Hello @kestkat,
RTC products are not suitable for generating DEMs, as they do not include phase information.
The workflow for generating a DEM from SAR imagery compares the phase measurements from two acquisitions. You would need to start with two complex images (such as the ALOS PALSAR L1.1 products) acquired at different times over the same area, use SAR processing software to create an interferogram, then convert the results to a height file. NASA's Applied Remote Sensing Training Program (ARSET) has a nice presentation available that goes over the concepts of using SAR to generate DEMs and presents a workflow using ESA's SNAP software.
Unfortunately, ALOS PALSAR data is not particularly well-suited for generating a DEM. As described in the presentation linked above, the ideal SAR pair for creating a DEM would be acquired from two slightly offset places in space at as close to the same time as possible. ALOS had a repeat cycle of 46 days, and a lot of surface characteristics can change in that time, especially in areas with vegetation or strong seasonality. The most recent acquisitions were in 2011, so there may have been topographic changes since then. You must also evaluate the interferogram to determine if there are atmospheric impacts affecting the phase differencing calculations.
If you do use ALOS PALSAR to generate a DEM, make sure to check it against other DEM products (the Copernicus 30-m DEM is an excellent, freely available global resource) or benchmark datasets to make sure that it meets your requirements.
RTC products are not suitable for generating DEMs, as they do not include phase information.
The workflow for generating a DEM from SAR imagery compares the phase measurements from two acquisitions. You would need to start with two complex images (such as the ALOS PALSAR L1.1 products) acquired at different times over the same area, use SAR processing software to create an interferogram, then convert the results to a height file. NASA's Applied Remote Sensing Training Program (ARSET) has a nice presentation available that goes over the concepts of using SAR to generate DEMs and presents a workflow using ESA's SNAP software.
Unfortunately, ALOS PALSAR data is not particularly well-suited for generating a DEM. As described in the presentation linked above, the ideal SAR pair for creating a DEM would be acquired from two slightly offset places in space at as close to the same time as possible. ALOS had a repeat cycle of 46 days, and a lot of surface characteristics can change in that time, especially in areas with vegetation or strong seasonality. The most recent acquisitions were in 2011, so there may have been topographic changes since then. You must also evaluate the interferogram to determine if there are atmospheric impacts affecting the phase differencing calculations.
If you do use ALOS PALSAR to generate a DEM, make sure to check it against other DEM products (the Copernicus 30-m DEM is an excellent, freely available global resource) or benchmark datasets to make sure that it meets your requirements.
Statistics: Posted by ASF - hjkristenson — Tue Jun 25, 2024 12:48 pm America/New_York