dB Byte Product

annotated db-byte image - under construction

General Description/How can I use these data?

The dB Byte Product includes a separate byte (sometimes called "raw") image file for each polarization channel collected for a particular datatake. Which channels are included will depend upon the radar mode in which the data were collected. Each file starts with an ASCII-format VICAR label which contains information on how to display the image file.

Data Characteristics

The db-byte file created yields more than just a pretty picture. Each Data Number (DN) , i.e. byte pixel value, corresponds to a "sigma0" value. These DN's ranges from 0 to 255 or -127 to 128 , depending on whether or not it is interpreted with a sign bit or not . These DN's are mapped to sigma0 values between -40.2 dB to +10.8 dB (most natural targets will fall within this range). Sigma0 is a measure of the radar brightness of the target. Therefore, the db-byte images can be used for limited scientific analysis. However, each increment in DN will correspond to a 0.2 db increment in Sigma0, so users should be cautious of the quantization noise when doing any quantitative analysis. The db-byte software assumes that the data is calibrated. If the data is not calibrated, then an uncalibrated byte image of the amplitude will be created instead. This will be indicated during program execution and also within the vicar header of the file.

Because dB is a logarithmic scale, the db-byte images will be stretched in a log fashion. Some image processing programs can help stretch the data in other ways if desired (the log stretch is not optimum for display!). In order to convert the dB values to linear power ratio values, simply raise 10 to the power of one tenth the dB value.

These files are typically between 10 and 100 Mbytes.

Getting the Data

under construction

Reading the Data

A simple program, called dB Byte Read, is available to read the dB Byte files and convert individual pixel coordinates to db values.

Also, take a look at all the software choices .