection factor for the project as described in [[#238.1.4 Datum and Horizontal Control|EPG 238.1.4 Datum and Horizontal Control]].


==238.1.14 Post-Flight Horizontal Control==
:::ii. Working units: U.S. Survey Foot


Targets are planned to minimize Post-Flight Control, but in some cases where a target may have been destroyed or disturbed, [http://wwwi/design/default.htm Design] will request Post-Flight Control. This requires photo-identifiable objects be tied to a traverse line. Horizontal control points are indicated by a red triangle with an 800 series number on the front of photographs furnished to the district for horizontal control.  A description of the points is included on the back of the photograph.  Both horizontal and vertical control points may be indicated on the same photograph. Examples of these points are the center of manholes, sidewalk intersections, pavement joint or intersections, power poles or other photo-identifiable objects.  The survey party establishes the position of these points in the field, references them to the centerline or to the base traverse. The position includes an accurate angle and horizontal distance to the base traverse or the state plane coordinates of the point. The horizontal control is planned before the centerline or traverse line is established in the field and the survey party leaves recoverable horizontal control points near the probable centerline of the roadway.
:::iii. Features shall be plotted according to MoDOT CADD Standards. Features to be plotted at 1” = 100’ scale. Standards are available for Openroads Designer located in CADD's [https://www.modot.org/cadd-environment ORD Workspace].  


==238.1.15 Accuracy==
::::''Topography Features.''  The mapping data shall include natural positions on the earth’s surface within the project limits that determine the configuration of the terrain.  The positions will be in the form of points and strings that locate vertical and horizontal transitions.


At least second order survey accuracy is necessary.  The acceptable accuracy tolerances for second order surveys are shown in Table 238.1.15.  The accuracy of any traverse is not known until it is closed. The traverse may be closed on itself by looping or by tying the ends of the traverse to points on another traverse or triangulation network of as high or higher order.  A second order traverse may be tied to a first or second order network, but not to a third order network.  Most high order monuments were established by the NGS or the USGS.  However, some cities have monuments established by first or second order surveys.  Descriptions, state grid coordinates, geodetic locations and grid and geodetic azimuth are obtained for these monuments by contacting the proper governmental agency.
::::''Planimetry Features.'' The mapping data shall include the positions of all natural and all man-made features within the project limits. The positions will be in the form of points and strings that define the shape, size and position of the features.


===<center>Table 238.1.15, Tolerances</center>===
::b. Terrain and Geometry information files will be based on modified state plane coordinates, using the projection factor for the project as described in [[#238.1.4 Datum and Horizontal Control|EPG 238.1.4 Datum and Horizontal Control]].
{| border="1" class="wikitable" style="margin: 1em auto 1em auto"
|+
! style="background:#BEBEBE" colspan="2"|Second-Order Class II Survey Accuracy
|-
|align="center"|'''Measurement'''||align="center"|'''Tolerance'''
|-
|align="center"|Distance||align="center"|1:20,000
|-
|align="center"|Angular||align="center"|<math>10 sec.\times \sqrt{n}</math>
|}


<center>n = number of P.I.s in the traverse</center>
::c. OpenRoads Designer Terrain Models for the entire project. Terrain models should not exceed 200 megabytes.


