Direct Georeferencing In Unmanned Aerial Vehicle Using Quasi-Zenith Satelite System

To produce accurate topographic data, Unmanned Aerial Vehicle (UAV) still rely on Ground Control
Points (GCPs) for georeferencing. However, using GCPs has several limitations, among others, related
to the cost and time required for field measurements. In addition, not all areas are accessible for GCPs
measurements due to poorly accessible terrain or security reasons. Direct georeferencing, a method to
determine precise camera position and orientation in UAVs using Global Navigation Satellite System
(GNSS) geodetic antenna. Post Processing Kinematic (PPK) or real-time coordinates can be applied to
determine the camera position. One satellite that sends corrections to the rover on Earth is the Quasi-
Zenith Satellite System (QZSS). This study aims to analyze the orthophoto accuracy of the results of
direct georeferencing using precise coordinates from the QZSS satellites. The flight parameter was
used at 60% sidelap and 80% overlap on an average flying altitude of 300 m above ground level
resulting in 135 photos with a Ground Sampling Distance (GSD) value of 6 cm. The accuracy of direct
georeferencing using QZSS horizontally and vertically was 1.134 m and 1.617 m, respectively.
Meanwhile, the same metric results using conventional GCPs were 0.417 m horizontally and 0.419 m
vertically. With these results, the horizontal accuracy of Direct Georeferencing using corrections from
QZSS can be used for large-scale mapping of the 1: 5,000 class 1 scale, while vertical accuracy can be
used for large-scale mapping of the 1: 5,000 class 3 scale. Direct georeferencing using QZSS
corrections has the potential to support the acceleration of large-scale mapping activities in Indonesia.