llcontr2 [ parameter=value ... ] [ inputfile outputfile ]
Parameters are: master_file, z_variable, iso_values, sub_divs, num_arcs, text_height.
llcontr2 contours data that is provided on an evenly spaced grid. llcontr2 contours the data in the original coordinate system, and then transforms the resulting contours into master dataset line/sample coordinates. The resulting metafile can be overlaid on any image with the same earth location as the master dataset.
Input to llcontr2 must be a 2-D variable with an earth transform; i.e., latitude and longitude. Coordinates are computed rather than stored as separate variables. See llcontr for information on contouring data with other formats.
Normally, 2-D image variables are too large to contour directly. TeraScan functions subsamp, magnify, and nhood can be used to reduce the size of image variables prior to contouring.
One important operational note: If the grid is dense with respect to master_file, i.e., a very fine grid that has not been reduced using a function such as subsamp, the contours will be too close together to allow contour labels.
This is the filename of the master dataset. The earth location transform of the master dataset is used to convert latitude and longitude coordinates to line and sample coordinates during the metafile generation process.
Valid responses are any TeraScan dataset that contains an earth transform. The default is Master.
This is the name of the variable to be contoured. It must be a 2-D variable with an earth-transform. There is no default.
This is the list of levels to contour. No more than 30 levels can be contoured at once. If a single non-zero value is entered, the value is assumed to be the contouring interval and the iso_values are computed. To contour a single level, enter the value twice. If 0 is entered for iso_values, llcontr2 estimates the contour levels. The function performs this task by first selecting a contour interval of 1, 2, or 5 times a power of ten. Given this contour interval, the contour levels are estimated. Note: Lists of computed iso_values will not exceed 30 values.
For example, assume data with values between 1 and 10. 1 2 3 generates contours for the values 1, 2, and 3. 2 2 generates contours for the value 2. 2 generates contours for the integer values 2, 4, 6, 8, and 10. 0 generates contours of 1, 2, 3, 4 ..., 10.
Valid responses are [0, a number, or a vector of numbers]. The default is 0.
OPTIONAL. This is the number of contouring subdivisions per grid square. It must be a power of two. This parameter is used to prevent contours from overlapping.
Valid responses are [1, 2, 4, 8]. The default is 2.
OPTIONAL. This is the number of arcs in the contour segment that passes through a grid square. If 1 is used, straight lines are drawn through the grid squares. Larger values produce curved lines.
Valid responses are [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]. The default is 3.
OPTIONAL. This is the height of contour labels in units of master dataset pixels. Assuming that the master dataset is normally displayed at full resolution, a text height of 25 pixels results in ~1/4 inch text on a 16-inch graphics display.
The valid Range is [>= 1]. The default is 16.
Generate a TeraScan metafile dataset containing the contours of the 2-D dataset described in subsamp.
[1] % llcontr2 in/out files : char(75) ? big10 llcontr2.meta master_file : char(75) ? [Master] z_variable : char(15) ? avhrr_ch2 iso_values : real(30) ? [0] ? big10: processing a 120 X 141 grid
llcontr, subsamp, magnify, nhood
Last Update: $Date: 1998/05/29 18:35:02 $