Including Control Points in the DataHub Upload (Ground Control Points and Checkpoints)

 

This article details the step-by-step process of uploading control points in DataHub.

 

What are Control Points?

In land surveying, control points are points in space which have unique and known precise coordinates based on a reference system.  They are the "ground truth" which are used as basis for interpolation or accuracy checks (see: FAQ: What Are Control Points (GCPs And CHPs) And How Do I Lay Them?)

This article help you upload control points as part of your photogrammetry datasets.

 

How to upload Control Points in DataHub

1.  Upload your datasets in the respective DataHub site as you normally would.  For more information about this, kindly follow the guide on uploading photogrammetry datasets.

2.  Under the "options" menu, select the option "Mark GCPs + Checkpoints"

 

3.  A pop-up will appear to let you upload Control Points.  You can neither manually enter your control points' data or upload a CSV file containing the coordinates and other important information (see Control Points (GCPs And CHPs) File Format For Data Processing).

Sample csv files are available for download in the pop-up--click on "GPS Coordinates (WGS84)" or "Planar Coordinates" to access them and edit accordingly.

 

 

4.  Make sure to select the proper coordinate system of the control points.  Selecting an inappropriate coordinate system will introduce issues either in the image marking process or in the processing of the control points.

 

 

5.  Now it is time to mark the control points in the images.  This will require input from the uploader to declare which object captured by the drone correctly corresponds to the control point data.  If the control point coordinates and coordinate system are correct,  DataHub will automatically filter the photos to display the photos nearest to the coordinates of the control point.  Mark the control points in the images as accurate and precise as possible, you may pan and zoom using your mouse.  A minimum of three marked images are required per control point; correctly marking more than 3 will increase accuracy of your control points.

 

 

6.  Once you have correctly marked the images, the Done button will be enabled and you are now able to proceed with your upload.

 

 

7. The DataHub uploader will display the positions of your control points according to your markings.  You may use this visualization to assess the distribution of your control points

 

 

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