I am doing a project with Landsat which needs to find out 2 Landsat images of the same area for different time, have both the same observation zenith and azimuth angles. But I can not find any information about satellite observation zenith or azimuth angle of Landsat images. Any one has an idea where I can find that information?
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do you have a _MTL.txt file with your data ?– radouxjuCommented Mar 27, 2014 at 6:59
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yes i have, but it only provide Sun elevation and Sun azimuth, but what i need is the observation angle of satellite. Example here 1drv.ms/1gEzZRn– Hung LuuCommented Mar 27, 2014 at 7:17
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I think that it is always nadir with Landsat. But I'm not 100 % sure.– radouxjuCommented Mar 27, 2014 at 7:21
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1 Answer
Satellite zenith angle
Images from Landsat 1 - 7 are always nadir.
In other words, their satellite zenith angle is close to 0°.
Likewise, the _MTL.txt you posted corresponds to a Landsat 5 image, and so is a nadir image.
Off-Nadir imagery has been introduced with Landsat 8.
Landsat 8 images have a field NADIR_OFFNADIR in their _MTL.txt metadata. The ROLL_ANGLE field indicates the corresponding satellite zenith angle. (See the Landsat Data Dictionary for a brief explanation of each metadata field.)
A typical nadir Landsat-8 OLI/TIRS scene would have metadata like:
NADIR_OFFNADIR = "NADIR"
ROLL_ANGLE = -0.001
Satellite Azimuth
I am not aware of a metadata field for satellite azimuth. You could either use the CORNER_ X / Y coordinates (or latitude / longitude respectively) (inside the _MTL.txt file) to calculate its azimuth.
Alternatively, you could utilize the WRS (Worldwide Reference System) information (metadata fields WRS_PATH and WRS_ROW; for landsat 4 onwards, it is sort of a grid indicating where the satellite is on its orbit). Have a look at the USGS page with has WRS specification documents and shapefile downloads, it is basically straightforward.
However, if you are comparing scenes from the same area, the satellite's azimuth angle is not subject to any change.
(Note that Landsat Metadata has changed a little bit as of August 2012.)
