# Tutorial: Spatial Analysis of Accessibility of Wells using Map Algebra

## 1. Introduction

With *map algebra* we can do
calculations with raster layers. This is useful for spatial analysis.
For example, when we need to evaluate different criteria to find
suitable or unsuitable locations we can use map algebra.

After this lesson you will be able to:

- apply
*map algebra*for raster analysis - distinguish
*Boolean*,*discrete*, and*continuous*rasters - make legends for Boolean, discrete, and continuous maps
- understand the use of
*Nodata* - use
*logical operators* - calculate
*distances*from rasters *reclassify*rasters*convert*raster to vector points*sample*raster values with vector points

In this lesson we'll address the following case.

The
municipality of the (imaginary) oasis Aïn Kju Dzjis has hired you to
analyse which wells are unsuitable for its inhabitants based on the
following conditions:

The wells should be within 150 meters of houses or roads.

No industry, mine, or landfill within 300 meters of the wells.

The wells should be less than 40 meters deep.

You will use map algebra to perform the required analysis.

__Condition 1:__The wells should be within 150 meters of houses or roads.

__Condition 2:__No industry, mine, or landfill within 300 meters of the wells.

__Condition 3:__The wells should be less than 40 meters deep.

You will use map algebra to perform the required analysis.

This lesson will follow this workflow:

The raster layers for this lesson can be downloaded from the main lesson page.