know what land uses will be affected by the new bylaw. You have a GIS theme on landcover/landuse in the area. Your task: a. Create a 100-foot buffer around identified wetlands in Lynn b. Identify what types of land uses are within 120 feet from the buffer zones. STEP1: DISSOLVE 1. Start ArcMap. 2. Add the shapefile polygon layer containing data for land use for the town of Lynn – lus163p1.shp (this is from MassGIS) 3. Make Land Use the active theme, right click and open the attribute table. As you can see there are 298 features in this layer. 4. Scroll to the right and look at the “Descriptio” (description) field. Recall that land use is classified into 21 categories. By using Dissolve, you can reduce the number of features from 298 to 21. With fewer features to process, subsequent geoprocessing tasks will take less time and will be less confusing. 5. Close the table. Click the icon to show ArcToolbox application. Navigate to Data Management Tools- Generalization-Dissolve: Dissolve Tool 111 ArcToolbox Show/Hide icon Dissolve Wizard The ArcToolbox suite of tools has some *really* useful functions, similar to some of the “Select by location” queries we were doing in another analysis exercise. The difference is that these functions create a new layer – the “Select by location” under the selection tool just makes certain layer features active or “selected”. It is in ArcToolbox that you can perform the VECTOR OVERLAY functions. Some of the tools organized in ArcToolbox allow you to merge themes together into one, clip out one theme based on the geographic extent of another theme, intersect or union of two themes, among lots of other useful operations you may need to perform with your vector data. But here we’ll use dissolve. 1. For the input features, scroll or browse to select the data set you want to dissolve: lus163p1.shp 2. For the “Output feature class” navigate to your work folder (e.g., c:tempgisdata), but change the file name: 21_landuse.shp 3. For the attribute to dissolve, choose “DESCRIPTIO” in the dropdown list. 4. SCROLL DOWN… In the “Statistics Field” click AREA, and under “Statistic type” click SUM. Do the same for PERIMETER. (This will create these two columns in the output attribute table with these sums.) Click OK. You’ll see it “dissolving…” and eventually 21_landuse.shp will appear in the table of contents. 112 Source.