==238.1.16 Targeting==
==238.1.4 Datum and Horizontal Control==
[[image:238.1.16.jpg|right|thumb|<center>'''Training on a GPS system'''</center>|235px]]
Targets may be placed any time after the location of the proposed improvement is established.  When targets are placed before the centerline is staked, the targeted points are established and referenced so the target locations can be accurately re-established and their station location determined when the centerline is staked.  Targets are the preferred method of making photo identifiable points to which horizontal and vertical datum can be referenced to control the mapping project.  The targeted points are to be established with care to ensure they are in useful locations with clear fields of view on the ground to aid future reference to centerline survey control.  Targets are located on level ground with the sky unobstructed 10 degrees above the horizon so satellites are visible to the global positioning system (GPS) receivers.  It is preferred to locate targets out of traffic as the GPS receivers may have to occupy the target for 90 minutes at a time.  The surveyor may begin collection of horizontal and vertical control data before the area is photographed.  Aerotriangulation is a process to supplement the horizontal and vertical control normally required to control aerial photographs.  Measurements of angles and distances on overlapping photographs are related into a spatial solution using the perspective principal of the photographs.  Methods of aerotriangulation allow the photogrammetrist to supplement the field control data by an interpretative process to reduce the amount of field control required to properly orient the photo models.  Those mapping projects that are of greater length than four photographs can have the field control requirements reduced significantly by the use of aerotriangulation.  Projects which are several miles in length can have the field control reduced to one third of that required by a fully controlled job with the use of aerotriangulation.  Therefore, with limited field control it becomes even more critical to accurately locate and identify the targeted control points.


===238.1.16.1 Material for Targets===
===238.1.4.1 Linear measures===


White paint or reflective white marking tape is used for targets on paved surfaces.  Unbleached muslin is used for targets on grass, dirt or aggregate surfaces. Paint is available in the district while marking tape and muslin is stocked in the central warehouse for requisition by the district.
Linear measures will be made in the English System. The base unit will be the United States Survey Foot (and decimal parts thereof).


===238.1.16.2 Spacing and Placement of Targets===
===238.1.4.2 Coordinate System===


Rough target locations will be provided by [http://wwwi/design/default.htm Design] in both MicroStation design and xy coordinate fiels.  Targets are to be spaced in accordance with specific [[Media:238.1 Photogrammetric Targets.pdf|guidelines]].  The distances are a function of the flight height and the desired contour interval.  All of the distances for target spacing may be adjusted by ten percent to allow proper placement in the field.  The mapping project must begin and end with three horizontal and vertical control targets that are roughly placed in a triangular pattern.  The two lateral targets are spaced at the offset distance with the third target placed near the mapping corridor.  No mapping will be done beyond the last target; therefore, enough targets must be placed to ensure adequate coverage.  Position targets in locations with a good field of view to minimize the cutting of vegetation and reduce the number of required ground setups.  Targets are located as required for visibility from the air in areas free of shadows.  When targets are placed on paved shoulders of the roadway, it is suggested the northern shoulder be used to avoid obscuring the target with shadows from objects on the southern side of the road.  Painted targets on pavement, located within public right of way, are preferred to cloth targets located on private property.  When cloth targets are placed, they must be located on level areas with all underbrush and weeds removed adjacent to the targets.  Targets are located where they are least likely to be disturbed.  Targets are placed so the time lapse between placing the targets and the photography is held to a minimum.  If the time lapse is of such duration that it may cause doubt as to the target condition, the targets are checked immediately prior to photography.  
All coordinates shall be based on the State Plane Coordinate System, North American Datum (NAD) of 1983 (1997) in the appropriate zone for the project.  


===238.1.16.3 Field Notebooks (Targets)===
===238.1.4.3 Vertical Datum===


A separate notebook is used to record the target locations and descriptions. The notes include, for each target, the target numbers, shape of the target, and the target ties. A sketch should be provided in the field notes so someone who is not familiar with the location can identify each target on the photographs and easily relocate the targets in the field. Offset distances are recorded for targets that are offset. The targets are listed in numerical sequence in the field book. [[Media:238.1 Aerial Target Notes.pdf|Acceptable examples]] for recording target notes are available.
The elevations shall be based on the North American Vertical Datum (NAVD) of 1988. The elevations shall be based upon ellipsoidal heights that have been modified by the most current NGS Geoid model.


==238.1.17 Base Traverse Surveys==
===238.1.4.4 Projection Factor===


A high order accuracy base traverse is established after photography for use as horizontal control and for use in computing the centerline location.  This traverse is established with electronic distance measuring equipment and a theodolite, a total station or a GPS unit.
The consultant is responsible for developing a project projection factor based on the ''Missouri Coordinate System of 1983 Manual for Land Surveyors''.  


