<p>I tried to process the L2 NH3 data from IASI.
How can I estimate the elliptical footprint of a pixel from the following geolocation and geometry data for the IASI instrument?
The available information are the solar zenith angle at the Earth's surface for the pixel center, Metop zenith angle at the Earth's surface for the pixel center,  longitude and latitude of ground pixel center, and spatial resolution at nadir ~ 12 km.
I could not follow the AAPP software manual and could not install the software.
Online searching has not been very helpful either.
Thanks
Dong</p>

CC BY-SA 4.0
2024-10-15T07:31:31.730Z
I had this problem 15 years ago (for HIRS) and did not find a good solution.  It's complicated, as one should ideally consider not only the Instantaneous Field Of View (IFOV; basically the antenna pattern), but also the Effective Field Of View (EFOV), as the satellite moves during the integration time (and maybe the instrument too, depending on how it scans).  There is some [Matlab code for AMSU here](https://arts.mi.uni-hamburg.de/svn/rt/atmlab/trunk/sensors/calculate_footprint_size_amsu.m) that you might adapt for IASI.
gerrit
CC BY-SA 4.0
2024-10-15T09:43:34.303Z
Maybe pyorbital can help ([documentation](https://pyorbital.readthedocs.io/en/latest/), [GitHub page](https://github.com/pytroll/pyorbital)).
gerrit
<remote-sensing><satellites><gis><geospatial><geometry>
footprints L2 IASI data
Dong Liang
# footprints L2 IASI data

(Asked by: username_0 on 2024-10-14)

I tried to process the L2 NH3 data from IASI.
How can I estimate the elliptical footprint of a pixel from the following geolocation and geometry data for the IASI instrument?
The available information are the solar zenith angle at the Earth's surface for the pixel center, Metop zenith angle at the Earth's surface for the pixel center, longitude and latitude of ground pixel center, and spatial resolution at nadir ~ 12 km.
I could not follow the AAPP software manual and could not install the software.
Online searching has not been very helpful either.
Thanks
username_0

**Tags:** remote-sensing, satellites, gis, geospatial, geometry

> **Comments:**
> **username_1**: I had this problem 15 years ago (for HIRS) and did not find a good solution.  It's complicated, as one should ideally consider not only the Instantaneous Field Of View (IFOV; basically the antenna pattern), but also the Effective Field Of View (EFOV), as the satellite moves during the integration time (and maybe the instrument too, depending on how it scans).  There is some [Matlab code for AMSU here](https://arts.mi.uni-hamburg.de/svn/rt/atmlab/trunk/sensors/calculate_footprint_size_amsu.m) that you might adapt for IASI.  
> **username_1**: Maybe pyorbital can help ([documentation](https://pyorbital.readthedocs.io/en/latest/), [GitHub page](https://github.com/pytroll/pyorbital)).  

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## 0 answers

