Geographic Information Systems
Bloomsburg, PA 17815
Maps By Mitch
Using Geoprocessing in ArcMap, step-by-step
July 28, 2011
Welcome to "Maps By Mitch". A "blog" of sorts to highlight various maps and the techniques used to create them. I hope to have a new "map" posted on a monthly basis.
This month's map is an adaptation of a recent real-world project. I wanted to demonstrate the power of geoprocessing tools such as "buffer", "clip", and "intersect". Tools such as these are staples of spatial analysis. If you have any questions reqarding the methods used, please contact me.
Purpose: I was seeking farmland or open space to rent in Columbia County in order to plant hay and straw which could be used as feed and bedding on my horse farm.
Requirements: 1) Farmland or open space that is twenty acres or greater. 2) A soil type that is conducive for planting hay and straw. 3) Location must be within approximately eight miles from my barn which is located in the Luzerne County portion of Berwick.
Design: I started by opening Esri ArcMap 10 and added the Municipalities layer to establish the spatial reference for the remainder of the layers that would be added. Then I placed a point graphic on the map to symbolize the location of the barn. After that I converted the graphic to a point feature which allowed me to use it in geoprocessing operations later, (Figure 1).
Figure 1. Location of Barn
I added the Soils layer for Columbia County and preformed a "Select by Attribute" query to get a selection of the soil types I wanted, which are follows: AaA, AaB2, AaC, BeB2, BeC2, CgA,CgB2, CgC2, CgD3, ChA, ChB2, Tf, Tg, Ts, Tt, WoB2, WoC2, WoD2, WpD, WsB, (Figure 2).
Figure 2. Select by Attribute, soil types
Using the point which represents the barn, I created a buffered zone of eight miles around the barn. The resulting geometry was then trimmed to the Columbia County boundary using the “clip” geoprocessing tool, (Figure 3).
Figure 3. Eight Mile Buffer
I then used the “clip” geoprocessing tool on the soils layer to trim the soil data to within the buffered geometry. Afterwards I added the Parcels layer for the county. Like the Soils layer, I clipped this layer to the eight mile buffer. Then I ran the “intersect” geoprocessing tool supplying the soils and the parcels layers. With the result, I used the “Select by Attribute” query to find the parcels that are 20 acres or greater and named the output “Parcels and Soils 20 Acres or Greater”, (Figure 4).
Figure 4. Parcels that are 20 acres or greater and contain the appropriate soils types.
Next, I added the landuse layer to ArcMap and used the “Select by Attribute” query to select the parcels that have the appropriate landuse code. Then took those selected features and ran a “Select by Location” query to select only those features within the buffered distance. I named the resulting layer “Agricultural Lands”, (Figure 5).
Figure 5. Agricultural lands via Select by Location.
I then took the “Agricultural Lands” layer which was created in the previous step and intersected it with “Parcels and Soils 20 Acres or Greater”, which was created in a prior step. I named the resulting layer “Proper Agricultural Lands/Soils/Parcels”, (Figure 6).
Figure 6. Intersection of Agricultural Lands and Parcels/Soils that are 20 acres or greater
Finally, I ran a “Select by Attribute” query on the “Proper Agricultural/Soils/Parcels”, which selected all of the polygons that contained the soil type(s), agricultural landuse, and areas of 20 acres or greater. Exported the selected data and named it “Appropriate Sites for Hay/Straw”, (Figure 7).
Figure 7. Appropriate Sites for Hay and/or straw
Conclusion: Twenty five sites were deemed acceptable sites to plant my hay and straw. The largest site being 63 acres and the smallest being 20 acres.