Can Drone Or LIDAR Surveys be used with OptiSurface?

Last Updated: 13 June 2017          For: OptiSurface Designer V1.4 and higher


Answer:
OptiSurface Designer can import topography data from aerial and drone surveys that use LIDAR or photogrammetry.  However, we are cautious about using this for landform designs because the vertical accuracy of this data is typically +/-50mm or -+2 inches.

For ditching, surface drains or tile/pipeline applications +/-50mm is probably fine.  However, OptiSurface landform designs typically move less than 50mm or 2inches on average over a field.  Therefore, if the survey data has this level of inaccuracy to start with you could end up moving 200% more soil than required.

There can also be coordinate system differences between the topographic data and the machine control system which can introduce horizontal and vertical biases or offsets between the survey and machine control system (see Coordinate System Differences with Different GPS Systems).

Therefore, currently we recommend topography data from aerial and drone surveys can be used to do preliminary landform designs, drainage analysis, runoff analysis but not for final designs.

If you can get the data into a text file with the format of x, y, z then OptiSurface will import it.  However, LIDAR and photogrammetry data is often very dense and OptiSurface Designer can filter down the point number to 30,000 per field to ensure faster operations/calculations.


Aerial Survey Accuracy


This is copied from the Sensefly (leading drone survey company) FAQ

Q:  What kind of positional accuracy can I expect?

A:  The accuracy of the orthomosaics and the digital surface models (DSMs) produced by professional photogrammetry software such as Pix4Dmapper (optional with every senseFly drone) depends on various factors, including: flight height, light conditions, availability of textures, image quality, overlap, and the type of terrain being mapped.

In standard conditions, flying an eBee or eBee Ag at an altitude of 100-150 metres (328 - 492 ft) above natural terrain, with an image overlap of between 50% and 70%, and not using any ground control points (GCPs), a relative accuracy of 10 cm (3.9 in) and an absolute accuracy of 1 - 5 m (3.3 - 16.4 ft) can be expected at the location of the found matching points, when using Pix4Dmapper. Between these matching points the accuracy may vary.

These figures are vastly improved by using GCPs, with absolute accuracy then possible of down to 3 cm (1.2 in) / 5 cm (2 in).

As for the eBee RTK, this survey-grade mapping drone is capable of achieving the same absolute accuracy - of down to 3 cm (1.2 in) / 5 cm (2 in) - without the need for GCPs.

Read the eBee RTK Accuracy Assessment whitepaper.
https://www.sensefly.com/fileadmin/user_upload/sensefly/documents/eBee-RTK-Accuracy-Assessment.pdf

(Please note that senseFly cannot guarantee in any way the quality and accuracy of your output files.)

This video shows how to use Ground Control Points. It would be also useful to use points collected as you drive between the GCPs as independent checkpoints as explained in the video below:




Aerial Survey Accuracy Test

If you wish to test the accuracy of your aerial survey with ground based survey we recommend a procedure like this:
  1. We recommend covering an area at least 1km x 1km.
  2. Place at least 10 control points over the area. One at each corner, one a the center and then the five more spread over the field. There should probably be 9 (3 x 3), 16 (4 x 4) or 25 (5x5) ground control points depending on field size.
  3. Surveyed these control points as benchmarks on the Trimble Field Level 2 system or the system you are planning on conducting the earthworks with because they can use different horizontal and vertical coordinate systems.  
  4. During the Sensefly post processing, you would need to get the x, y, z of these same points. Then in a spreadsheet we could compare the x, y, z.
  5. Do not carry out any correction/adjustments to the Ground Control Points but check the difference in x, y, z at each point.
  6. Then carry out a survey adjustment on the aerial survey with half the Ground Control Points, then the difference in x, y, z at the remaining check points.
Note that the Trimble Field Level 2 System uses a slightly different coordinate system and transformation from another coordinate system could produce some errors. See this article for more info: Coordinate System Differences with Different GPS Systems





Tips and Tricks

  1. Trimble Field Level II Do Not Show the .gps File
  2. Minimum Recommended Smoothing Distance For Export To Trimble Field Level 2
  3. GPS Base Station Setup For Best Vertical Accuracy
  4. How to Survey with Trimble FMX
  5. How Easy is OptiSurface to Use for the Average Farmer?
  6. Balancing Earthworks in the Field
  7. Landform Design Slopes and Smoothing
  8. Export Proposed Topography to AutoCAD
  9. Surface Irrigation Designs with Variable Slope
  10. OptiSurface Designer Import and Export Format
  11. Importing Multiple Survey Files to OSD
  12. Can Drone Or LIDAR Surveys be used with OptiSurface?
  13. Calculation Grid Spacing and Export Grid Spacing
  14. How to Survey a Field for Landforming Design
  15. Loading .gps File in FmX
  16. Designing a Field in Sections
  17. Using an Old OSD File versus a New Survey
  18. No Master Benchmark on Imported Survey File
  19. Displaying Secondary Benchmarks
  20. Import Error for xyz File Due to Encoding Format
  21. OptiSurface4D: Bounded By Ridges
  22. Can OptiSurface handle curved rows in Drainage Analysis & Runoff Analysis?
  23. Reverse Grades to Main Slope
  24. Measuring Culvert Invert Level
  25. Surveying a 1000-Ha Field
  26. GPS Coordinate System Check
  27. Does A Normal UTM Zone Coordinate Need To Be Trimmed To x Digits?
  28. Can You Import Data Directly From GPS System?
  29. Converting Latitude/Longitude to Easting/Northing
  30. Surveying With Any GPS Equipment and Exporting to a gps file for the Trimble FMX
  31. DGPS Post Treating System with 5cm Precision For Landforming
  32. Exporting to Trimble FMX Field Level
  33. Can I Survey with a GPS System on an ATV?
  34. Standard NMEA GPGGA txt File to Import into OptiSurface Designer
  35. Importing .csv File from APEX to OptiSurface Designer
  36. 900 Acres: Cut that large survey down.
  37. Export Options for Data Layers
  38. Import Two or More Survey Files to Reach Minimum Area
  39. Different Row Slope Directions In One Field
  40. Does OptiSurface allow for multiple grade breaks per design, taildrains roads, pads etc?
  41. Can I View DTM/Topography In Plan View Or 3D Type View When Doing A Design?
  42. Adjust the Bands in the Legend
  43. Design for a 1000-Ha Field
  44. Would It Be Possible That The Numbers In The Boundary Zone Appear In The New Subzone Created?
  45. Grade Of Best Fit And Splitting The Field Into Boundaries
  46. Acceptable Minimum Slopes
  47. Incorrect Area in OptiSurface
  48. Supported Units of Measurement of OSD
  49. Valley Subzone Not Behaving as Expected
  50. Difference Between Breaklines And Subzones
  51. Alignment of Furrow/Bed Direction with OptiSurface Design Mainslope Direction
  52. Subzones Settings Over Ride Boundary Zone Settings
  53. Printing the Maps
  54. Print Size
  55. Colored Printing

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