REPEAT PASS INTERFEROMETRY USING ALOS-2 PALSAR-2 DATA (STUDY CASE IN BRAZIL)

Abstract

We performed a process called SAR Interferometry (InSAR) to generate Digital Elevation Models (DEMs) from data pairs of the PALSAR-2 Synthetic Aperture Radar, from the ALOS-2 satellite. The pair of images used is a permutation between all acquired acquisitions of SAR data from ALOS-2, more precisely, we used data from two satellite passages (temporally spaced) in which the sensor was imaging the same area on the ground. There were PALSAR-2 L-Band Ultrafine images with an interval of 14 days between acquisitions (which is precisely the revisit time of the satellite) from two forest regions in the Paran´a state, Brazil. After the generation of the DEM, we observed a systematic error that generated a kind of very sharp ramp in the azimuthal direction. In this paper we present the followed steps and the investigation carried out to discover the causes of the error. We could observe that the satellite paths on the two dates suffer a relative displacement between them. In other words, this error occurs due to a non-constant baseline. This work was part of the R&D project of FAPESP (São Paulo State Research Support Foundation) entitled “Geração de inventários florestais a partir de um portfólio de soluções de sensoriamento remoto brasileiras de papel e celulose” (Generation of forest inventories from a portfolio of Brazilian remote sensing solutions for paper and cellulose) number “2017 / 25639- 5 - NRC - PIPE – Fase 2 Direta”.