Spatial Analysis of Accessibility of Wells using Map Algebra
In this tutorial we'll apply map algebra to determine the accessibilty of wells. This tutorial was developed together with Kurt Menke (Bird's Eye View GIS).
3. Condition 1: Wells within 150 Meters of Houses or Roads
3.2. Create a Boolean Layer with True for Houses and False for Other Buildings
If we want to create a Boolean layer with True (1) for houses and False (0) for the other classes in the buildg layer we can use the Raster Calculator.
1. In the main menu go to Raster | Raster Calculator.
2. In the Raster Calculator dialogue double-click on buildg@1, click the = button and type 1.
Now the equation reads buildg@1 = 1, which means: if the buildg@1 layer equals 1 (which is the houses class), then the output layer has True (value 1), else it has False (value 0). @1
means band 1. In our case we only use single band raster layers
(multiple bands are used in other applications such as remote sensing).
3. Call the output layer houses.tif and click OK to perform the calculation.
Following good practice, we are going to style this Boolean layer. For Boolean layers we also use the Paletted/Unique values renderer.
4. Repeat steps 1 and 2 of lesson 4.1 to style the houses layer and choose intuitive colors for True and False.