Converting Raster Data to Local Coordinate Systems

End users may require point cloud and raster deliverables in local coordinate systems, aka ground coordinates or local site calibrations, or to debias an orthomosaic to control. In addition to the Reproject LAS PCT, TrueView EVO/LP360 Drone has the capability to scale, translate and rotate point clouds to a variety of local coordinate systems by using a Affine Transform LAS PCT to apply a:

Where LP360 is lacking at the moment are similar tools to apply those transformations to rasters generated by Metashape, PIX4D or other photogrammetric packages that are unable to handle the grid-ground or local site calibration transformations of the apriori positions generated by LP360 Drone. We are actively developing a built-in GUI driven method to simplify this workflow so a user may apply a scale and translate to raster data, typically orthomosaics, but have put together this temporary workflow using a batch script that will help perform this task for you in the interim. This operation will need to be performed on a computer with an actively licensed version of TrueView EVO/LP360 Drone at a license level other than Viewer or Explorer.

Download these files and extract the contents keeping them in the same folder. The location on your machine does not matter so long as the files remain together in the same folder. The raster and PCT may reside elsewhere on your machine.

  • ApplyAffineTransform2Raster.txt (rename extension to .bat)
  • Jsonextractor.txt (rename extension to .bat)
  • ExportENasCSV.xml

The batch file will receive the scale factor and translate values from the exported copy of the Affine Transform LAS PCT you used to scale and/or translate the LAS point cloud. First, setup a point cloud task with the task type for Affine Transform. Use the scale and/or translate values as needed to convert to your local coordinate system or debias your data. Ensure that Maintain Source File Structure to keep your LAS data tiled and that Geotag as Local SRS is checked, unless only debiasing. Run the PCT and then verify you point cloud is correctly placed on the local coordinate system using check points or a visual inspection. Make a copy of your Affine Transform LAS PCT and change the export path to “<LP360_PROJECT_PATH>\LocalSRS\” verbatim, turning off the Maintain Source File Structure option. Export the point cloud task from the Point Cloud Task Manager (PCTM) in xml format and note its location for the next step. When exporting ensure that the your Affine Transform PCT is the only one checked for Export in the Point Cloud Task Manager.

TrueView EVO/LP360 Drone needs to be closed during the batch script execution to allow your license to be available for use by the batch process. You will need to enter a command line entry detailed below:

  1. Open a Command Prompt (Windows Key and type CMD and Enter)
  2. Drag and drop your ApplyAffineTransform2Raster.bat into the console window and press spacebar
  3. Drag and drop your raster file and and press spacebar
  4. Drag and drop your AffinePCT.xml file and press space
  5. If your project is in survey feet type “sf”, or for international feet “ft”, or for meters “m”

Your command line entry should look like this, double check your syntax and press Enter to execute:

"C:\Ortho_Scale_Tool\ApplyAffineTransform2Raster.bat" “E:\Test_Project\Photo_Package\Metashape\Photo_Package_20210802T1112\Photo_Package_20210802T1112_ortho.tif” "E:\Test_Project\Photo_Package\Metashape\Photo_Package_20210802T1112\Affine_Transform_PCT.xml" sf

The local SRS orthomosaic will be generated in the same folder as the input and be called the same name, but with “_localsrs_[m or sf or ft]” appended to it. Example output raster in local coordinate systems:

Photo_Package_20210802T1112_ortho_localsrs_sf.tif

Photo_Package_20210802T1112_ortho_localsrs_sf.tfw

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