and navigate to F:\usertemp\siteselection_iap07)Site Selection - Making Spatial Decisions Using GIS
We will use the following tools to select a site for a new visitor center at a National Wildlife Refuge in Concord, Massachusetts.
• Clip trims all layers to a more manageable extent.
• Buffers create an area of designated size around a feature.
• Union combines the attributes of two layers to create the sum of their
spatial extent.
• Symmetrical Difference reverses the coverage of a layer within another
layer.
All of the data used in this exercise can be downloaded (free of charge) from the MassGIS website ( http://www.mass.gov/mgis/laylist.htm ). To look for more data on the web and at MIT, see this MIT Libraries GIS webpage: Spatial Data at MIT ( http://libraries.mit.edu/gis/data/index.html )
Start ArcMap with a new, empty map (start-> all programs
-> arcgis-> arcmap)
Add all data layers from the class file. (Click on the add
data button and navigate to F:\usertemp\siteselection_iap07)
Add data layers from the MIT Geodata Repository
After performing the search, highlight the layer and click on ->Add Selected Layer to Map
Add projection information to the Data Frame
In the view menu, click on Data Frame Properties. Click on the Coordinate System tab. We will define the coordinate system for the entire map using a coordinate system from the towns layer to set the data frame coordinate system. Click on the Import button, and choose one of the EOTROADS_ARC shapefiles. These layers came from the MassGIS website with their coordinate systems attached.
Make sure your Data Frame Properties Dialog matches the image below.
Move the Great Meadows layer to the top of your table of contents by clicking on it and dragging it to the top of the list. Right click on Great Meadows and click on Zoom to Layer. Note that a large portion of the property is within this Rare Species Habitat. This is good for the rare species, but NOT a place for a visitor center.
Experiment with the layers, turning them off and on, moving them up and down in the table of contents to get a better understanding of the site. There is a lot of water, and very few roads intersect the property.
Use the Zoom to Full Extent button 
to see all the data you have loaded. The data covers the entire state of Massachusetts,
but to focus our work, we will select and work with data in three towns that
contain Great Meadows National Wildlife Refuge: Bedford, Carlisle and Concord.
In the Table of Contents, right click on townsp1 then, click on open attribute table. At the bottom of the Attributes table, click on the Options button. Click on Select by Attributes. This opens a new window. Make sure the Method is: "Create a new selection." Scroll down to and double click on "TOWN", (NOT "TOWNS_") then click on =, then click on the Get Unique Values button in the center of the window. This displays all the town names. Double click on 'BEDFORD' then click the OR button, and repeat this process to include 'CARLISLE' and 'CONCORD". Make sure your panel matches the following graphic, then click Apply.
At the bottom of the Attributes of townsp1 table, click "Selected" to show only the towns you have selected. Close the Attribute Table.
In the Table of Contents, right click on townsp1. Move your pointer to Data, and click on Export Data. Make sure the Export dropdown menu says Selected features. Use the same coordinate system as this layer's source data, and save the file in F:\usertemp\siteselection\ as BedCarCon.shp. You will be prompted to add the exported data to the map as a layer. Click yes. You will see the layer called BedCarCon appear in your Table of Contents. Turn off the selected features by clicking on the Selection menu, and then on Clear Selected Features. Remove the townsp1 layer by right clicking on the layer name in the table of contents, and left click on remove.
SAVE YOUR MAP.
Clip the hydrography [wetdep_concp1.shp], rare species habitat [sde_data.us_ma_d5prty_2003], and vernal pools [sde_data.us_ma_d5vernl_2003] layers to the GreatMeadows layer property boundary, so you can concentrate on the important portion of your map (the map will redraw more quickly without all the extra data).
Open ArcToolBox. (It's the little red box on your tool bar. It's also in the Window menu.) Under Analysis Tools->Extract, double click on Clip. The Input Features (that you will be clipping) are contained within wetdep_concp1.shp. The Clip Features are contained in GreatMeadows. Name the Output Feature Class file Hydrography.shp. Save it in F:\usertemp\siteselection\. Leave cluster tolerance blank.
Make sure your dialog matches the following graphic and click OK
Repeat this proceedure for the the Input Feature Class sde_data.us_ma_d5prty_2003. Name the Output Feature Class SpeciesHabitat.
Repeat this proceedure one last time for the the Input Feature Class sde_data.us_ma_d1cvp_2006. Name the Output Feature Class VernalPools.