==238.1.18 Traverse Adjustment==
'''Scale Factor.''' Using the most easterly and westerly control points within the project to develop a centroid point for a project. Use the converted English easting of the centroid point in the correct zone formula, below.  


Actual trial field surveys have been conducted to determine the most efficient methods for second order accuracy surveys. A computer program has been written based on these methods for the adjustment of traverses that practically eliminates the need for manual calculations.  Use of this computer program requires the following methods and procedures be used:
:<math>East\, Zone = \frac {(easting\,-\,820,208.3333)}{393,700}\, * \,0.00000000045\, * \,(easting\,-\,820,208.3333)\, +\, 0.9999333 </math>


* '''Establishing traverse stations'''. After the general location of the base traverse is established, the traverse stations are selected.  Traffic, parked cars, and the location of objects, which might cause refraction, are considered. Once the location of the stations is determined, monuments are erected and referenced.  The monument is of a material not subject to easy deterioration or movement, like a cross in concrete or 100d spike driven below the ground line.  The traverse stations are located in areas with easy access having good fields of view that will not be disturbed by normal activities until the centerline can be staked.
:<math>Central\, Zone = \frac {(easting\,-\, 1,640,416.6665)}{393,700}\, *\, 0.00000000045\, *\, (easting\,-\, 1,640,416.6665)\, +\, 0.9999333 </math>


* '''Turning angles'''. If practical, angles are turned at the time of day best suited for this type of work.  Early morning offers the advantage of lack of heat waves and little refraction.  When angles are being turned under a hot sun the instrument must be shaded.  In urban areas traffic volume may dictate the best time of day for turning angles.  Range poles are used on long sights while plumb bobs are used on short sights.  A tripod is used to hold them over the station.  The range pole is plumbed using a tribach with optical plummet.  The instrument is carefully leveled and centered over the station.  [[Media:238.1 Second Order Traverse Notes.pdf|Traverse angles]] are turned eight times, four direct and four reversed, using the mean angle.  Four angles are turned to sub-points, two direct and two reversed, with the mean value used. Angles to mapping targets are turned twice, once direct and once reversed, again with the mean angle used.  When a theodolite is used, vertical angles are also measured to convert the slope distance measured by the electronic distance measuring equipment to horizontal distance.
:<math>West\, Zone = \frac{(easting\,-\, 2,788,708.3331)}{393,700}\, *\,0.00000000045\, *\, (easting\,-\, 2,788,708.3331) \,+\, 0.9999412 </math>


* '''Measuring distance'''.  Distances are measured with an electronic distance measuring instrument (EDM) or a total station.  Distances are measured to reflectors that are placed on a tripod and centered over the survey point.  Each distance to a traverse station or sub-point is measured four times.  Distances to a mapping target are measured twice.  In each case the mean of the measured distance is used.  In the case of an EDM, which is a slope distance, the measurement must be converted to a horizontal distance.


* '''Field notebooks (traverse)'''.  [[Media:238.1 Target Location Notes.pdf|Acceptable examples]] for traverse notes are available.
'''Elevation Factor''' is determined by dividing the ellipsoid radius by the ellipsoid radius plus the mean elevation for the project.  


* '''Polaris and Sun observations'''. To properly close some traverses it is necessary to obtain the correct bearing or azimuth of some of the lines involved by Polaris observation. Computations for second order observations of Polaris at any hour are found in any ephemeris. There are two important considerations in the field procedure of a Polaris observation:
:<math>Elevation\, Factor = \frac{20,909,689.00}{\Big(20,909,689.00\, + \,[elevation\, in\, feet\,-\, 100.065]\Big)}</math>


