Sentinel-1 local incidence angle and layover/shadow mask#

sentinel-1-local-incidence-angle · theme sar · live

The angle between the radar look vector and the terrain normal, with the layover and shadow mask: read from the OPERA RTC-S1-STATIC per-burst layers, or computed from any DEM with no account at all (issue #10). One raster per relative orbit; tracks are never fused.

import easysnowdata as esd

aoi = (-121.94, 46.72, -121.54, 46.99)   # Mount Rainier
local_incidence_angle_ds = esd.sar.sentinel1.local_incidence_angle(aoi, time="2024-03")

Credentials

The default route needs earthdata; see the credentials page for the setup.

An open alternative exists: source="dem".

Sources#

3 routes serve this product; the first is the default and source= picks another. The return contract is the same either way.

source	provider	credentials	resolution	extent	temporal	latency	notes
`opera-static` (default)	stac	earthdata	30 m	global	static, one granule per burst	—	ships local_incidence_angle, incidence_angle, mask (layover/shadow), number_of_looks, and the gamma0→beta0/sigma0 factors as COGs. ASF’s datapool refuses a bearer token alone (EARTHDATA_TOKEN); the reads need a netrc entry or EARTHDATA_USERNAME/EARTHDATA_PASSWORD
`dem`	stac	none	30 m	global	static (DEM epoch)	—	an approximation: processing.sar.local_incidence_angle on the Copernicus GLO-30 DEM, with the track’s heading and a linear across-swath incidence field read from a Planetary Computer RTC scene footprint; no credentials, no layover/shadow mask. For the exact geometry without OPERA, see github.com/egagli/generate_sentinel1_local_incidence_angle_maps
`gee`	gee	earthengine	30 m	global	2014-10/present	—	the S1_GRD angle band is the real per-pixel ellipsoidal incidence angle of the chosen track; the terrain part is the same DEM computation as source=’dem’

Where each route points#

opera-static — OPERA RTC-S1-STATIC (ASF) live: OPERA_L2_RTC-S1-STATIC_V1_1
dem — computed from the Copernicus DEM live: cop-dem-glo-30
gee — Earth Engine (S1_GRD angle band) live: COPERNICUS/S1_GRD angle band + COPERNICUS/DEM/GLO30

Variables#

variable	units	dtype	nodata	categorical
`local_incidence_angle`	degrees	float32	—	no
`incidence_angle`	degrees	float32	—	no
`mask`	—	uint8	255	yes (5 classes)

Provenance#

Licence · NASA Earthdata (free registration) / Copernicus DEM licence

Cite the data as

OPERA RTC-S1-STATIC, NASA/JPL, distributed by ASF DAAC; European Space Agency, Sinergise (2021), Copernicus Global Digital Elevation Model.

Documentation

Loader · easysnowdata.sar.sentinel1.local_incidence_angle

Gallery examples#

Sentinel-1 RTC backscatter and local incidence angle

value	meaning
0	not_layover_shadow_or_water
1	shadow
2	layover
3	layover_and_shadow
255	fill