QUESTIONS & ANSWERS FOR. ORTHOPHOTO & LiDAR AOT

Transcription

1 QUESTIONS & ANSWERS FOR ORTHOPHOTO & LiDAR AOT Question# 1. Section 3.2 Will the imagery be clipped to the 1000m boundary? If so, what color will be used for null valued pixels? Yes, the imagery will be clipped to the 1000 meter boundary, 500 meters on either side of the highway centerline. The value for those no data pixels outside the corridor will be 255, 255, 255. Question# 2. Section a. 2-4 control points per priority area was mentioned for a horizontal accuracy check. Will the same points be used for the vertical check? Vertical accuracy can be assessed from the main project ground control and the Quality Control ground control points that have been already set. These points can be used for horizontal and vertical assessments. b. Has the Vermont Agency of Transportation, Survey Section already completed the survey or will the QC vendor be involved in point selection? Quality Control points have already been defined and targeted in the imagery, and surveyed by the VTrans Geodetic Survey Unit. Question# 3. Section a. Will the bare earth points be tested against the v13 accuracy specifications? It is not clear the v13 accuracy specifications listed in the question. Question# 4 Section a. Given the simultaneous acquisition of imagery and LiDAR will Fugro be using the LiDAR data to rectify the imagery or producing a Digital Surface Model? The LiDAR data will be used in the creation of a terrain model to rectify the imagery. Fugro will be providing a Digital Terrain Model to VTrans, based on the processed LiDAR data acquired for this project. Question# 5. Page 2, point of the RFP states that QA/QC shall be performed on a tiled digital terrain model (DTM). Is this dataset to be provided as a RASTER model or a TIN model?

2 The Digital Terrain Model (DTM) will be provided as an ASCII file representing the XYZ values and in a format that a RASTER or GRID can be generated. Question# 6. Page 7, point of the RFP states that approximately 122 miles of highway corridor, 1000 meters wide, will be involved in this project. Without allowing for tiles partially covering areas outside these corridors, this works out to +/- 350 tiles. Allowing for partial tiles may increase that number to more than 500. a. What is the actual number of 750 X 750 m tiles? Is a grid index already defined for these? If so, please provide a copy of the index if it is available in digital form. A 750 meter X 750 meter grid has been defined for the project area. There are 652 tiles (750 meter X 750 meter grid) that intersect the 1000 meter project area swath. There are a considerable number of tiles that only a small fraction of the tile intersects the project corridors. Copies of the 750 meter X 750 meter grid Project750Grid and the corridor project area have been posted in shapefile format to the VTrans FTP site at the following directory: ftp://vtransmap.aot.state.vt.us/maps/vtrans_data_irene/orthophoto_lidar_corridorproject_qaqc/ b. Are partial tiles along the edges of the actual corridors to be processed and QA/QCd also? Yes, there will be imagery within the 1000 meter corridor of the project area and this may be split by tile boundaries. This will create many tiles that are partially covered with imagery and this data does need to be included in the QA/QC. Question# 7. Page 8, point mentions among other things that The difference between the minimum and maximum value in a RBG triplet of any nearly neutral objects within the image shall be less than 10, with a preferred value greater than 5 What is meant by a neutral object? A neutral object is a identifiable feature within the image that has uniform and consistent color, such as a section of pavement or top of a building. c. An object whose color is some shade of gray, with low or zero color saturation? The color of a neutral object does not necessarily need to be a neutral color or have low color saturation.

3 d. An object with a uniform color? Yes. e. Does VTrans have any field verified control points, or a list of known locations having known color characteristics that could be used to verify the orthophotography? Question# 8. Page 8, point states that excessive tilt in buildings and bridges shall be corrected. Does VTrans have a standard, in pixels or units of length for what constitutes allowable vs. excessive building tilt? Question# 9. Page 9, point states among other things that All fiducial mark images shall be visible, clear and sharp Typically, fudicial marks are removed from digital orthophoto mosaics. f. Does this mean that the digital orthophoto mosaic purchased by VTrans includes fiducial marks? No, fiducial marks will not be present in the digital orthophoto mosaic, but may exist in the original images acquired for this project. Fiducial marks are sensor dependent, but must be removed from the final orthophotos. g. Or does this mean that the source non-orthorectified photographs/images used to create the digital orthophoto mosiacs are also to be checked for quality? If so, specify the number of photographs/images that are to be checked. This project does not include the QA/QC of the original non-orthorectified imagery. Question# 10. Page 9, point states that metadata shall be complete and appropriately documented. Does VTrans require the use of any particular metadata standard, such as the US government s FGDC? Metadata for this project will be FGDC compliant. Question# 11. Page 8, point specifies horizontal accuracy requirements for orthophotos and states that The QC Contractor will be given a set of between two (2) and four (4) control points collected by the Vermont Agency of Transportation, Survey Section within each corridor acquisition area for use in horizontal accuracy assessments. The QC Contractor is to use these control points in the performance of an Independent Horizontal Accuracy Evaluation

