Surveying With Any GPS Equipment and Exporting to a gps file for the Trimble FMX

Question:
Can I Survey With Any GPS Equipment and then use OptiSurface Designer to export to a .gps file for the Trimble FMX?

Issue:
The gps point are in WGS84 geographic projection, after that we reproject the pts in nad83 UTM18N (Canadian and American projection) to have the coordinate in meters. After that we bring the MB back to 0:X and 0 : Y, we integrate the points in OptiSurface Designer with a txt file.

When we export the proposed design, and integrate our plan into the trimble system it opens very well into the tractor. But last week, we discovered that the field projected by the plan in the trimble system is actually slightly shifted from reality. The farther we were from our Master Benchmark, the more we seemed to be out of position. Also, the cut and fill on the existing topography is not at the right place. For example, in a field that is 1.5 km long, we were off our position by about 20 meters once at the end.

We did a topography with our system behind the tractor to see if the tractor points are shifted from our points and this is what happened. I think the points are shifted from reality and we think it's a projection problem, but we don't know for sure, and we put the MB for both files at 0 : X and 0 : Y

Answer:
The Trimble Field Level2 system with the .gps file (FMX) uses a special coordinate system where X and Y are derived from a local tangent plane with the origin at the master benchmark and elevation (Z) is derived from the geoid corrected WGS84 coordinate.
 
Using UTM coordinate system is not the same and you can end up with the design being skewed or rotated by up to 15m as you move 1km away from the master benchmark. This is a problem for Multiplane designs but even more problematic for designs with steeper slopes because a 15m horizontal error on a 1% slope can mean 150mm more soil cut or filled than required.   

There are two solutions to solve this problem:
1) Resurvey the topography with the  Trimble Field Level2 survey plugin. or
2) Transform the current coordinates you have from the coordinate system you have to the same one the Trimble Field Level2 system uses.

In future versions of OptiSurface Designer (eg V2.0) we would like to support the on the fly coordinate transformation during export but for now you can try a coordinate transformation software such as: 
Converting Latitude/Longitude to Easting/Northing


Tips and Tricks

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

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