ERS-1/2 Synthetic Aperture Radar (SAR) Precision Image ProductEntry ID: ERS.SAR.PRI
Abstract: The AMI combines two separate functions: the SAR and
the Wind Scatterometer. The SAR can operate in two modes:
Image Mode and Wave Mode. This product is produced from
data collected by the SAR in Image Mode. It is supplied as
images or 'frames' in a digital format and in photographic
SAR in Image Mode obtains strips of high-resolution
... imagery 100 km in width to the right of the satellite
track. On-ground signal processing is used to
build up an image from the backscattered energy, which
depends primarily on the roughness and dielectric
properties of the illuminated area.
The power demands during the Image Mode are such that
operating time has to be limited to a maximum of 12 minutes
during each orbit of which 4 in eclipse. The data rate of
100 Mbits/s is far too high for onboard storage, so images
can only be acquired within the reception zone of a
suitably equipped ground station.
A major advantage over optical sensors is the
capability of microwaves to penetrate clouds, therefore
providing all-weather imagery.
The Precision Image is a multi-look
(speckle-reduced), ground range image. It
is the product applicable for most users interested in
remote sensing applications. The product is calibrated and
corrected for the SAR antenna pattern and range-spreading
loss: radar backscatter can be derived from the product for
geophysical modelling, but no correction is applied for
terrain-induced radiometric effects. The image is not
geocoded, and terrain distortion (foreshortening and
layover) has not been removed.
Numbering sequence is relative to the satellite position, and so a
different position for the Ascending and Descending scenes.
Pixel size: (range-across track) 12.5 m;
(azimuth-across track) 12.5 m
Scene area: (range-across track) 100 km;
(azimuth-along track) at least 102.5 km
Scene size: (range-pixels) 8000 pixels per line;
(azimuth-lines) at least 8200 lines
Pixel depth: 16 bits (unsigned integer)
Product location accuracy: (range) 100 m; (azimuth)
Total product volume: ~ 131 Mbytes
Annotation in image: lat./long. of scene centre and
the four corners
Number of looks: 3
To order data please see
Start Date: 1991-07-30
Latitude Resolution: 12.5 m
Longitude Resolution: 12.5 m
ISO Topic Category
Quality These are 3-looks Precision Images, suitable for
Information is available through the ERS Help Desk in
properly calibrate these products.
With the implementation of the VMP 6 processor (July 1996) in
and Archiving Facilities (PAFs), ... configuration
ensure that products are generated using the same
parameters and present the same characteristics.
These products pass systematically an automatic quality control,
including visual inspections, in order to prevent the distribution of
products not corresponding to user requests, or mislocated respect to
the expected position.
Samples of products are analysed in depth in order to
ensure the full
compliance with specifications.
Samples of products over calibration sites are
analysed in order to
ensure the calibration accuracy of these products.
Data Set Progress
Distribution Media: CD-ROM
Role: DIF AUTHOR
Phone: +39 06 94180777
Fax: +39 06 94180292
Email: eohelp at esa.int
ESA/ESRIN Via G. Galilei
Postal Code: 00044
Creation and Review Dates
Last DIF Revision Date: 2008-08-14