4 h. Will these control points likely be visible on the imagery, either because they represent landmarks or were marked with targets on the ground prior to image acquisition? Ground control points have been targeted, represented by a white X, V or T on the ground. i. How many control points are there in total? There are 34 control points used for the rectification of the imagery and there are an additional 34 ground control points that have been reserved for QA/QC. The 68 points have been targeted and should be fully visible in the imagery. j. Does independent verification exist to validate that the quantity, density and distribution of control points are appropriate to calculate the accuracy per the ASPRS Class II horizontal RMSE standard? k. In your estimation, will there be a need to field survey additional horizontal control points? If additional horizontal control is required, this information will be provided by the VTrans Geodetic Survey Unit. Question# 12. Page 9, point specifies vertical accuracy standards for the LiDAR data. l. Are the control points mentioned in point on page 8 to be used for this purpose? The QA/QC ground control points referenced in section are specific for the horizontal accuracy assessment, but these points do have vertical data associated and can be used for assessment of the LiDAR data. m. Does independent verification exist to validate that the quantity, density and distribution of control points are appropriate to calculate accuracy per the ASPRS Class I horizontal and vertical RMSE standard? n. In your estimation, will there be a need to field survey additional horizontal and vertical control points? Additional field survey will not be needed from the vendor. Additional ground control points will be collected by the VTrans Geodetic Survey and VTrans Mapping Units and provided to the QA/QC vendor.

5 Question# 13. In sec five sections of 1000m wide highway corridors are described. In you indicate there will be 2-4 control points for each section provided to test the horizontal accuracy of the orthos and that the tested accuracy should exceed ASPRS Class II accuracies. However, a minimum of 20 points are needed to perform this test in a specific area. So if there are 20 points in the entire data set, this statistical test would be valid. But it is not possible to perform this statistical test within each section with only 2-4 points. Are there additional control points available within each section to perform valid accuracy estimations or are you assuming we will simply test the entire data set with the available points (a min. of 20 is required to perform a valid statistical test)? Additional control points will be collected and provided by the VTrans Geodetic Survey and the VTrans Mapping Units to meet the minimum required points to perform the accuracy assessment. Question# 14. In section similar accuracy tests are requested for the Lidar data. Vertical and horizontal accuracy tests need a minimum of 20 points in each area or ground classification type (bare, short grass, weeds, etc.). Will sufficient control points be available to test the Lidar horizontal and vertical accuracy as specified in ASPRS and FEMA's guidelines? Sufficient points will be provided for the core hard surface areas related to the transportation infrastructure and the adjacent areas of grass/weed cover types. Ground control points for the other main cover types will not be provided to the same level and will have a smaller representative sample of points. Question# 15. In section you ask that the LAS Bare Earth points be tested to meet or exceed the FEMA guidelines. FEMA requires bare earth DEM (min of 5m spacing) be tested using NSSDA. However, this solicitation elsewhere requires that ASPRS test procedures be followed. Can you clarify? The LiDAR will be tested to assure it meets or exceeds the ASPRS Class 1 vertical accuracy of +/ centimeter RSME at 95 confidence level, as defined in Section The horizontal accuracy of the LiDAR will meet the ASPRS Class 1 accuracy for 1:600, as defined in Section The ASPRS specifications will be used for accuracy assessment for this project. Question# 16. Further, FEMA requires a min. of 20 evenly distributed control points in each main category or ground cover classification. Will this be possible with the available ground control? If not, can you indicate which FEMA specifications should be met or exceeded? Sufficient points will be provided for the core hard surface areas related to the transportation infrastructure and the adjacent areas of grass/weed cover types. Ground control points for the other main cover types will not be provided to the same level and will have a smaller representative sample of points.

