How can I set a surface grid data range to display transparent?

Occurrence

The Surfaces>Modify Grid Display tool allows the transparency of an entire grid to be set.
But how can I set only a particular data range of a grid to be transparent?


Solution

To make only a certain data range in a grid transparent, you will have to permanently overwrite these
values with the Null value in the grid.  Any Null values in a grid will not be displayed.

Four methods for accomplishing this are:

1)       Use the Surfaces>Grid Utilities>Replace to replace all a value, with the value NULL.
To specify a range of values, simply use the median value in the range, and use half the total range
value as the tolerance.

For example to omit the range 5-10, replace the value 7.5 with a toelrance of  +/- 2.5, with "NULL".

2)       If you are colouring the grid by data breaks, and wish to apply a minimum cut-off threshold,
use Surfaces>Grid Utilities>Classify to classify each of your ranges to a value, and set the
transparent ranges  to the value NULL.

 3)      Write a simple equation in Surfaces>Grid Calculator, replacing the values if they are in a
range with NULL. Example syntax to remove values in the range of 5-10 is:

output = if (and(InputGrid<=10,
InputGrid>=5), null, InputGrid)

4)       Use Surfaces>Grid Query>Select By Value for values in the range, this will create polygon
bounds to these areas. Then use Surfaces>Grid Utilities>Overlay to replace the area under the
query polygon with NULL, and the background value would be set to the the input grid.


 

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Last Updated on: 24th of December, 2008