# The theodolite must be level
# The time must be correct


The theodolite must be in adjustment with good workmanship performed by the instrument operator.  The correct time is obtained by radio from the Bureau of Standards, 2.5, 5.0, 10.0, 15.0 and 20.0 megacycles, the Naval Observatory, 113 kilocycles (five minute period every hour), or the Canadian Observatory, 7.5 megacycles.  If a portable short-wave radio is available it is taken to the field.  If not, a watch used is checked before and after the observation.  Field procedures used to give a second order Polaris observation are as follows:
'''Grid Factor''' is the result of multiplying the Elevation Factor by the Scale Factor of the centroid point of the project.  
# The theodolite is set over the traverse station and leveled carefully. With the telescope, direct a back sight on the traverse station at the other end of the line being checked, with the circle reading read and recorded.
# The telescope is turned to the star and the instant that the star passes behind the cross hair is noted.  The time is recorded to the nearest second, along with the circle reading.
# This procedure is repeated four times with the telescope direct, and four times with the telescope reversed.
# Each angle and time is used to compute a bearing of the survey line.  The mean of these eight computed bearings is used.


An [[Media:238.1 Polaris Observation Notes.pdf|acceptable example]] for recording a second order Polaris observation is available.  Sun observations are an additional way to establish bearings.  Using an ephemeris, the correct time, and following procedures for correctly sighting the sun, bearings can be established.  This procedure may not be as accurate as GPS or a Polaris observation, but can be used as another tool by the surveyor.
:Grid Factor = Elevation factor * Scale factor


* Vertical control.  The elevation of three or more vertical control points is necessary on each photograph to orient the photograph vertically in the stereoplotter.  Aerotriangulation permits the photogrammetrist to reduce the amount of required ground control elevations for an entire project but proper ground elevations are still required to obtain reliable surface elevations.


* Benchmarks and centerline profile.  Benchmarks are established prior to obtaining the vertical control.  An elevation is obtained at each target.  The centerline profile is taken from the aerial contours.  After the designer establishes the approximate location of culverts using the aerial contours, culvert sections are taken in the field.
'''Projection Factor''' is the reciprocal of the grid factor.


* Extra elevations.  In running levels from the established benchmarks to the vertical control points, the survey party is encouraged to obtain elevations for additional photo-identifiable points that may be useful.  If a point selected by the photogrammetry section cannot be identified in the field, the elevation of one additional point is obtained on each side of the unidentifiable point in the direction of the line of flight.  The location of the additional points is marked with a cross on the photograph, pin pricked with the elevation and description recorded in the field books and on the back of the photographs.
:Projection Factor = 1 / Grid factor


* Field notebooks (vertical).  [[Media:238.1 Vertical Control Field Notes.pdf|Vertical control field notes]] are recorded.  Field books used in obtaining the vertical control are forwarded to [http://wwwi/design/default.htm Design] with the vertical control photographs and the target elevations as soon as the fieldwork is completed.  All notebooks are returned to the district when the plotting is completed or at any time on request.
==238.1.5 Field Notebooks (Targets)==


==238.1.19 Aerial Photogrammetry==
A separate notebook is used to record the target locations and descriptions. The notes include, for each target, the target numbers, shape of the target and the target ties. A sketch should be provided in the field notes so someone who is not familiar with the location can identify each target on the photographs and easily relocate the targets in the field. Offset distances are recorded for targets that are offset. The targets are listed in numerical sequence in the field book. Acceptable [[Media:238.1 Target Location Notes.pdf|examples for recording target notes]] are available.  


The photogrammetry section is available to perform various photographic assignments upon request. In order to properly plan the photographic mission, the Design Division is furnished with basic information regarding the desired photography together with the request for the photography. Aerial photographs are also available for distribution within MoDOT.  Generally, photographs are not furnished to others nor is photography work performed for others.  However, exceptions may be made for special circumstances.
==238.1.6 Aerial Mapping and LiDAR MOU==


==238.1.20 OrthoMosaics==
When mapping becomes necessary beyond the time frame of the annual flight program, district may work with the Central Office Design survey staff to hire an on-call consultant to perform these services. Please refer to [[:Category:134 Engineering Professional Services#134.2.4 Consultant Solicitation and Selection Process – Standard Solicitation Method for On-Call Cost Plus Fixed Fee Contracts|EPG 134.2.4 Consultant Solicitation and Selection Process – Standard Solicitation Method for On-Call Cost Plus Fixed Fee Contracts]].


