GIS DATABASE DEVELOPMENT

DERIVING ELEVATION OF A SUB-SURFACE COVERAGE

The GRID command starts the GRID cell-based geoprocessing program

--use the GRID command to combine multiple grids on a cell-by-cell basis within analysis window, such that a unique output value is assigned to each unique combination of input values at GRID prompt:

: GRID {AML_command_file} this is the AML file created to set user-specified environments in GRID

GRID: combine

Starting with a topo coverage with point data that has no elevation at the surface

Make a 30m grid from the topo and a 30m point grid

**(the 30m grid fit all of the points without having 2 points in the same cell; if 2 points do end up in the same cell use a smaller grid size)

Use the Point Cover to Grid wizard in Arc Toolbox

OR

In Arc,

type:  

: pointgrid

grid: combine out_grid = combine borehole_grid, topo_grid

--this creates a new grid: out_grid

 Arc: tables  **have to use Arc because wizard will not convert files

: dir 

: Infodbase to out_grid.vat to surface.dbf file

Open .dbf file in Excel

Table will show elevation and borehole ID data

Make a 3^rd column named “Bedrock Elevation” that shows the distance between the first two columns

--save ID and bedrock fields as *.dbf files

: jointables 

: join to borehole data (file name)

--this will give you elevation of bedrock in the coverage

To generate a grid from the points:

: topogrid

This gives you the necessary data to construct a cross section from your coverage.

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