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Format
Data
ALOS 1 data is available through ASF Vertex
ALOS 2
Level 2.2 ScanSAR is available on Google Earth Engine (account needed)
ScanSAR that is “freely available” is described here as being available only through Google Earth Engine and the JAXA G-Portal, which links to the download site that refuses to load, so as of now, Earth Engine is the only option. Explanation of the situation here.
Issues
Common documented issues:
ALOS Orthorectification (seems solved, https://forum.step.esa.int/t/alos1-geocoding-and-terrain-correction-problem-in-s1/1488 ). Often talks about products being terrain corrected to the wrong spot
Terrain Correction on level 1.5 ALOS 2 products (potential solution) Level 1.5 data is geocoded but not georeferenced and SNAP run into problems with this, so the solution is SAR mosaic with just one file. Geocoding seems to be inaccurate in some cases (ALOS2 data downloaded from JAXA, rather than ASF). Other report of problems with geocoding of L1.5
NullPointerException when importing https://forum.step.esa.int/t/alos-2-l1-5-geotiff-not-opening/30147 https://forum.step.esa.int/t/error-import-alos-2/35671 https://forum.step.esa.int/t/import-alos-2-ceos/48 (comment describing workaround)
Problems creating interferograms with ALOS data, potentially caused by issues with coregistration. Report of problems with coregistration. More problems
ALOS2 data seems to generally fail to line up properly with other products, at least sometimes
There is a difference between data downloaded from ASF Vertex and data downloaded directly from JAXA. Data from ESA matches one but I am unsure which, and I don’t exactly know what the difference is. (Example, ALOS1 downloaded from ASF works with ellipsoid correction, but from ESA it fails)
https://forum.step.esa.int/t/support-for-terrain-correction-of-alos-and-alos-2-level-1-1/1186
Some issues for which the solution or group they belong to is unclear
https://forum.step.esa.int/t/alos-palsar-interfarogram/871/3
https://forum.step.esa.int/t/terrain-correction-of-alos-2/2941/2
https://forum.step.esa.int/t/alos-palsar-ceos-data-processing-in-snap/9884
https://forum.step.esa.int/t/alos-palsar-2-scansar-level-1-5g-metadata-edit/29904
https://forum.step.esa.int/t/problem-with-using-alos-data/10186/4 (problems with ramps on interferograms)
https://forum.step.esa.int/t/alos-palsar-2-scansar-level-1-5g-metadata-edit/29904
https://forum.step.esa.int/t/coregistration-error-of-alos-2-images/17693
Current ALOS tutorials
http://step.esa.int/docs/tutorials/ALOS PALSAR Orthorectification Tutorial.pdf
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