master [ parameter=value ... ] [ inputfile outputfile ]
Parameters are: projection, num_lines, num_samples, pixel_width, pixel_height, standard_lat, compute_angle, rotate_angle.
ronmaster generates a (master) dataset containing attributes that parameterize and earth transform. This transform relates line and sample coordinates to latitude and longitude coordinates for a user-defined geographical region. The center of this region is taken to be the center coordinates of the input dataset. The size of this region is specified via parameters num_lines, num_samples, pixel_width, and pixel_height.
ronmaster optionally tries to rotate the master dataset so it is parallel to the input dataset. For input datasets in satellite- sensor coordinates, this translates to making satellite subtrack run straight up and down in the output master dataset.
See master for a more complete description of how master files are used in TeraScan.
This is the map projection used to relate line/sample coordinates to latitude/longitude coordinates.
Valid responses are [ stereographic, rectangular, orthographic, polarstereo, equidist_azim, mercator, utm, polyconic, albers_conic, lambert_conic, lambert_azim. ] There is no default.
For minimal distortion, rectangular and mercator projections should not be used for maps centered near the poles.
This is the number of lines in the master dataset. Valid range is [>0]. There is no default value.
This is the number of samples in the master dataset. The valid range is [>0]. There is no default value.
This is the output pixel size (sample direction) at the center of the master dataset. The valid range is [>0 km]. The default is 0.01*(degree of latitude) = 1.1132km.
This is the output pixel size (line direction) at the center of the master dataset. The valid range is [>0 km]. The default is 0.01*(degree of latitude) = 1.1132km.
If projection=polarstereo, then standard_lat is the standard latitude of the polar stereographic projection, i.e. the latitude at which there is no distortion. This is a positive quantity that takes the direction of the center_lat.
For conic projections, standard_lat is the distance from the center to the standard parallels. For example, if center_lat = 40 N, and standard_lat = 5, then standard parallels are at 35 N and 45 N.
The valid range is [0 to 90]. The default is 70 for a polar stereographic projection. The default is 5 for conic projections.
If compute_angle is yes, rotate_angle is computed by ronmaster so the output master dataset is parallel to the input dataset. Otherwise, rotate_angle is user-specified.
Valid responses are yes and no. The default is yes.
This parameter allows the north end of the master dataset to be rotated clockwise through this angle. Normally, line 1 is the northern most line when rotate_angle is 0. This is not the case for polar stereographic projections centered away from the pole. See NOTES.
The valid range is [-180 to 180]. The default is 0.
The following example shows ronmaster being used to create different master datasets for the same input dataset. The input dataset is from an ascending noaa-7 pass, which as an orbital inclination of about 14 degrees after factoring the rotational rate of the earth.
% ronmaster n7.84191.23 M1 projection : char( 13) ? stereo num_lines : int ? 512 num_samples : int ? 640 pixel_width : real ? [1.1132] pixel_height : real ? [1.1132] compute_angle : char( 3) ? [yes] n7.84191.23: Computed angle of rotation = 14.2832 [214] % ronmaster n7.84191.23 M2 projection : char( 13) ? polarstereo num_lines : int ? 512 num_samples : int ? 640 pixel_width : real ? [1.1132] pixel_height : real ? [1.1132] standard_lat : real ? [70] 50 compute_angle : char( 3) ? [yes] n7.84191.23: Computed angle of rotation = -105.681
Polar stereographic projections centered away from the poles must be rotated so north is up. In the northern hemisphere, setting rotate_angle equal to center_lon will turn the master so north is up. (Note, west longitudes are negative.)
In the above example, the center longitude was approximately 119.96 w, so the net computed angle of rotation was 14.28 - 119.96 = -105.68.
In the southern hemisphere, setting rotate_angle equal to minus center_lon will turn the master so north is up.
Last Update: $Date: 2000/04/11 14:30:24 $