Based on information in some references the resolution of ECOSTRESS was better originally than 70 meters.
"From the ISS, PHyTIR will provide data with 38-m in-track by 69-m cross-track spatial resolution" https://ecostress.jpl.nasa.gov/instrument
Why is this downsampled to 70 meters? was that increasing snr? can we access the highest resolution?
ECOSTRESS Highest resolution
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LP DAACx - lien
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Re: ECOSTRESS Highest resolution
Hello,
In any given Ecostress swath directly from the sensor on board the ISS the pixel size ranges from ~38 meters x 69 meters to ~90 meters x 90 meters along the edge of the swath. So pixel size varies greatly as it does with most all satellite data. The derived products need to be uniform so ~70 x 70 meters was deemed the best option. When the pixel is geolocated it is better for most to work with as a square. Following is from the User-Guide:
The TIR data is acquired at a spatial resolution of approximately 35m x 70m with a swath
width of approximately 400 km. The Level-1B Radiance product resamples the 5 TIR bands so they are
spatially co-registered, and averages in the line direction to produce roughly 70m x 70m pixels. The
Level-1B Geolocation product corrects the ISS reported ephemeris and attitude data by image matching
with a global ortho-base (based on Landsat data), and then using this improved navigation information
to assign latitude and longitude values to each of the Level-1 Radiance pixels. When image matching is
successful, the data is geolocated to better than 50-meter accuracy. In addition, related information
about solar and view geometry, surface height, and fraction of pixel on land vs. water are generated.
Please let me know if you have any questions.
Thanks,
Brett
In any given Ecostress swath directly from the sensor on board the ISS the pixel size ranges from ~38 meters x 69 meters to ~90 meters x 90 meters along the edge of the swath. So pixel size varies greatly as it does with most all satellite data. The derived products need to be uniform so ~70 x 70 meters was deemed the best option. When the pixel is geolocated it is better for most to work with as a square. Following is from the User-Guide:
The TIR data is acquired at a spatial resolution of approximately 35m x 70m with a swath
width of approximately 400 km. The Level-1B Radiance product resamples the 5 TIR bands so they are
spatially co-registered, and averages in the line direction to produce roughly 70m x 70m pixels. The
Level-1B Geolocation product corrects the ISS reported ephemeris and attitude data by image matching
with a global ortho-base (based on Landsat data), and then using this improved navigation information
to assign latitude and longitude values to each of the Level-1 Radiance pixels. When image matching is
successful, the data is geolocated to better than 50-meter accuracy. In addition, related information
about solar and view geometry, surface height, and fraction of pixel on land vs. water are generated.
Please let me know if you have any questions.
Thanks,
Brett
Re: ECOSTRESS Highest resolution
Thanks brett for the clarification. I understand how the resolution of ~68 cm could degrade to ~90 cm at the edge of the swath. This makes sense because of the across-track pixel distortion as we move further from nadir. However, I believe the same degree of degradation doesn’t apply to the 38 cm resolution along the track.
For polar-orbiting satellites (like ECOSTRESS), we don’t experience significant off-nadir effects in the along-track direction because the scanning is primarily in the across-track direction. For example for modis 1km*1km would get to 2km(along track resolution)*4.8km(across track resolution) and not 4.8*4.8.
(This is in contrast to geostationary satellites, which scan off-nadir in both directions, leading to more uniform degradation.)
So, while I agree that resolution worsens at the edge, based on my calculations, resolution at the extremes to be closer to ~45m× 90 m, rather than ~90 m× 90 m(I know it is what mentioned in the ECO1B-user guide). The average resolution of ~70 m (almost between 45 and 90 ) you mentioned seems to align well with this reasoning.
your comments about the above conclusion would be really appreciated.
For polar-orbiting satellites (like ECOSTRESS), we don’t experience significant off-nadir effects in the along-track direction because the scanning is primarily in the across-track direction. For example for modis 1km*1km would get to 2km(along track resolution)*4.8km(across track resolution) and not 4.8*4.8.
(This is in contrast to geostationary satellites, which scan off-nadir in both directions, leading to more uniform degradation.)
So, while I agree that resolution worsens at the edge, based on my calculations, resolution at the extremes to be closer to ~45m× 90 m, rather than ~90 m× 90 m(I know it is what mentioned in the ECO1B-user guide). The average resolution of ~70 m (almost between 45 and 90 ) you mentioned seems to align well with this reasoning.
your comments about the above conclusion would be really appreciated.
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LP DAACx - lien
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Re: ECOSTRESS Highest resolution
Good Morning,
The User Guide states 90 x 90, and I can't comment on that because I don't know their rationale or formula for arriving at that value, also, I don't know your formula for arriving at 45, but that does make it seem reasonable for the developers to arrive at ~70 meters, along with the fact it makes them square. Please bear in mind however that Ecostress is not a polar orbiting satellite but goes east to west on the Space Station.
Thanks,
Brett
The User Guide states 90 x 90, and I can't comment on that because I don't know their rationale or formula for arriving at that value, also, I don't know your formula for arriving at 45, but that does make it seem reasonable for the developers to arrive at ~70 meters, along with the fact it makes them square. Please bear in mind however that Ecostress is not a polar orbiting satellite but goes east to west on the Space Station.
Thanks,
Brett