How do I populate/update vector data with values from a gridded surface?

Occurrence

Some examples of use:

- Updating regional RAB drillhole collar locations with accurate RL's from a topographic grid surface provided by a geophysical contractor
- Assigning geological, regolith or tenement polygons mean or maximum copper assay vlaues from an underlying gridded geochemical surface (created using IDW interpolation) as part of prospectivity mapping


Solution

1/. Ensure that the vector data table has the necessary numeric field/s to capture grid data into, using the Table>Maintenance>Table Structure tool. For example, if populating a drillhole collar table with RL values from a DEM grid, create an 'RL' or 'Elevation' field with a Float type.

2/. Open into a map window both the vector table to update, and the source grid.

3/. Select the vector data to update, using either a graphical selection tool (to select a subset of the vector data), the Select All menu option in the ELC (to select all objects in the vector table), or a Query.

4/. Open the Surfaces menu (Discover>Surfaces menu) and select the Assign Values from Grid option.

5/. If updating point data (a one to one relationship), the following dialog will prompt for a destination field (e.g. the RL field example in step 1).

6/. If updating polygon or polyline data (i.e. a many to one relationship: for example, populating tenement polygons with the average  values from a regional copper soil sampling grid), the dialog will prompt for destination fields for Average, Minimum and Maximum values. The user can specify one or multiple of these output calculations.


7/. Press OK to run the calculation. The results can be viewed by opening a browser window of the vector table, and scrolling to the destination field/s.

8/. Select File>Save Table and select the updated vector table to make these changes permanent.

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Last Updated on: 1st of September, 2009