The photogrammetry section will provide the district with OrthoMosaics on every mapping project. An OrthoMosaic is spacially correct mosaic, which includes the photos for the entire project.  The mosaics are generated  at 0.5 ft. per pixel.  The district design personel can use the mosaics as raster images behind the project corridor line work prepared using CADD tools for the purpose of public displays.
==238.1.7 Orthomosaic==


==238.1.21 Requisitioning Photography and Photographs==
Orthomosaics are a standard delivery with aerial photography mapping. An Orthomosaic is a spacially correct mosaic, which includes the photos for the entire project. The mosaics are generated at 0.5 ft. per pixel. The district Design personnel can use the mosaics as raster images behind the project corridor line work prepared using CADD tools for the purpose of public displays.  


==238.1.8 Requisitioning Historic Photographs==
 
A request for contract prints and enlargements is made using [[Media:238.1 Requisition for Prints of Previous Photography (D-102).doc|Form D-102]].
A request for contract prints and enlargements is made using [[Media:238.1 Requisition for Prints of Previous Photography (D-102).doc|Form D-102]].


[[category:238 Surveying Activities|238.01]]
[[category:238 Surveying Activities|238.01]]

Latest revision as of 11:02, 16 January 2024

Figures
Aerial Target Notes
Second Order Traverse Notes
Examples of Target Location Notes
Example of Polaris Observation Notes
Examples of Vertical Control Field Notes
Form
Form D-102
Survey Coding Sheet
Fig. 238.1.3, Aerial Photography and Control Survey


Aerial Mapping and LiDAR surveys can achieve the same results as conventional topographical surveys by methods which require a minimum of fieldwork. Airborne LiDAR sensors are used by companies in the remote sensing field. It can be used to create DTM (Digital Terrain Models) and DEM (Digital Elevation Models). This is a common practice for larger areas since a plane can take in a swath 1 km wide in one flyover. Greater vertical accuracy can be achieved with a lower flyover and a narrower swath, even over a forest, where the height of the canopy as well as the ground elevation can be determined. Conventional surveys require numerous field measurements to obtain the same data and information.

238.1.1 Surveys Adaptable to Aerial Mapping and LiDAR

Projects with certain physical characteristics are adaptable to aerial mapping and LiDAR surveys. The districts must make the judgment, based on their knowledge of the requirements of each project, whether a conventional or aerial mapping and LiDAR survey best satisfies the need. Factors that influence this decision include:

  • Scope of the project: The use of aerial mapping and LiDAR methods, in almost all cases, will result in the most economical survey for projects encompassing larger areas. Conversely, smaller projects are best suited for field surveys. It is difficult to provide a quantitative guideline to determine which projects fall into which category. Generally, it is better to field survey projects that are shorter than 1300 feet. Aerial mapping and LiDAR projects should be reviewed to determine the best application of LiDAR that will meet the project needs and budget.
Rough terrain with heavily timbered areas
  • Type of project: The project's scope will usually be the best guide for the type mapping needed. Urban enhancements of existing structures may lend themselves to a terrestrial or mobile type of collection for the best results. Where a cross country new alignment would be much better suited for aerial platform like a fixed wing aircraft or helicopter.
  • Terrain: Projects with terrain that is difficult or impossible to field survey will be surveyed by aerial mapping and LiDAR methods. These include projects in highly developed areas, extremely rough terrain, heavily timbered areas as well as bridge surveys for large streams.
  • Time consideration: Time sensitive projects will be field surveyed, because of the lead-time necessary for aerial mapping and LiDAR surveys. Table 238.1.1 shows guidelines to determine what type of survey best suites a project.

