FIX: Use the sun elevation angle rather than the sun zenith angle for…

… STAC #158
sertit · Dec 3, 2024 · 1549fb0 · 1549fb0
1 parent 8020c5b
commit 1549fb0
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Showing 3 changed files with 10 additions and 2 deletions.
diff --git a/CHANGES.md b/CHANGES.md
@@ -11,6 +11,7 @@
 - FIX: Add a fallback in case `map-overlay.kml` is not readable for `Sentinel-1` data ([#180](https://github.com/sertit/eoreader/discussions/180),[#182](https://github.com/sertit/eoreader/issues/182))
 - FIX: Remove warning about Dask's lock and client
 - FIX: Don't throw an error in case of missing cloud coverage, only a warning and set the cloud coverage to 0 [#159](https://github.com/sertit/eoreader/issues/159)
+- FIX: Use the sun elevation angle rather than the sun zenith angle for STAC [#158](https://github.com/sertit/eoreader/issues/158)
 - DOC: Update `conf.py` (remove useless hunks and set Sphinx 7 as base)
 - DOC: Added the [PAZ product guide](https://earth.esa.int/eogateway/documents/20142/37627/PAZ-Image-Products-Guide.pdf) to the PAZ Product documentation instead of the TerraSAR-X one - by @guillemc23
 

diff --git a/CI/SCRIPTS_WEEKLY/test_stac_creation.py b/CI/SCRIPTS_WEEKLY/test_stac_creation.py
@@ -258,7 +258,8 @@ def _test_core(
                     except KeyError:
                         pass
 
-                    sun_az, sun_el = prod.get_mean_sun_angles()
+                    sun_az, sun_zen = prod.get_mean_sun_angles()
+                    sun_el = 90 - sun_zen
                     compare(
                         item.properties[VIEW_SUN_AZIMUTH],
                         sun_az,
@@ -269,6 +270,7 @@ def _test_core(
                         sun_el,
                         f"{VIEW_SUN_ELEVATION} (item.properties)",
                     )
+                    assert -90 < sun_el < 90
 
                     azimuth, off_nadir, incidence_angle = prod.get_mean_viewing_angles()
                     if azimuth is not None:

diff --git a/eoreader/stac/stac_extensions.py b/eoreader/stac/stac_extensions.py
@@ -333,7 +333,12 @@ def __init__(self, prod, **kwargs):
             "incidence_angle": VIEW_INCIDENCE_ANGLE,
         }
         try:
-            sun_az, sun_el = prod.get_mean_sun_angles()
+            # This fct gives the sun zenith angle
+            sun_az, sun_zen = prod.get_mean_sun_angles()
+
+            # STAC wants the sun elevation angle
+            # https://en.wikipedia.org/wiki/Solar_zenith_angle#Formula
+            sun_el = 90 - sun_zen
 
             # Convert from numpy dtype (which are not JSON serializable) to standard dtype
             self.sun_az = stac_utils.to_float(sun_az)