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Control Points (GCPs and CHPs) file format for data processing


We’ve made it as easy as possible for you to upload your control point coordinates no matter what type of control point marker you use. All you need is a simple text file, in addition to your photos, for processing. You or your survey team will be able to create this text file in a couple of minutes!

Our Skycatch data processing pipeline accepts two types of control points: ground control points (GCPs) and checkpoints (CHPs). (TEST)

  1. GCPs are used during the data processing step to accurately georeference and calibrate your images.
  2. Checkpoints (CHPs) are not taken into account for processing and calibrating your models; CHPs’ coordinates are used to assess the accuracy of your project by comparing its true predetermined locations with the positions of processed ground control points. CHPs help you see the amount of error in a project. 
    • Note: Checkpoints are currently only used for verification purposes if the user reports an issue with the accuracy of their dataset, so you will not automatically receive an accuracy report if you choose to upload control points with a dataset. 

Here are a few notes about using control points with Skycatch:

  1. The coordinate system you define for your site and the coordinate system for your control points must be the same. They should either both be in a GPS coordinate system (lat, long, alt) or planar coordinate system (x, y, z).
  2. Control points should have survey-grade coordinates as this will have a high impact on the accuracy of the data processing.
  3. You must manually upload and mark your control points by following these instructions.

Control Points processing with local coordinates

You can submit control points in a GPS coordinate system (lat/lng/alt) or a planar coordinate system (x, y, z) in our web uploader. If you are using local coordinates, the site coordinate system can consume a localization file (.tp3 or .gc3). You can verify that the coordinates are in the correct location when reviewing the data before upload - the control points and the photos should be in the same location.

 

Save your Control Points File with a .csv file extension

The uploader only accepts a .csv file extension for control points. Mac users can right-click a file folder and select "Rename" to rename the file extension. Windows users can follow the instructions provided here to rename their file extensions.

 

How to Format Data In Your Control Points File

The control points file should be a .csv file format and with headers like the following:

“name, type, y, x, z” or “name, type, lat, lng, alt”

 

Column Header Description

1. "name" - the name of the control point

2. “type” - GCP or CHP

3. "y" or "lat" - Northing or Latitude value

4. "x" or "lng" - Easting or Longitude value

5. "z" or "alt" - Orthometric Height (Elevation) or Height above the ellipsoid

 

Control points file examples

Here is an example of a .csv control points file in a GPS coordinate system, with Skycatch control point marker ID tags:

You can download the following example files to use as a template for formatting your control points. Simply replace the data under the headings row with your own data.

 

  1.  GPS Coordinates Example.csv
  2. Planar Coordinates Example.csv
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