Assessing the Performance of Different Direct-Georeferencing with Large Format Digital Cameras

Abstract

This paper provides an independent investigation into the quality, performance and reliability of the Direct Georeferencing (using in-flight control GPS and IMU systems to measure the exterior orientation parameters) with the new photogrammetric digital airborne camera systems, undertaken as a part of the German Society of Photogrammetry, Remote Sensing and Geoinfirmation (DGPF) investigation project for large format digital camera Z/I Imaging DMC and Z/I Imaging large format film camera RMC Top 15. This paper will present results from the imaging data flown at 6 different flight days over a test site in Germany during a 10 week time window starting in July till mid-September 2008. The two sensors were flown at two different flying heights, resulting in blocks with the same ground sampling distance (GSD); namely GSD = 8cm. The results of Direct Georeferencing from real trials using a traditional Zeiss RMK TOP 15 film frame camera and Z/I Imaging large format digital camera DMC will be presented. These cameras are fitted with an Applanix POS AV 510, GPS, IMU integrated system. In this paper, the quality of Direct Georeferencing for digital cameras and film cameras is assessed through the coordinates of independent measurement of check points. A traditional triangulation (AT) with ground control points will be performed to be used as a ‘benchmark result’ against which other results from direct georeferencing can be compared. The use of direct georeferencing by GPS/IMU can be distinguished in two different concepts: • The use of direct georeferencing (DG) to measure the exterior orientation parameters for photogrammetric data processing without using the aerial triangulation. • Direct georeferencing can be considered with aerial triangulation and the automatically measured minor control points (tie and pass points) and is called Integrated Sensor Orientation (ISO). Which approach is suitable for a specific task depends on many factors; e.g., the required accuracy and the image scale. In general, Direct Georeferencing without aerial triangulation (DG) is used for medium to small scale projects, while Direct Georeferencing with aerial triangulation (ISO) is applied to large and medium scales (Heipke et al., 2000). The results show the importance and the influence of GPS and IMU needed for Direct Georeferencing with these large format digital cameras, and how these cameras are sensitive to the accuracy of data form GPS and IMU sensors. These large format digital cameras can benefit from the higher quality of GPS and IMU data.