Merge Grid Files

This command creates a grid file by merging together two existing grid files, grid1 and grid2. The current grid is grid1 and the program will prompt for a second grid. These two grids must overlap with the same location and resolution. The inclusion and exclusion perimeters apply to grid2 such that the merged grid will consist of grid2 cells within the inclusion perimeters and outside the exclusion perimeters and grid1 cells everywhere else. The result is stored in the current grid.

No elevations are calculated on grid cells that extend beyond the extent of the data. Extrapolation can be used to calculate elevations for the grid cells that are beyond the data limits. The prompt Extrapolate grid to full grid size? shows when there are grid cells with no elevation in a grid (.GRD) file. Extrapolation fills in all the grid cells. The method to extrapolate uses a safe calculation that tends to average out or level the extrapolated values. So extrapolated grid areas are not as accurate as grid areas within the limits of the data.

Prompts

Select Source Grid 1 File Dialog (file select dialog)
Reading cell> 93058
Extrapolate grid to full grid size [Yes/<No>]? press Enter
Select Source Grid 2 File Dialog (file select dialog)
Reading cell> 62137
Extrapolate grid to full grid size [Yes/<No>]? press Enter
Overlap method: Hold grid 1, replace with grid 2 or average [Hold/Replace/<Average>]?press Enter
Specify inclusion and exclusion areas for grid 2. Grid 1 used everywhere else.
Select the Inclusion perimeter polylines or ENTER for none. select perimeter(s) or press Enter
Select objects: press Enter to conclude selection
Select the Exclusion perimeter polylines or ENTER for none. select perimeter(s) or press Enter
Select objects: press Enter to conclude selection
Merged Grid File to Write Dialog(new file select dialog)

Pulldown Menu Location: Surface >> Modify Grid File
Keyboard Command: mergegrd
Prerequisite: Two grid (.GRD) files