Gamma DIFF&GEO: Reference Manual

map_section

NAME
map_section - Generate the DEM parameter file of a specified region and optionally extract this region from a geocoding lookup table. The program also can calculate the bounding box in range-doppler coordinates that covers the specified region. The lookup table values can be offset to represent the bounding region.

SYNOPSIS
usage: map_section <DEM_par> <n1> <e1> <n2> <e2> <post_north> <post_east> <DEM_par2> [lt] [MLI_par] [cflg] [lt2] [MLI_coord]

<DEM_par>	(input) DEM parameter file describing the map projection and geometry of the input lookup table
<n1>	northing map coordinate of the upper-left corner of the map segment (enter - for value in DEM_par)
<e1>	easting map coordinate of the upper-left corner of the map segment (enter - for value in DEM_par)
<n2>	northing map coordinate of the lower-right corner of the map segment (enter - for value in DEM_par)
<e2>	easting map coordinate of the lower-right corner of the map segment (enter - for value in DEM_par) NOTE: units for the corner coordinates depend on the projection specified in the DEM_par
<post_north>	posting of the output lookup table for map samples in northing (enter - to keep the posting in the DEM_par) NOTE: post_north must be a negative number to prevent the DEM from flipping north/south when displayed
<post_east>	posting of the output lookup table in map coordinates in easting (enter - to keep the posting in the DEM_par) NOTE: post_east must be a positive number to prevent the DEM from flipping east/west when displayed\
<DEM_par2>	(output) DEM parameter file describing the geometry of the output lookup table
[lt]	(input) lookup table for the transformation from map geometry to radar Range-Doppler Coordinates (RDC) (enter - for none) NOTE: The lookup table has the dimensions described by the input DEM_par
[MLI_par1]	(input) MLI image parameter file with the geometry used for the lookup table values (enter - for none)
[MLI_par2]	(input) MLI image parameter file with the geometry for the image that will be terrain geocoded (enter - to be the same as MLI_par1)
[cflg]	lookup table coordinate shift flag (enter - for default) 0: do not subtract range and azimuth offsets from the lookup table values (default) 1: subtract range and azimuth offsets from the lookup table values
[lt2]	(output) lookup table segment with the specified posting: post_north and post_east (enter - for none)
[MLI_coord]	(output) Rectangular region specified in MLI and SLC coordinates covering the region of the lookup table (text format) range_offset range samples azimuth_offset azimuth_lines

EXAMPLES

map_section geo/wise.dem_par 40.28 -107.84 40.21 -107.78 -8.e-5 8.e-5 streeter.dem_par geo/wise_1.map_to_rdc rmli_1_3/20100102_HH.rmli.par - 0 streeter_0.map_to_rdc streeter.offsets

Calculates a new DEM parameter file based on the input DEM par and the rectangular region defined by the parameters n1, e1, n2, and e2. The map samples spacing is defined by the post_north and post east parameters. These are set her to -8.e-5 and 8.e-5 respectively. The optional lookup table wise_1.map_to_rdc is resampled to match the specified region and posting. An MLI parameter file is provided to permit bounds checking of the lookup table values. In the where case (cflg : 0), no offset is applied to the lookup table values. The input lookup table values are interpolated to match the values of north/lat and east/lon posting provided on the command line

map_section
  geo/wise.dem_par 40.28 -107.84 40.21 -107.78 -8.e-5 8.e-5
  streeter.dem_par geo/wise_1.map_to_rdc
  rmli_1_3/20100102_HH.rmli.par - 1 streeter_0.map_to_rdc
  streeter.offsets

In this second example, cflg has been set to 1 so that offsets are applied to the lookup table. This means that the input data in range-doppler coordinates must be extracted to match the RDC bounding box calculated from the MLI_par1 parameters and the lookup table values. To use the resampled lookup table, the MLI image section must be extracted using the offset and size parameters printed to the screen and output in the offsets file.

map_section geo_30/ca.dem_par - - - - -12.5
  12.5 geo_30_12_5/ca.dem_par geo_30/ca_1.map_to_rdc
  mli_4_10/20070221.mli.par mli_2_5/20070221.mli.par 0
  geo_30_12_5/ca.map_to_rdc geo_30_12_5/MLI_coord

In this example the input lookup table at 30m posting is resampled to 12.5 meter posting. The input lookup table contains coordinates referring to positions in the slant range image with 4 range-looks and 10 azimuth looks while the output lookup table contains coordinates referring to positions in an MLI image with 2 range looks and 5 azimuth looks. In this way calculation for the lookup-table and geocoding refinement can be performed at 30 meters while the output products are resampled from higher resolution images to 12.5 meters.

DESCRIPTION

map_section is a program that supports selection of a region of a data set in map geometry such as a DEM or lookup table. The bounding box in map coordinates is specified by the upper right and lower left map coordinates. A new DEM parameter file is calculated using the corner coordinates and the north and east posting values. The units for the posting depend on the map projection being either degrees for geographic coordinates (EQA) or meters of the standard map projections or the radar specific SCH map coordinate system.

If the user enters an existing lookup table in the geometry described by the input lookup table. The values in the input lookup table will be resampled to cover the region specified in the new DEM parameter file with the specified posting. Bi-cubic spline interpolation is used to resample the lookup table values if this is required.

The user also has the option to provide a second MLI parameter file to define the geometry of the data that will be resampled in Range-Doppler coordinates. The bounding box of the data covered in the map projection is calculated in Range Doppler coordinates. This permits extraction of a section of the radar data to match the associated region in the map geometry. The bounding box in range doppler coordinates can be written to a text file. These corner coordinates can then be used to extract the associated region for the data in radar geometry. A new program cpd makes it easier to extract a region from fcomplex or float images that do not have an associated MLI parameter file.