I am relatively new to GIS and I'm working on a practical for the assessment of areas sensitive to desertification using MEDALUS Method. To obtain the Sensitive areas, I am to compute the geometric mean of four quality indicators that is: soil, climate, vegetation and management quality indicators i.e.,
ESA = (SQI * CQI * VQI * MQI)^1/4
Where; ESA is Environmentally Sensitive Areas
SQI is soil quality indicator
CQI is climate quality indicator
VQI is vegetation quality indicator
MQI is management quality indicator
To get each quality indicator, I have to compute the geometric mean of the factors in each quality indicator. For example for the soil quality indicator, I'll use the slope, soil texture, Exchangeable sodium percentage, Electrical Conductivity and drainage to compute the geometric mean i.e.,
SQI = (S * ST * ESP * EC * DR)^1/5
Where; SQI is Soil Quality Indicator
S is slope
ST is soil texture
ESP is exchangeable sodium percentage
EC is electrical conductivity
DR is drainage
Each factor is broken down into classes and each class is assigned a weight index according to its influence on the sensitivity of the area to desertification. The weights range from 1 to 2.
Below is a table for the weights to be assigned to each slope class.
| Class | Description | Slope % | Index |
|---|---|---|---|
| 1 | Very Gentle to flat | <6 | 1 |
| 2 | Gentle | 6-18 | 1.2 |
| 3 | Steep | 18-35 | 1.5 |
| 4 | Very Steep | >35 | 2 |
How do I assign these weights to each class in ArcMap and use the weighted rasters to compute the geometric mean?
