Spread the coverage across the survey area to increase accuracy. In a standalone rectangular flight areas generally 5 GCP sites are used. Typically, one point is placed near each corner of the survey area, with the fifth GCP fixed centrally.

Consider, GCP locations as vertex of a triangle. The area within the triangle will have the greatest accuracy as images are interrelated to more than one control. The area outside the triangle will decrease in accuracy as you move away from it as images become reliant on an adjacent processed image rather than the controls.

It is important that GCP be positioned on a site where they have minimal opportunity for disturbance, thereby increasing their longevity and reducing the necessity to replace them in the future.

Installing a semi-permanent GCP network for a site that is surveyed on a regular basis enables a “ready-to-fly” posture, avoiding the need to install or construct an extensive ground control network prior to each survey. Furthermore, utilising the same control locations not only saves preparation time prior to flying, but also improves comparative accuracy between different time-based models assisting in model merging and reconciliation.

Often is the case that we only want to survey what has changed within a larger area. When thinking about a GCP network design patterns of GCP to meet all you aerial surveying needs at different times and for different requirements.

For example, you might have a layout for stockpile areas and processing, another layout for the entire pit, another for the current active mining area and another that covers the entire site. These layouts can form subsets of a larger area and combinations of different points. Working in this way allows flights to be designed for stakeholder needs, yet they can still be merged with larger datasets to create combinations of other areas.

Attempt to locate GCP across the entire elevation range of the site being surveyed.

Placement of GCP should always consider their capture field of view. Ensure each GCP is observable from different directions. Control points which can be observed over a greater proportion of the captured data set will provide better opportunity to integrate control.

Avoid placing GCP next to higher objects that obscure their view. The more times that a GCP can be identified in different capture images then the better the meshing of information will be during data processing.