RTK vs. PPK

• Traditionally, Ground Control Points or GCPs have been part of drone mapping and are used to create accurate maps. However, laying them out in the field requires additional time and preparation and could be challenging in inaccessible and unsafe sites.
• Real-time Kinematics (RTK) and Post-Processing Kinematics (PPK) are both methods/techniques used in drone mapping to determine precise locations of points on the ground. It involves the use of a Global Navigation Satellite System and the application of GPS corrections to enhance positioning accuracy without the need to set up GCPs. 
• In this article, you will learn how RTK and PPK work and how accuracy is achieved using each method.

Real-time Kinematics (RTK)

• RTK drones collect images and geotag them during flight. The geotags contain GPS information that may have positional errors since signals from satellites are refracted while traveling through the Earth's atmosphere, introducing measurement errors.
• GPS corrections are applied in real time. The corrections are provided by a fixed reference station also known as the base station. The base station is located at a known position which is acquired using another surveying technique. The corrections come from the base station and are transmitted to the drone, enhancing the measurements and accuracy of the recorded image positions.
• RTK rovers require a real-time connection to the base station when performing RTK drone surveys. In challenging environments, the connection between the rover and the base could be disrupted. There could be signal loss due to obstructions present in the surroundings. 

Post-processed Kinematics (PPK)

• In PPK, unlike the RTK, real-time connection with the base and rover is not required. The coordinates of the images are collected without any corrections applied or calculations made which means they are raw. 
• After the survey, the observations are processed using specialized software for calculating errors and determining necessary corrections to arrive on accurate data.
  
  
• For challenging environments, it is highly recommended to use the PPK workflow.