C-band has lower coherence than L-band because of the vegetative decorrelation. L-band radar receives a reflected wave from the ground and is coherent even in a forest area. In contrast, an L-band radar with a long wavelength as found on ALOS, can penetrate vegetation. This means that DEMs derived from C-band don’t actually measure the earth’s surface, rather they show the top of the canopy. On the downside, C-band doesn’t penetrate vegetation. Tradeoffs of DEMs created with Sentinel’s C-Band The critical baseline for S1A is about 5 KM. Image alignment is problematic if the perpendicular baseline between images is greater than about 3/4 of the critical baseline because the images will be baseline decorrelated. However, as the baseline increases, the coherence decreases. So, from that perspective larger baselines are better than smaller. Interferogram sensitivity to the perpendicular baseline is such that a large baseline improves the InSAR’s sensitivity to height variations. The longer the time between images the higher the decorrelation.īaseline cannot be ignored. This not only minimizes the coherence loss, it also minimizes any potential ground motion. You need to pick a pair that has the least temporal baseline possible. Images with different flight directions (ascending vs descending) cannot serve as pairs for interferometry.Ĭoherence is key. Pairs must be of the same path number and must cover the same area. The optimum pair for DEM creation would have a large perpendicular baseline and a small temporal baseline. The baseline tool can be accessed as a stand-alone tool, or via a Vertex search. The user first creates an interferogram, and completes the appropriate phase unwrapping steps, then creates the DEM.ĪSF’s baseline tool may be used to select a pair of Sentinel images to create the DEM. This recipe allows the user to create a Digital Elevation Model (DEM) product from two Sentinel-1 SLC scenes. Radarsat Antarctic Mapping Project (RAMP).Global Ice Sheet Mapping Orbiter (GISMO).ALOS PALSAR – Radiometric Terrain Correction.ALOS AVNIR-2 Ortho Rectified Image Product.Soil Moisture Active Passive (SMAP) Mission.RADARSAT-1 and JERS-1 Restricted Data Acess.