Overlay/Merge

[dylancummings]

I am kind of stuck here. I have 3 or 4 different layers that demonstrate things such as population by zip code, average hospital transport time by zip code, etc...there are 4 layers with the data broken down to the zip code level for the state. How can I take all four of these layers and make a composite map showing which areas are in need for more services and which areas are not. My maps are just regular polygon maps and when i try to use the weighted overaly analysis tool it wants everything in raster not polygon. Can anyone help me with this process?

[curtvprice]

My maps are just regular polygon maps and when i try to use the weighted overaly analysis tool it wants everything in raster not polygon. Can anyone help me with this process?

You can easily convert the polygons to rasters using the Feature To Raster or Polygon To Raster tools. For best results, set the extent and cell size in the geoprocessing environment before you run the conversions so the four rasters will line up.

If you want to do the analysis on polygons, the tool you are looking for is Union, but it doesn't have the nice interface assigning weights - you'd have to do that yourself. (Union requires an ArcGIS Advanced ["ArcInfo"]  license.)

[dylancummings]

I tried using the feature to raster tool but i couldn't seem to understand the output. The areas of higher population and lower population on my polygon map didn't seem to translate to the raster because some extremely urban areas were a very light gray and others were very dark. Again, some of the rural areas were very dark and others were light gray. What is causing this?

[curtvprice · Accepted solution]

I tried using the feature to raster tool but i couldn't seem to understand the output. 

Did you specify a polygon table field to use for the raster value? if not it just uses the object ID. If the field value was just population you would need to normalize it the data by area (pop / area) and grid on that field (density) instead of just population count. The cell values will then be more appropriate for this kind of analysis.

[dylancummings]

Did you specify a polygon table field to use for the raster value? if not it just uses the object ID. If the field value was just population you would need to normalize it the data by area (pop / area) and grid on that field (density) instead of just population count. The cell values will then be more appropriate for this kind of analysis.

That did it. I was using the Feature to Raster instead of Polygon to Raster. The first time i also forgot to set my value to PopDens instead of the default FID