Binary Layers
- overlay by multiplying two binary risk layers
low hazard
0high harzard
1low hazard
0low risk low risk high hazard
1low risk high risk or adding them
0 | 1 | |
0 | ||
1 |
open overlay\overlay trials.mxd to try these in a model
use the xxdemo_overlay toolbox in the overlay folder to find the binary plus and times models
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Multiple Category Layers
- multiple boolean operators become very complex but can be done with a script
- overlay by adding or multiplying;
High Hazard | Mod Hazard | Low Hazard | |
High Hazard | high risk | moderate risk | low risk |
Mod Hazard | high risk | low risk | no risk |
Low Hazard | moderate risk | low risk | no risk |
But how would you "hand pick" various levels of risk as shown above, when the weighting is not symmetrical?
.
Index Layers
- use reclassify or map algebra to create indices
- overlay by adding or by multiplying has a different effect on the distribution of high and low results.From the file overlay\overlay trials.mxd,use the xxdemo_overlay toolbox in the overlay folder to run an index overlay.
Layer Weighting (can be combined with Overlay Types #1-3)
- one layer (or more) is more important or has more influence on the outcome than others
- use raster calculat or the "weighted sum" toolbox
- can use weighted overlay toolbox
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