Table 238.1.1

Aerial Mapping and LiDAR Survey Versus Conventional Survey
Aerial Mapping and LiDAR Conventional
Wide Corridor Projects Resurfacing Projects
Relocation Shoulder Widening Projects
Large Area Planimetric Surveys Small Area Planimetric Surveys
Large Bridge Replacements Small Bridge Replacements
> 1300 ft. < 1300 ft.
Interchanges -
Rough Terrain -


In addition, district personnel requesting mapping should discuss project specifics with the aerial mapping and LiDAR personnel when determining which method of survey better suits the project.

238.1.2 Stages of Aerial Mapping and LiDAR Services

Data acquisition for aerial mapping and LiDAR surveys are provided by professional consulting services. These professional consultant services are managed by Design Division. These services are provided via the “Annual Flight Program Contract” and the following sequential stages must be coordinated between the district and Design Division:

1. Recommendations for the flight program
2. Mapping limit plan
3. Accuracy planning
4. Consultant selection
5. Quality control on projects
6. Review and quality checks on aerial mapping and LiDAR survey data
7. Furnishing electronic data to the district.

238.1.2.1 Recommendations for Flight Program

The district recommends projects for the flight program each year at the request of Design by the last day of September. Projects recommended for mapping are those that a location study, if necessary, has been approved, or projects for which this will be completed in time to obtain the data during the flying season (approximately December 15 to April 15). Normally, projects that are in the design year of the approved STIP are considered, but other projects may be considered if conditions warrant.

238.1.2.2 Flight Planning

Design performs flight planning, but information from the district is necessary to efficiently plan the the aerial mapping and LiDAR mission. The district furnishes information including the location of the proposed improvement indicated in a CADD drawing file, and the desired accuracy. Mapping and photography limits are to be submitted electronically using CADD software and ProjectWise.

It is desirable to limit the aerial mapping and LiDAR corridor to only that area that is necessary for the design of the project. The district's recommendation regarding the type and extent of aerial mapping and LiDAR survey data coverage will consider the following:

  • For planimetric coverage, corridors will include all features that may affect design considerations and right of way takings. Planimetric corridors do not have to be connected but must be within the area in which horizontal controls have been established.
  • For terrain coverage, corridors will be limited to the area necessary for earthwork computations. Generally, this area is within the limits of proposed right of way. Terrain corridors do not have to be connected but must be within the area in which horizontal and vertical control have been established.
  • Generally, corridor requests do not include areas for drainage computations. Keep in mind that aerial mapping and LiDAR data should be supplemented with conventional survey data and shall be verified by the district survey party .

238.1.2.3 Accuracy Planning

To best extract topographic and manmade features from the LiDAR data, three density and accuracy levels are used, as describe below:

Type A, Roadway and Pavement Scans (Mobile, Helicopter Based or Terrestrial LiDAR)
1) Internal Horizontal / Vertical Accuracy of 0.3 ft. at 95% confidence.
2) Maximum point spacing of 0.3 ft. on the full classified LAS file.
Type B, Corridor and earthwork Scans Urban (fixed wing or Helicopter Based Aerial LiDAR)
1) Internal Horizontal / Vertical Accuracy of 0.5 ft. at 95% confidence.
2) Maximum point spacing of 1 ft. on the full classified LAS file.
Type C, Corridor and earthwork Scans Rural (fixed wing)
1) Internal Horizontal / Vertical Accuracy of 0.5 ft. at 95% confidence.
2) Maximum point spacing of 2 ft. on the full classified LAS file.

238.1.2.4 Consultant Selection

Refer to EPG 134 Engineering Professional Services.

238.1.2.5 Quality Control on Projects

Quality control all projects will be done by the Central Office Design survey staff to ensure the data provided meets MoDOT’s needs for engineering mapping and design.

To verify the accuracy of the surface of the delivered aerial mapping and LiDAR, the Central Office survey staff will take check shots along the main alignment of the project at least every 200 ft. and alternate shoot every 400 ft. each side of the main alignment.

To verify the accuracy of extracted features of the delivered aerial mapping and LiDAR, the Central Office survey staff shall take check shots along curb lines, bridge rails, retaining walls and other features with elevation differences that can easily be identified.

