Abstract
Geometric correction of SAR satellite imagery is the process to adjust the model parameters that define the relationship between ground and image coordinates. To achieve sub-pixel geolocation accuracy, the adoption of the appropriate geometric correction model and parameters is important. Until now, various geometric correction models have been developed and applied. However, it is still difficult for general users to adopt a suitable geometric correction models having sufficient precision. In this regard, this paper evaluated the orbit-based and time-offset-based models with an error simulation. To evaluate the geometric correction models, Radarsat-1 images that have large errors in satellite orbit information and TerraSAR-X images that have a reportedly high accuracy in satellite orbit and sensor information were utilized. For Radarsat-1 imagery, the geometric correction model based on the satellite position parameters has a better performance than the model based on time-offset parameters. In the case of the TerraSAR-X imagery, two geometric correction models had similar performance and could ensure sub-pixel geolocation accuracy.
Highlights
The Synthetic Aperture Radar (SAR) satellite system using a microwave signal to observe ground information can collect data over a large area under any weather conditions
Three TerraSAR-X images in SpotLight mode and two Radarsat-1 images in Fine Mode were used for the error simulation and the evaluation of the geometric correction models
Two geometric correction models to adjust the satellite position parameters and the time-offset parameters were evaluated using TerraSAR-X images of which a high accuracy of the satellite orbit and the sensor information have been reported in existing researches and Radarsat-1 images which have large errors in the satellite orbit information
Summary
The Synthetic Aperture Radar (SAR) satellite system using a microwave signal to observe ground information can collect data over a large area under any weather conditions. Sensor, and atmospheric condition information can ensure high geolocation accuracy of SAR images [10,25]. The geolocation accuracy might be different according to captured time and area due to geodynamic error sources like atmospheric signal delay [18,27] For this reason, GCP-based geometric correction techniques are still used as an alternative solution for a practical application. For a small satellite imagery, the polynomial geometric correction model that is based on an orbit model can reduce the correlated error sources such as the time delay in sensor, atmospheric delays, Earth movements, and errors in ephemeris information [17,21,22,23,29]. For verification of the precision of the suggested algorithms, TerraSAR-X images of which accuracy and stability of orbit and sensor information have been verified [10,14,19,25] and Radarsat-1 images that have the positional error of hundreds of meters in ephemeris information [20,30] were used
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