Hello Eddison,
I am not sure what source you are using for the ALOS PALSAR DEM that you are
describing. As far as I know, there is no systematically processed DEM made
from ALOS PALSAR data. There is a DEM composite that the Alaska Satellite
Facility (ASF) is using for their Radiometric Terrain Correction (RTC)
processing of the ALOS PALSAR that they have resampled from other sources. See
their web page for details:
https://asf.alaska.edu/data-sets/derived-data-sets/alos-palsar-rtc/alos-palsar-radiometric-terrain-correction/#dem_information
The web page explains that they were using the SRTM1 (1-arcsecond or about 30
m) DEM interpolated to the 12.5 meter spacing of the ALOS PALSAR RTC products.
The SRTM DEM has the EGM96 geoid reference. I think they may recently have
changed to using the Copernicus GLO-30 DEM that is also 1-arcsecond spacing but
uses the EGM2008 geoid reference. Again, they will interpolate it to the 12.5 m
spacing for their ALOS PALSAR RTC processing. Over the USA, they used the USGS
NED DEMs that are higher resolution.
If this is the source of the “ALOS PALSAR DEM” that you are using, you will be
better off getting the original DEM for your area from either the Copernicus
GLO-30 DEM sources (there are several) or the USGS NED DEM sources. You will
still have to do the geoid to ellipsoid height conversions but it won’t be
modified by the interpolation that ASF is doing in their RTC processing.
++Eric Fielding
JPL
Message: 1
Date: Mon, 2 Jan 2023 20:08:39 -0600
From: Eddison Araya <eddisonj...@gmail.com>
To: Nicolas Cadieux <njacadieux.git...@gmail.com>
Cc: qgis-user <qgis-user@lists.osgeo.org>
Subject: Re: [Qgis-user] Convert an ALOS PALSAR DEM from ellipsoidal
to geoid.
Message-ID:
<CAC-LqC=pqeiqoi4d7edh0t3jqtk8fepplwxkkyyr4ofldpn...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hello yes, thank you very much, according to that source it is EMG-2008
Regards!
eddison
[image: image.png]
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