GNSS accuracy analysis for Efficiency of ground control point (GCP) measurement

Nowadays, the Global Navigation Satellite System (GNSS) has a significant role in the field of surveying and mapping, especially in determining the coordinates of ground control points for rectifying aerial photography, satellite imagery and airborne lidar. Each of these rectification processes requires a different coordinate accuracy from 5 to 20 cm. This research will conduct GNSS measurement with radial method and observation length to see how far the required accuracy will be fulfilled. This research examined ten Ground Control Points (GCPs) using the GNSS receiver in Surabaya. Each GCP was observed for 2 hours with 15" epoch and then they were processed with an interval of 15 minutes such as 15', 30', 45', 60', 75', 90', 105' and 120' with the radial method. In general, the results showed that the longer the GNSS observation the more accurate coordinates from 0.923 m (15 minutes) to 0.011 m (120 minutes) will be achieved. Measurement of GCPs for aerial photogrammetry, High-Resolution Satellite Image (HRSI), and airborne LIDAR needs 15' observation both of radial and network method for less than or equal 10 km of baseline. For 10-20 km, the radial method needs 90' observation for photogrammetry, 75' observation for HRSI, 45' GCPs observation of airborne LIDAR, but for network methods need 45' observation for photo and HRSI and 30' observation for Airborne LIDAR.