If your GIS (geographic information system) is grid-based, you have access to some cool, algebra-based functions. The following table shows the functions, where they work, and what you can do with each:
| Function Type | Where It Operates | What It's Used For |
|---|---|---|
| Local | On individual grid cells | To change cell values based on user definition or the value of corresponding grid cells on other layers. |
| Focal | On a specifically targeted grid cell | To return a value (such as an average) based on the values of neighboring grid cells |
| Zonal | On grid cells in specifically identified regions | To calculate values based on analysis of specified regions that are not necessarily connected |
| Block | On square blocks of grid cells | To return a value for the identified block (for example, a 4 x 4 block of cells) on an output grid |
| Global | On the entire grid | To highlight hard-to-find features and spot general trends by moving through the entire grid |
| Specialty | On specified grid cells | To perform high-end statistical analysis or create models for moving surfaces (such as water or pollution) |