PPK (Post-Processing Kinematic) provides much higher accuracy in GPS location when stored against images taken in a UAV. Standard GPS signals are accurate to 10's of metres - PPK increases that accuracy to cm-levels. On board the Q-200 UAV, PPK eliminates the need for physical Ground Control Points (GCP) that are often used to gain high accuracy in surveys. This saves hours of mission planning and setup time, physically measuring location points and walking the survey site for placement.
Surveys involving GCP generally run like this:
In most cases - up to half of the mission time is taken up with GCP placement. GCP targets may shift or collapse with changing weather conditions – requiring the original placement to be repeated (often wasting up to an hour of survey setup time); coastal surveys can suffer from tidal changes and cliffs make it difficult to place GCPs across the survey area; general survey ground conditions can make it difficult to secure GCPs - quarries are a good example of difficult, variable ground surfaces.
The PPK solution offered by QuestUAV uses a higher performance, highly-accurate receiver placed within the aircraft - following more than 10 GPS satellites at any given time and storing location information against the triggered images taken. Combined with differential signal information collected by the fixed position Ground Station (which stores signal drift and signal error values), the image locations are recalculated to a much higher accuracy – down to centimetre level in x, y and z direction.
Compared to RTK (Real Time Kinematic), PPK also eliminates the need for a real-time data link with a fixed reference station during the flight, whilst guaranteeing RTK cm-level position accuracy of the images once post-processing has taken place, after the UAV lands. This simplifies the UAV set-up, reduces the requirements and power drain on-board and eliminates any loss of accuracy in data due to potentially unreliable radio links - which often plague RTK UAV operations.
The Q-200 Surveyor Pro is available with PPK at purchase or as an upgrade to an existing aircraft with the provision of just the PPK QPod.
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