How to include GCPs in the Project

Pix4Dmapper can process projects with or without Ground Control Points (GCPs). Accurate GCPs increase the global accuracy of the project.  

Ground Control Points (GCPs) can be:

  • Measured in the field with topographic methods. For more information: 202557489.
  • Extracted from existing geospatial data.
  • Extracted from Web Map Service (WMS). For more information: 202560149.

There are several ways to add and mark GCPs depending on:

  • The initial geolocation of the images.
  • The coordinate system of the original images.
  • The coordinate system of the GCPs.

The table below presents the different cases that can occur and which method can be used to add and mark GCPs.

Images \ GCPsWith known coordinate systemWith arbitrary coordinate system
With geolocation in a known coordinate system Method A / Method C Method B / Method C
With geolocation in arbitrary coordinate system  Method B / Method C  Method B / Method C
Without geolocation  Method B / Method C  Method B / Method C

For more information about the coordinate system of the GCPs: 202557749.
For more information about the coordinate system of the images: 202557639

Method A This method is used when the image geolocation and the GCPs have a known coordinate system that can be selected from Pix4Dmapper's database. The two systems do not need to be the same as Pix4Dmapper is able to do the conversion between two different known coordinate systems.

This is the MOST COMMON CASE. It allows the user to mark the GCPs on the images with little manual intervention. However, this method is not suited for "overnight" processing during which the different processing steps start automatically in a row and do not require any supervision by the user.

GCPs_A.jpg

Method B  This method can be used for the following cases:
  • The initial images are not geolocated: When no GPS was used and no coordinates were given to the images. The GCPs can be in any coordinate system.
  • The initial images are geolocated in an arbitrary coordinate system: This is common when dealing with terrestrial imagery or when reconstructing small objects. The GCPs can be in any coordinate system.
  • The GCPs are in an arbitrary coordinate system: The coordinate system of the image geolocation is not relevant.

It allows the user to mark the GCPs on the images with little manual intervention when the images are not geolocated or when the images or GCPs are geolocated in an arbitrary coordinate system. However, this method is not suited for "overnight" processing during which the different processing steps start automatically in a row.

GCPs_B.jpg

 
Method C This method works for any case, no matter the coordinate system of the images or GCPs, but it requires more time to mark the GCPs on the images. The advantage of this method is that after importing the images and the GCPs, the processing can be done without any intervention by the user. 

It is the best choice for "overnight processing" (i.e  leaving the PC processing without any supervision). However, it requires more manual intervention to mark the GCPs on the images. 

GCPs_C.jpg

  

Method A

This method is used when the image geolocation and the GCPs are in a known coordinate system that can be selected from Pix4Dmapper's database. The two systems do not need to be the same as Pix4Dmapper is able to do the conversion between two different known coordinate systems.

This is the MOST COMMON CASE. It allows the user to mark the GCPs on the images with little manual intervention. However, this method is not suited for "overnight" processing during which the different processing steps start automatically in a row and do not require any supervision by the user.

 

Instructions

1. Obtain GCPs measurements in the field or through other sources: 202557489
2. Add / Import  the GCPs with the GCP / MTP Manager WITHOUT marking them: 202560039.
3. On the Menu bar, click View > Processing. The Processing bar appears at the bottom of the Main Window.
4. Select 1. Initial Processing and deselect 2. Point Cloud and Mesh and 3. DSM, Orthomosaic and Index.
5. Click Start.

6. Once Initial Processing is completed, mark the GCPs with the rayCloud: 202560769.
7. Click Process > Reoptimize.
8. (optional) Regenerate the Quality Report by clicking Process > Generate Quality Report.  

 

Method B

 This method can be used for the following cases:

  • The initial images are not geolocated: When no GPS was used and no coordinates were given to the images. The GCPs can be in any coordinate system.
  • The initial images are geolocated in an arbitrary coordinate system: This is common when dealing with terrestrial imagery or when reconstructing small objects. The GCPs can be in any coordinate system.
  • The GCPs are in an arbitrary coordinate system: The coordinate system of the image geolocation is not relevant.

It allows the user to mark the GCPs on the images with little manual intervention when the images are not geolocated or when the images or GCPs are geolocated in an arbitrary coordinate system. However, this method is not suited for "overnight" processing during which the different processing steps start automatically in a row.

Instructions

1. Obtain GCPs measurements in the field or through other sources: 202557489
2. On the Menu bar, click View Processing. The Processing bar appears at the bottom of the Main Window.
3. Select 1. Initial Processing and deselect 2. Point Cloud and Mesh and 3. DSM, Orthomosaic and Index.
4. Click Start.

5. Add / import and mark ONLY of the GCPs in the rayCloud202560109.
6. After having imported the GCPs and having reoptimized the reconstruction, add / import the remaining GCPs with the GCP /MTP Manager WITHOUT marking them: 202560039.
7. Mark the GCPs in the rayCloud: 202560769.
8. Click Process > Reoptimize.
9. (optional) Regenerate the Quality Report by clicking Process > Generate Quality Report.  

 

Method C 

This method works for any case, no matter the coordinate system of the images or GCPs, but it requires more time to mark the GCPs on the images. The advantage of this method is that after importing the images and the GCPs, the processing can be done without any intervention by the user. 

It is the best choice for "overnight processing" (i.e  leaving the PC processing without any supervision). However, it requires more manual intervention to mark the GCPs on the images. 

 

Instructions

1. Obtain GCPs measurements in the field or through other sources: 202557489
2. Add / import all the GCPs with the GCP /MTP Manager202560039.
3. Mark the GCPs on the images with the Basic GCP/MTP Editor202560099.
4. Process all three steps of processing:202557519.

 

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