A module for easy import of Geoplot 3.0 ASCII data. Note that Geoplot data is in a local, non-geodetic reference system. Another tool such as v.transform will commonly be necessary to georeference and integrate it with existing data.

Geoplot is produced by and copyright of Geoscan Research.


This module provides a way to import Geoplot data at full resolution and precision into GRASS GIS in a straight-forward manner. It is assumed that the user has already fully post-processed the raw data, applying filters, normalizing value ranges etc. as needed in Geoplot. Data should then be exported from Geoplot as ASCII values so they can be read and converted to a vector map with this module.

The result of the import operation will be a new vector points map with each point representing exactly one record of the input file. Each record's nanotesla value will be stored in the double precision type field "nt" of the result map's attribute table. In addition, the original (local grid) coordinates of the record will be preserved as attribute fields "x" and "y".


Geoplot is capable of producing a variety of different ASCII formats. The recommended way is to export "XYZ" files. However, lists of only Z values can also be imported, in which case the xincrement=, yincrement= and length= options have to be specified. All other export options, specifically the delimiter character, the NULL value representation and the "reference corner" are matched by equivalent options of If no value is given fort null=, all records will be imported.


Given a Geoplot XYZ ASCII file named "" with the following structure:
0       0       1.374888
.125    0       1.074888
.25     0       .9748878
.375    0       .8748878
.5      0       .6748878
.625    0       .2748878
.75     0       .3748878
.875    0       .5748878
1       0       .8748878
The correct syntax is: out=readings null=2047.5
This will create a new vector map "readings" with the import result.


Benjamin Ducke, benjamin.ducke AT

Last changed: Mon Sep 28 2009