Some of the things we’ve found make the most significant difference are: To improve the resolution of our topographic mapping, we randomly distribute Ground Control Points throughout the dataset. In short, Ground Control Points are essential to provide project accuracy and Check Points are used for verifying that your data and your solution is indeed correct. Check Points, which as a Best Practice are taken along with GCPs, are not used to adjust the project, but are used as an independent accuracy check. In a nutshell, the way that GCPs work is that these fixed points in the project are used to physically adjust the project in 3 dimensions to align it with the GCPs, and therefore create both global and local accuracy. What you see is the visual difference in a project with and without Ground Control Points. This may not sound too bad, but a small 1,000 foot project being off one percent could create a 10 foot error! By using Ground Control Points with proper gathering and processing procedures, You will typically be able to create projects with 1/10 th of a foot (2-3cm) accuracy.Ī real world example of how Ground Control Points will significantly improve your results is below. Provide 3 dimensional measurements that you sell your clientĬan you accurately topographically map a site without GCP? Without either GCP or an RTK aircraft, a project could easily be off 1%.Accurately scale the project in all three axes.Correctly geolocate the site being surveyed.This will increase your accuracy in the X-Y and Z axes, (also commonly known as X,Y,Z Northing, Easting, Elevation and Latitude, Longitude and Altitude). They are physically marked locations with a fixed position and their coordinates have been precisely determined. Why use Ground Control Points? In a word – accuracy. (Another method, Real Time Kinematics (RTK), requires a specially equipped drone and a ground reference base station, and will be the subject of a future blog article). So, how do you obtain the highest amount of accuracy in your drone mapping project? The most common method is to use Ground Control Points. However, if you are doing UAV mapping, being “close enough” is a waste of your time and your clients’ money. Close enough is great if you are playing horseshoes or tossing hand grenades. As my surveyor partner indicates, “If you don’t have an accurate project, it’s nothing more than a pretty picture…”. In the business of UAV mapping, accuracy is everything.