238.1.2.6 Review and Quality Checks on Aerial Mapping and LiDAR Survey Data

All quality control will be done using MoDOT's CADD software. Project control shots will be compared to the surface model and topographic and manmade features provided by the aerial mapping and LiDAR consultant and must meet the internal horizontal/vertical accuracy defined by the scope of services at 95% confidence.

A report will be run and kept with the files for the project certifying these accuracies.

Any acceptance of data below these standards will have written documentation explaining the prescence of this data and what resulting developments may be encountered during the design process.

238.1.2.7 Furnishing Electronic Data to the District

All data will be delivered to the districts via ProjectWise. Once all the data has been delivered and has met the quality standards, Central Office will place the file into the districts' ProjectWise folders for access.

238.1.3 Standard Deliverables for LiDAR Data

The consultant shall provide to the Commission the following items:

1) Three ASCII coordinate files all containing the primary control, photo control and check points for the project survey. These files are:
Primary Control File. A file listing control positions by point number, X, Y, and Z values in project units referenced to the Missouri Coordinate System of 1983, the correct zone name (ex. East Zone), with X and Y values modified by the projection factor. This ASCII formatted file will be in the form of: J######.rec.
The Geodetic Control File. A file containing latitude and longitude information for all control points named J######.txt with file format listed on page 3 of Fig. 238.1.3, Aerial Photography and Control Survey. All OPUS solution sheets and/or data sheets from post processed static GPS sessions, calculations for grid and projection factor including the centroid point, mean elevation and the final grid and projection factor will also be listed in this file.
Check Shots File. A file listing quality control positions by point number, X, Y, and Z values in project units referenced to the Missouri Coordinate System of 1983, the correct zone name (ex. East Zone), with X and Y values modified by the projection factor. This ASCII formatted file will be in the form of: J######.txt.
2) MoDOT Survey Report. A MoDOT survey project report for each project. It shall include copies of all inter-visible control survey pair station descriptions along with all benchmark descriptions and field ties. A sketch of each point shall be provided showing the relative location of field ties to the point being referenced. The consultant shall provide a letter certifying that the below mentioned surveying specifications have been achieved for this project. The letter shall document the relative positional accuracies in parts per million, the confidence level in percent and the post adjustment residual values in centimeters that were achieved on this project. If any portion of the survey does not comply with these specifications, a written report substantiating the material variances from the specifications with the responsible surveyor’s signature is required. The Commission reserves the right to disallow variations.
The survey report documents proof of these specifications:
a. Fixed preprocess baseline solutions.
b. Control station relative positional accuracies of 10 ppm in relation to adjacent stations at the 95% confidence level.
c. Post adjustment residual values <3 cm in any dimension for control stations.
d. A dgn file with all survey control points plotted and labeled.
3) An Orthomosaic captured simultaneously with LiDAR or separate aerial sensor, meeting the following requirements:
a. Shall have a resolution of 0.5 ft. per pixel.
b. Shall be tiled, with tiles no larger than 3250 x 3250 pixels.
c. Shall encompass the area requested for mapping.
d. Shall be a geotiff and accompanied by a projection file (.prj).
e. Shall include a shape file indicating the locations of the orthomosaic tiles.
4) LiDAR projects, the following shall be delivered:
a. Data will be delivered in LAS version 1.2 format or newer with the following information.
i. Record return
ii. Intensity
iii. GPS time
iv. Swath line number designation
v. Classification values after trimming (without data voids between swath lines)
0 = raw, never classified
1 = unclassified
2 = ground (i.e. bare earth)
3 = low vegetation
4 = medium vegetation
5 = high vegetation
6 = building
7 = low point
9 = water
10 = bridge
12 = overlap
b. LiDAR Processing Report.
c. Vertical Accuracy Report.
d. A shape file containing numbered LAS tiles.
5) ASCII coordinate file for each project, containing the following items for each point:
a. X, Y, and Z coordinates using the Missouri Coordinate System of 1983, the correct zone name (ex. East Zone), modified by a factor developed by the consultant.
b. Feature code using MoDOT Standard Surveying Feature Codes.
6) Microstation and OpenRoads Designer files to be provided:
a. Provide a Topo_ConsultantName_JOB#.dgn (3D MicroStation file) of all the topographic and manmade survey data collected.
i. All dgn files will be based on modified state plane coordinates, using the projection factor for the project as described in EPG 238.1.4 Datum and Horizontal Control.
ii. Working units: U.S. Survey Foot
iii. Features shall be plotted according to MoDOT CADD Standards. Features to be plotted at 1” = 100’ scale. Standards are available for Openroads Designer located in CADD's ORD Workspace.
Topography Features. The mapping data shall include natural positions on the earth’s surface within the project limits that determine the configuration of the terrain. The positions will be in the form of points and strings that locate vertical and horizontal transitions.
Planimetry Features. The mapping data shall include the positions of all natural and all man-made features within the project limits. The positions will be in the form of points and strings that define the shape, size and position of the features.
b. Terrain and Geometry information files will be based on modified state plane coordinates, using the projection factor for the project as described in EPG 238.1.4 Datum and Horizontal Control.
c. OpenRoads Designer Terrain Models for the entire project. Terrain models should not exceed 200 megabytes.

