New Data Conversion Tool Simplifies Data Projection

by Britton Kerin, ASF User Tools Development

ASF announces the availability of a new GUI (graphical user interface) that guides the user through the process of ingesting, geocoding and exporting ASF SAR data products; translating them into a variety of formats.

ASF distributes most of its data in the Committee for Earth Observing Systems (CEOS) standard format. Although this format represents a serious effort to completely characterize the data available from remote sensing platforms, it is difficult for many users to handle.

Most commercial GIS and image processing applications provide minimal support for CEOS formatted data, and CEOS is complicated enough that writing programs to interpret it can be challenging. To use a Level-1 image, you must usually resample it into a common coordinate system, or map projection, and translate it to a form understood by other applications. The convert tool can do this.

The tool can ingest ASF CEOS data and interpret image samples in the usual methods: sigma, beta, or gamma normalized values, or amplitude or power. The image can then be geocoded (i.e., map projected) into one of the following common formats: universal transverse Mercator (UTM), polar stereographic, Albers conical equal area or Lambert azimuthal equal area. We can easily add other projections, if users have other specific needs.

Users can set an average height for their image within the GUI of the conversion tool to improve geolocation accuracy. The interpolation method used to resample the image is also adjustable. The resulting geocoded image can then be exported from the GUI in JPEG, PPM, TIFF or GeoTIFF format as either a byte or floating point image.

The GUI also supports batch processing of multiple images, so most users will not need to write scripts. However, a command line interface to the tool is available. The ASF User Tools Development group is currently developing geometric terrain correction from reference digital elevation models. This
technique will remove geolocation errors that are a normal result of variable terrain height in SAR imagery.

ASF user tool developers are also interested in supporting any particular user input and output format requirements. In general, the more a given format improves the usability of ASF data, the more interested we are in supporting that format.

A user forum dedicated to the ASF tools can be found at https://forum.asf.alaska.edu/.

To download the tools go to the URL at https://www.asf.alaska.edu/software/

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