6 Question# 17. In you ask the DTM accuracy be assessed but no accuracy standard is specified. Can you clarify? The Digital Terrain Model (DTM) will be tested to assure it meets or exceeds the ASPRS Class 1 vertical accuracy of +/ centimeter RSME at 95 confidence level, similar to the LiDAR files defined in Section Question# 18. In secion 4 the solicitation says the bidder must specifically identify and itemize pricing estimates for each activity contained in the proposal and that failure to submit complete and comprehensive pricing will be a default. Yet the pricing sheet indicates you only want 3 prices for general activities and deliverables (and prices for optional items). Can you explain further what detailed activity pricing you need and how do you want that presented on the pricing form? The pricing estimates relate to the items listed in Section 4 and include the Base-1, Base- 2, and Base-3 defined in the matrix in Section 4 on Page 11 of the RFP. There are also optional service items that may be proposed by the vendor and articulated in the estimates. Question# 19. What was the monetary value of the original contract, to produce the 3 product datasets that are to be reviewed? The project cost with Fugro for the 7 corridors comprising approximately 122 miles is $351, Question# 20. How many corridor segments are there? There are 7 corridors. Question# 21. Will Vermont provide a geographic file (e.g. shapefile) of the contracted corridors area of coverage? Yes. A corridor polygon shapefile will be provided. Question# 22. What is the total length of each corridor or all corridors combined? The total length of the corridors combined is miles. A breakdown by corridor by mileage and percent of the total is below: Priority Corridor Mileage Percentage 1 VT-100 (north) from US-4 intersection in Killington to Rochester Village %

7 2 VT-100 (south) from Plymouth to US-4 intersection in West Bridgewater % 3 VT-9 Marlboro to Brattleboro % 4 VT-12A Randolph to Northfield % 5 VT-11 Andover to Chester % 6 US-4 Rutland City to Hartford % 7 VT-107 Stockbridge to Bethel % Totals % Question# 23. What is the maximum allowable sun angle in the Fugro imagery project? Sun angles greater than 30 degrees were required for imagery acquisition. Question# 24. We assume Fugro will be primarily responsible for edge-marching and color correcting the orthophotography tiles and the responsibility of the QC vendor will be to QC this work. Please confirm. Yes, Fugro will be performing the edge-matching and color correction of the orthophotography. The QC vendor will review this work based on the specifications outlined in the section 3.2 of the Scope of Work. Question# 25. In addition to the GeoTIFF tiles, will Fugro also be delivering ortho data sets merged into corridor-wide files? If so, will these be MrSID or another compressed format? No, all the imagery to be delivered will be tiled and not provided as a corridor mosaic. No imagery has been specified to be delivered by Fugro in compressed format. Question# 26. What was the bid price of Fugro s work? The project cost with Fugro for the 7 corridors comprising approximately 122 miles is $351, Question# 27. Has Fugro completed their work? Question# 28. Is Fugro classifying the point cloud points or is that the responsibility of the QC vendor?

8 Fugro will be classifying the point cloud and only QA/QC of this is necessary by the QC vendor. Question# 29. In the QC rfp the near infrared band is mentioned as an option. Should we include QC of this in the bid cost as a separate item? The near infrared (CIR) is being delivered as the 4 th band in the orthophotography. Question# 30. How many ORTHO/lidar tiles are there? There are 652 tiles (750 meter X 750 meter grid) that intersect the 1000 meter project area swath. There are a considerable number of tiles that only a small fraction of the tile intersects the project corridors. Question# 31. Do the ortho/lidar tiles use the same tiling system? Yes. Question# 32. Will the winning vendor be provided a tile grid? Yes. The 750 meter X 750 meter tile and the corridor 1000 meter project areas will be provided to the QC vendor. Question# 33. Is fieldwork expected to QC and verify the accuracy of LiDAR and/or orthophotography? Question# 34. Sec Will the control points chosen by VTrans for horizontal accuracy QC be chosen to be photo-identifable in the orthos? Will those points also have a field-measured Z- value measured by VTrans accurate to project standards? Is fieldwork expected? Field work is not expected. Question# 35. Will the QC vendor receive the draft orthos, LiDAR and DTM at the same time?

9 It is anticipated that the products will be provided at the same time on a corridor by corridor basis, although the delivery details have not been finalized with Fugro.