238.1.4 Datum and Horizontal Control

238.1.4.1 Linear measures

Linear measures will be made in the English System. The base unit will be the United States Survey Foot (and decimal parts thereof).

238.1.4.2 Coordinate System

All coordinates shall be based on the State Plane Coordinate System, North American Datum (NAD) of 1983 (1997) in the appropriate zone for the project.

238.1.4.3 Vertical Datum

The elevations shall be based on the North American Vertical Datum (NAVD) of 1988. The elevations shall be based upon ellipsoidal heights that have been modified by the most current NGS Geoid model.

238.1.4.4 Projection Factor

The consultant is responsible for developing a project projection factor based on the Missouri Coordinate System of 1983 Manual for Land Surveyors.

Scale Factor. Using the most easterly and westerly control points within the project to develop a centroid point for a project. Use the converted English easting of the centroid point in the correct zone formula, below.


Elevation Factor is determined by dividing the ellipsoid radius by the ellipsoid radius plus the mean elevation for the project.


Grid Factor is the result of multiplying the Elevation Factor by the Scale Factor of the centroid point of the project.

Grid Factor = Elevation factor * Scale factor


Projection Factor is the reciprocal of the grid factor.

Projection Factor = 1 / Grid factor

238.1.5 Field Notebooks (Targets)

A separate notebook is used to record the target locations and descriptions. The notes include, for each target, the target numbers, shape of the target and the target ties. A sketch should be provided in the field notes so someone who is not familiar with the location can identify each target on the photographs and easily relocate the targets in the field. Offset distances are recorded for targets that are offset. The targets are listed in numerical sequence in the field book. Acceptable examples for recording target notes are available.

238.1.6 Aerial Mapping and LiDAR MOU

When mapping becomes necessary beyond the time frame of the annual flight program, district may work with the Central Office Design survey staff to hire an on-call consultant to perform these services. Please refer to EPG 134.2.4 Consultant Solicitation and Selection Process – Standard Solicitation Method for On-Call Cost Plus Fixed Fee Contracts.

238.1.7 Orthomosaic

Orthomosaics are a standard delivery with aerial photography mapping. An Orthomosaic is a spacially correct mosaic, which includes the photos for the entire project. The mosaics are generated at 0.5 ft. per pixel. The district Design personnel can use the mosaics as raster images behind the project corridor line work prepared using CADD tools for the purpose of public displays.

238.1.8 Requisitioning Historic Photographs

A request for contract prints and enlargements is made using Form D-102.

Retrieved from "https://epgtest3.modot.org/index.php?title=238.1_Aerial_Mapping_and_LiDAR_Surveys&oldid=53328"