Introducing Geographic Information Systems with ArcGIS: A Workbook Approach to Learning GIS, 3rd Edition

Converting Zones to Regions to Find Individual Sites

You noticed from the attribute table that only four numbers appear in the Value column. This means that all the cells of the areas we are interested in (indicated by Value = 4) reside together in a single zone. A zone consists of cells that all have the same value. So, the areas that are candidates for the Wildcat Boat facility are all connected in a way—they are part of a single zone. You may recall that a raster region consists of one or more sets of disconnected cells that are in the same zone. That is, for a given zone, regions are clumps of cells that are completely disconnected from other cells in the zone. So it is the regions of zone 4 that we want as distinct entities that will form the individual sites we need. We can form these using the Region Group tool in ArcToolbox.

____ 37. Locate the Region Group tool in ArcToolbox. Where is it?

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____ 38. While you are in the Spatial Analyst Tools toolbox, count the number of sub-toolboxes in the Spatial Analyst toolbox. ________. Expand a few of the sub-toolboxes and note the number of tools. This is to say that this is a big chunk of software, all by itself.

Recall that the term “connected cells” can have two meanings. Cells can be connected by their sides, in which case each cell has up to four neighbors. Or cells can be considered connected if either their sides or corners touch, in which case each cell has up ...