Projected Local Incidence Angle

Last modified by Tuan Le on 2019/05/06 12:26

Projected Local Incidence Angle (PLIA) is the angle between the surface normal and the looking direction of the satellite or the Local Incidence Angle (LIA) projected into the range plane.

Product overview

The projected local incidence angle (PLIA) represents the angle between the surface normal and the looking direction of the satellite, which projected into the range plane. In short, the PLIA accounts for local slopes, which highly influenced by topography. Within the Austrian Data Cube project, the Sentinel-1 data are processed using the high-resolution digital elevation model (DEM), which theoretically enables the retrieval of the PLIA with the high resolution of 20m. The processing of PLIA product is carried out using the TU Wien SAR Geophysical Retrieval Toolbox (SGRT), which is the software for geophysical parameters retrieval from SAR imagery developed at TU Wien.

DEM influence on the PLIA product

Despite being less visible in the other products, the use of Austrian high-resolution DEM has a great influence on the actual resolution of the PLIA. The terrain is now visible in PLIA at the highest possible resolution (20m). The figure below compares different PLIA products over the same area, which generated using different DEMs with different resolutions.

Sentinel-1 PLIA over western Innsbruck, Austria, taken on 21st April 2016, 5:26:30 processed with SRTM 90m DEM (left) and the Austrian high-resolution DEM (right).

Product description

Generally, one PLIA image slice will be retrieved after the processing of one Sentinel-1 input file. Theoretically, the difference between two PLIA of the same orbit track is small and therefore, can be neglected. However, within this project, we provide one PLIA image for every pre-processed timestamp. In the following sub-section, the detail product format and important characteristics will be presented.

Product variables

The following table presents the overview of the format of the projected local incidence angle product after the processing at TU Wien.

Code nameScaling factorUnitsTypePixel size (m)Image dimensionNo-dataNumber of bands
PLIA100Degreeint1610,1010000x10000-99991

Overview of Sentinel-1 projected local incidence angle product variables

Area and time period

PLIA product is provided over the area of Austria from 01st January 2016 to the present.

Temporal resolution

As discussed above, the temporal resolution of PLIA product will be the same to pre-processed Sentinel-1 backscatter images, or 3-4 days over Austria in practical.

Image timestamps

The timestamps of PLIA product can be found in the filename, according to Sentinel file naming convention. It can also be found in the GeoTIFF header.

Spatial resolution and sampling

After the pre-processing at TU Wien, the PLIA images are tiled and georeferenced using the TU Wien Equi7(see Data specifications and formats) and have easting and northing coordinates with the pixel spacing of 10m.

Original data format

The PLIA data is originally stored and delivered in GeoTIFF format. GeoTIFF is a standard which allows storing georeferencing information within a TIFF raster image.

Sentinel-1 Projected Local Incidence Angle product at 10m spatial sampling. The scene covers the area of western Innsbruck, Austria, taken on 21st April 2016, 5:26:30.

Product NameProjected Local Incidence Angle
Code NamePLIA
CategorySentinel-1 products
Spatial Sampling10m
Temporal Resolution3-4 days
UnitDegree

Contents