Gamma LAT: Reference Manual

histogram

ANSI-C programs: histogram.c

NAME
histogram - Calculates histogram of test-area values (polygon regions).

SYNOPSIS
histogram <data_in> <width> <polygon> <histograms> <mean/stdev> <start> <stop> [lin/log_flag]

<data_in>	input data file (float)
<width>	number of samples/row
<polygon>	polygon data file
<histograms>	calculated histograms (output)
<mean/stdev>	calculated mean/stdev (output)
<start>	start value for first histogram class
<stop>	stop value for last histogram class
[lin/log_flag]	flag to select lin or log scale for output (default=0: linear scale; 1: values in dB)

EXAMPLES
histogram 1352_1610.cc_ad 2500 1352_1610.poly 1352_1610.cc_ad.hist 1352_1610.cc_ad.dat 0.0 1.0 0

Extracts coherence values and writes histograms, mean and stdev (absolute values) of each polygon region to output file.histogram 1352_1610.pow1 2500 1352_1610.poly 1352_1610.pow1.hist 1352_1610.cc_ad.dat -25.0 -5.0 1Extracts backscatter values, converts it to dB scale and writes histograms, mean and stdev (absolute values) of each polygon region to output file. 50 histogram classes between -25 and -5 dB are used.

INSTALLATION
Source code histogram.c in ./src. For compilation adjust and use Makefile: Executable version histogram in ../bin

AVAILABILITY
Uses type definition file typedef_ISP.h.

DESCRIPTION
histogram extracts signatures for test areas defined by polygons. For each polygon region the histogram, mean, and standard deviation is calculated and written to the corresponding output files.

The range between the selected minimum and maximum values is divided into 50 intervals of equal length.

The program determines how many times values in a certain ointerval are found for a certain polygon region. The result is normalized with the total number of pixels, i.e. the sum of all the histogram values for a certain polygon is 1.0

If a logarithmic (i.e. dB) scale is selected, the image values are first converted to dB. The interval limits are also indicated in dB. The use of the logarithmic scale is mainly used for backscatter intensities and parameters derived from backscatter intensities.

The selection of the polygon regions is supported with the program polyras.

OPTIONS
The output histogram, mean and standard deviations are written to textfiles and may therefore easily be imported, displayed and printed by most commercial plotting software.

SEE ALSO
typedef_ISP.h, polyras, histogram_ras .

DIAGNOSTICS
All messages are generally self-explanatory.

NOTES
none.