Remove the layers called sde_data.us_ma_d1cvp_2006, sde_data.us_ma_d5prty_2003, and wetdep_concp1, and townsp1, by right clicking on their names in the Table of Contents and clicking Remove. Now you can concentrate on the important portion of your study area.
Right click on BedCarCon and click Zoom to Layer. Move GreatMeadows to the top of the Table of Contents.
Click on the VernalPools symbol in the Table of Contents. Change the symbol to Circle 2. There is one Certified Vernal Pool on the property.
Move the GreatMeadows layer to the top of the Table of Contents.
Move the SpeciesHabitat layer to second in the table of contents. Note how much of the southern portion of the property is covered with this layer, including the area where the vernal pool is located.
Click on the zoom in tool 
and
draw a box around the Northern portion of the property that is not covered by
SpeciesHabitat.
Symbolize the hydrography data
In the table of contents, right click on Hydrography. Open the Attribute table and find the name of the attribute that describes each area within the layer. It is IT_VALDESC. Close the Attribute table. Right click again on Hydrography and click on Properties. This opens the Layer Properties dialog. Click on the symbology tab. In the show box, choose Categories, and Unique Values. Choose IT_VALDESC in the value field. Click on the Add All Values Button. Uncheck All Other Values. Click OK. Now you can see the different types of hydrographic features on the property.
Buffer the hydrography data
In Massachusetts, buildings must be located at least 50 feet from all hydrologic features and wetlands. We will select the features on the property that have to be buffered. They are: Deep Swamp, Open Water, Shallow Marsh Meadow or Fen, Shrub Swamp, and Wooded Swamp Deciduous, and Wooded Swamp Mixed Trees. The only feature that will offer us potential building sites is called Upland.
Right click on Hydrography, and click on Open Attribute Table. Click on the Options button at the bottom of the table and click on Select by Attributes.
Double click on "IT_VALDESC", Click =, click the Get Unique Values button. Double click on 'Deep Marsh'. Click on OR. Continue this process until each of the features listed above are added.
Make sure your Select by Attributes dialog looks like the image below, and click Apply.
Close the Attributes of Hydrography table.
To create the buffer we need the buffer wizard, which gives us more options than the buffer in ArcToolbox.
From the Help menu, open ArcGIS Desktop Help. Click on the index tab. Search for Buffer Wizard. Follow the directions for how to add the Buffer Wizard to the Tools menu. Open the Buffer Wizard. Within the wizard choose Hydrography as the layer whose features you want to buffer. Make sure the "use only the selected features" box is checked and click next.
Set the Buffer Distance Units to feet (at bottom of dialog box), and make the specified distance 50 feet. Click Next.
Say yes to dissolved buffers, create buffers so they are outside polygons and include inside, and save the buffer as a layer. Click Finish.
Look at the Buff_of_Hydrography layer. Note the extra area around features other than Upland.
Create a Union between the Rare Species Habitats and the Buffered Hydrography layers.
We want to eliminate any area within the property boundaries that includes Rare Species Habitat and the Hydrography features with their buffers. When we Union the two layers called Buffer_of_Hydrography and RareSpecies we will see all the areas on which we should not build.
(Open ArcToolbox->Analysis Tools->Overlay->Union)
From the dropdown menu, choose Buffer_of_Hydrography and RareSpecies for the Input Features.
Name the Output Feature Class NotUsable. Click OK.
Turn off the Buffer_of Hydrography, VernalPools, and SpeciesHabitat layers. Turn off the selected features by clicking on the Selection menu. Click on Clear Selected Features.
You can see the exposed Upland from the Hydrography layer around the NotUsable layer.
Use Symmetrical Difference to create a layer that shows only the usable areas on the property.
(Open ArcToolbox->Analysis Tools->Overlay->Symmetrical Difference)
Choose NotUsable for the input features, and GreatMeadows for the Update Features
Name the Output Feature Class Usable.shp.
This layer shows the areas on the property that are acceptable for use to build the Visitor Center.
Turn off the NotUsable and Hydrography layers.
Move the EOTROADS_ARC_Bedford layer to the top of the Table of Contents. Click on the road symbol in the Table of Contents. Change the width to 4. Click OK. Right click on EOTROADS_ARC-Bedford and click on Label Features.
Zoom in on the area where roads intersect the Usable layer. These are the areas with road access that you have left to build your visitor center. They are on Uplands, 50 feet away from any water feature, and do not contain rare species habitat or certified vernal pools.