> For the complete documentation index, see [llms.txt](https://docs-7.phoenixlidar.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs-7.phoenixlidar.com/lidarmill-desktop/workflow-kk/ground-control/ground-control-points-gcps.md).

# Importing Ground Control Points (GCPs)

There are two ways to differentiate high accuracy survey control points - Ground Control Points (GCPs) and Survey Checkpoints (SCPs).

* GCPs and SCPs are generally collected at the same time, using the same methodology. 
* GCPs are surveyed control points used for data adjustments, and SCPs are surveyed control points used for accuracy reporting. 
* GCPs utilized for data adjustments should not be used to validate the accuracy of the data product. 

GCPs can be either a TXT or CSV file. To load GCPs, use **File->Open**. SpatialExplorer will then ask you to assign fields (name, X, Y, Z, type) to the columns in the file. You also need to specify which row contains the first GCP in order to skip any header or metadata.

![](/files/-M_7aLQcKG3MsPyd5vQz)

Ensure the Coordinate Reference System (CRS) is properly configured to match the CRS that the GCPs reference. For configuring the CRS menu, refer to [project setup](/lidarmill-desktop/workflow-kk/project-setup.md). 

Visually verify the GCPs are properly georeferenced:

![GCPs set as control, check, and unused. ](/files/-M_7b0AbhsQmS3hJzg8l)

GCPs have a type attribute that can be set to **control**, **check**, or **unused**. Control points are used for data adjustments, whereas check points are just used for accuracy reporting and evaluation. **Control** points will appear orange in the point cloud, **check** points will appear blue, and **unused** points will be grey. 

You can find more information on GCPs [here](https://www.phoenixlidar.com/wp-content/uploads/2020/11/Survey-Ground-Control-Recommendations.pdf).