# Adding Ground Control Points and Polygons Ground control points (GCPs) can be used to evaluate the absolute accuracy of your point cloud. GCPs can be uploaded to LiDARMill as TXT or CSV files. Each GCP is designated either a check, control, or unused point. Only GCPs designated as control points will be used to adjust the point cloud vertically. In the **GCPs** tab, click the red plus button to "Create new reference station artifact". ![](/files/-MT5DoejcIvfI8g185le) --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.phoenixlidar.com/lidarmill-cloud/workflow/adding-ground-control-points-and-polygons.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.