Have you ever wanted to hide sections of the layers on your map but not wanted to clip your data to do so?
For example, you might want to show all of the 2D seismic available within your company’s license blocks, but hide the data when it is over another company’s blocks, as illustrated in the screen capture below.
Example showing difference between original and masked data.
Looks great, how do I do it?
You can use Definition Queries to build mask layers that allow you to hide areas of your data, without having to edit your original feature classes. To do this, use the following workflow:
1) Create a copy of the layer which you will be using as a mask, by copy/pasting it into your data frame – in this example I use an offshore licenses layer (represented by polygons) to mask a 2D seismic lines layer, so I make a copy of the offshore license layer.
2) Use the Definition Query tab in the Layer Properties dialog to exclude your area of interest – for example, “OPERATOR” <> ‘YOURCOMPANY’ – from the copied layer. The new layer now has ‘holes’ in it where your licenses are and, if placed above the 2D seismic lines layer in your Table of Contents, it will mask out the 2D seismic lines in other companies’ license blocks. At this point you have achieved the objective, as shown in the screen grab below.
The result – 2D seismic lines masked using a license layer with a definition query applied.
But wait, there’s more!
The technique described above is great if you simply want to mask everything in the layers below the masked layer. However, if you wish to have more freedom in how you order your layers, it is possible to apply the mask to a specific layer (or layers), using Advanced Drawing Options.
To demonstrate this functionality, I have chosen to mask the 2D seismic lines so that only the seismic lines available in ‘current and never previously licensed’ blocks are visible. To do this, use the following workflow:
1) Create a Definition Query on the license layer which excludes the current and never previously licensed areas – e.g. “COMMENTS” <> ‘Current (never prev. licensed) area’
2) Right-click on the Data Frame title and select Advanced Drawing Options from the context menu:
The dialog shown below will appear:
3) Check the Draw using masking options specified below box, then:
a. Select the layer to use as the mask.
b. Select the layer(s) that you wish to mask.
c. Click Apply to view the result.
4) The result is a masked layer that you can move around in the Table Of Contents, without having to worry about obscuring information information in other layers that you want to appear on your final map. Note that you can now switch off, in the Table Of Contents, the layer that you are using as the mask.
Posted by Devlyn Robson, GIS Trainer, Exprodat.
