The accuracy of drone mapping is largely dependent on the sampling distance of the terrain (GSD, that is, the number of pixels per centimeter) of the data. To assess the vertical accuracy of the drone results, a common practice is to compare them with RTK GPS checkpoints. The RTK GPS is highly reliable and has an accuracy of approximately 2.5 cm (1″). The RMS error is the final calculation of the accuracy of the drone cartographic surveys when all possible sources of error in the model (not just the GSD or GPS error) have been taken into account.
Ground Control Points (GCPs) are defined and measured points on the natural surface that are used to amplify precision and unite the images captured by the drone. One of the most important aspects of drone topography is spatial data or ground sampling distance (GSD), as defined in terms of photogrammetry. In recent years, drones have revolutionized how construction and earthmoving companies analyze and manage their worksites by providing accurate and reliable topographic data. There are two types of precision when it comes to drone cartographic studies (or any other type of survey): relative precision (also known as local precision) and absolute precision (also known as global precision).
This should also apply to drone topography and photogrammetry, and the information that is processed and delivered about a project must indicate the methodology, assumptions, errors and general accuracy of the data being provided. The absolute accuracy of drone survey data is measured by comparing the observed coordinates (the positions of the control points in the model) with the authorized positions (the coordinates measured independently of the same points on the ground). The first element that must be taken into account to estimate the accuracy of drone survey data is the terrestrial sampling distance (GSD), a measure of the smallest object that would appear visible in the original photographs, before processing them in the cartographic outputs. It is still necessary to understand and combine topographic methodology, photogrammetry and geospatial software to process, validate and control the quality of the acquired drone data.
Drone maps created with good quality drone equipment, careful flight planning, GPS ground control points for commercial use and processing software for commercial use can be accurate to about 2-3 cm horizontally and about 5-6 cm vertically. The only established method for checking and demonstrating the accuracy of drone cartographic surveys is to use independently measured control points. The use of drones for mapping has become increasingly popular due to its cost-effectiveness, efficiency, and accuracy. With proper flight planning, GPS ground control points for commercial use, good quality drone equipment, and processing software for commercial use, it is possible to achieve an accuracy level of 2-3 cm horizontally and 5-6 cm vertically. This level of accuracy makes it possible for construction companies to analyze their worksites more accurately than ever before. In conclusion, it is important to understand both topographic methodology, photogrammetry, and geospatial software in order to process, validate, and control the quality of acquired drone data.
With proper understanding and implementation, it is possible to achieve an accuracy level that can be used for commercial purposes.