# Setting and coordinating control points

> Source: https://topodrone.com/knowledge/topodrone-air2s-ppk-kit/setting-and-coordinating-control-points-SQW/
> Section: TOPODRONE Air2S PPK KIT
> Updated: 2026-10-02

To determine the accuracy of the final point cloud after data post processing, it is necessary to place control points (GCP – Ground Control Points) at the field work stage. Control points - well-defined on the point cloud relative to the relief and pre-coordinated with high-precision GNSS equipment. Check points are not involved in the processing and should not be confused with reference points. It is recommended to collect at least 3 control points in a section of one drone flight route.

> **Note:** To control the results of the aerial survey, it is recommended to coordinate the control points on any flat surface using GNSS measuring equipment such as a GNSS receiver mounted on a milestone using RTK or PPK methods.

> **Note:** Optimal surfaces for coordinating control points are roads, paths, paved areas and other such features that will be visible from different survey positions.

> **Note:** GCPs can be road marking elements, special folding identification signs or other self-contained signs.

> **Warning:** The coordinate system of control points should be the same as the base station phase center coordinate system and the project as a whole.

![Setting and coordinating control points](https://topodrone.com/knowledge/i/797496fb76d5a3e5.png)

A ground control point made with paint on the pavement is coordinated using the Reach RS2 GNSS receiver.

![Setting and coordinating control points](https://topodrone.com/knowledge/i/99d4385411686e19.png)

Ground control point of road markings, coordinated by the Reach RS2 GNSS receiver.

![Setting and coordinating control points](https://topodrone.com/knowledge/i/e6155519e74b3635.png)

The ground control point, made of a folding identification sign, is coordinated by the Reach RS2 GNSS receiver.