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

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