A Comparison of GNSS Measurement Methods for Orthorectification of High-Resolution Satellite Images: A Case Study of Worldview-2 and Geoeye-1 Satellite Images in Padang City, West Sumatera, Indonesia

The selection of primary data sources for crucial mapping activities is based on the accuracy and precision of geospatial data, particularly those derived from remote sensing. High-resolution satellite imagery products need to be orthorectified as part of the geometric correction process to be suitable for producing large-scale base maps such as 1:5,000 scale maps used for spatial planning, boundary delineation, and detailed spatial planning. This technique mitigates the geometric distortions caused by satellite positioning hundreds of kilometers above the Earth's surface and other physical and technical challenges. This research aims to compare and determine the highest accuracy values for two GCP measurement methods, Radio RTK and RTK-NTRIP, in the orthorectification process of WorldView-2 and GeoEye-1 satellite imagery owned by Digital Globe of the United States. This type of imagery is prevalent in regions like Sumatra, where large-scale topographic maps are not readily available. The research process starts with the collection of raw WorldView-2 and GeoEye-1 imagery data and the National DEM covering the area of Padang City, followed by field measurements using Geodetic GPS with both offered methods to obtain coordinate values for both GCP and Independent Check Points (ICP). The comparison results should be analyzed according to the Head of Geospatial Information Agency (BIG) Regulation No. 6 of 2018 to classify the horizontal accuracy values using Toutin's 90% CE90 method. These two methods are expected to determine the differences in horizontal accuracy margin values, which can be recommended for orthorectification processes according to BIG standards.