Grid Programs

Bob Simpson - U.S. Geological Survey, Menlo Park, CA

This is a brief description of a number of programs for manipulating US Geological Survey Geophysics Branch Standard Grid files:

gclrx

Colors a grid in an X-window. Allows a metafile to be saved which can be converted to Postscript of Adobe Illustrator format.

gheader

Displays the header line information of a standard grid. Allow changes to be made in the header line.

glevel

Calculates the average value (level) of the grid, and prints the number of dvals (no data flags).

gprj

Projects a grid using various map projections. Because the data in the resulting projected grid will be tapered, the starting grid should be larger than the final area of interest, so that the margins can be trimmed.

gregrid

Allows a grid to be refined or coarsened by regriding using linear interpolation. If change in grid spacing is too great, can result in artifacts that show up with derivatives or shading.

greprj

Reprojects a projected grid using a new set of projection specs.

gsubgrid

Extracts subgrids from a grid.

gthin

Thins a grid by saving every n-th column and row. Useful for quick inspection of very large grids in gclrx.