GIS EXERCISE 4. Department of Urban Studies and Planning Spring 2006 Department of Architecture Site and Urban Systems Planning J / 4.

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1 Department of Urban Studies and Planning Spring 2006 Department of Architecture Site and Urban Systems Planning J / 4.255J GIS EXERCISE 4 Objective: To understand how suitable/costly developable land is through: Creating buffers Intersecting shape files Converting vector data to raster data Assigning values to raster data Performing raster calculations Xtools STEP 1: Create buffers 1. From a new ArcMap document, set the data frame to NAD_1983_StatePlane_Massachusetts_Mainland_FIPS_2001. For a reminder of how to do this, consult GIS Exercise 1, Step Make sure you are displaying feet by clicking View>Data Frame Properties and selecting the tab marked General. Change Display to Feet. 3. Now, insert the following file: \11.304j\hopkinton\GIS\Data\Roads Rail\EOTROADS_ARC_139.shp 4. Next, insert the site_all.shp file from \11.304j\hopkinton\GIS\Data. 5. Using the selection tool, draw a box around the site to select all the roads that traverse our site. Next, right click on the layer EOTROADS_ARC_139 and choose Data>Export Data. Save your file as roads_temp to your own working folder Site and Urban Systems Planning Page 1 of 6

2 6. Open ArcToolBox (the red tool box) and select Analysis Tools>Proximity>Buffer 7. Next, drag and drop road_temp into the Input Features category. Choose to save the Output Feature Class as roads_buffer.shp. Change the metric to Feet and enter 30 next to it. FULL is the correct option to choose for Side Type (so, we are offsetting 30 feet on either side of the center-line). Choose FLAT under End Type so that we don t offset around the ends of each line (you ll obviously want to change this feature back if you are doing buffers around wetlands, etc.). You ll notice that we haven t chosen the correct buffer distance or separated the roads into classes of ROW distances. I leave that exercise up to whoever is focusing on roads. This example is only meant to demonstrate how to use the software. STEP 2: Intersect shape files 1. Next, we will intersect the two shape files to get a final road shape file. In ArcToolBox, select Analysis Tools>Overlay>Intersect. Drag and drop roads_buffer and site_all into the Input features category. Save the new output as roads_site. 2. You may remove the other road layers you ve accumulated. We will only need the roads_site layer now. 3. Next, insert the following shape file: P:\11.304j\hopkinton\GIS\Data\Title 5 Buffer\t5_concp1.shp. The shape file you just inserted doesn t have a projection associated with it yet but it has assumed the projection you set your dataframe to earlier. You can set a projection for the file later in ArcToolBox (Data Management Tools>Projections and Transformations>Define Projection). For now, we re OK with it because we are only interested in a portion of the shape file. 4. Repeat the first step to intersect t5_concp1 with site_all. Save the new file as t5_site Site and Urban Systems Planning Page 2 of 6

3 5. Insert the following file: P:\11.304j\hopkinton\GIS\Data\Soil\soil_ma017\spatial\ soilmu_a_ma Repeat the first step again to intersect it with site_all. Save the new file as soil_site. 7. Add the slope raster file that you created in GIS Exercise 2, Step 5. Reclassify the raster image to the following slope values: 0-5; 5-10; 10-15; and >15. Review GIS Exercise 2 if needed. STEP 3: Convert vector data to raster data 1. Four of our layers are vector based and one of our layers is now raster based. We will now convert all of our features to raster data. To do this, we will need to use Spatial Analyst. Right click on a portion of the tool bar and ensure that Spatial Analyst is checked. Alternatively, choose Tools>Extensions and check Spatial Analyst. 2. Click on the Spatial Analyst toolbar and choose Convert>Features to Raster 3. Choose soil_site as the Input features, change the Output Cell Size to 10, make sure that the Field is musym and save it as soil. 4. Repeat the process for t5_site, choosing the Field as Inside this time. Repeat again for roads_site, choosing CLASS as the Field. 5. Now, we have converted our vector data to raster data. However, these new raster data sets are surrounded by null space. For example, the raster data for our roads layer is suspended in space and not surrounded by other raster data values. If we were to join this roads layer with another raster data set, we would lose any data where null space existed. To avoid this predicament, we must write a conditional statement in Spatial Analyst for each of our new data sets. First, we must set some parameters. Click on Spatial Analyst and choose Options. Select the Extent tab. For Analysis extent, choose the recently made soil raster layer. Next, select the Cell Size and choose the Soil raster again. This will ensure that we make new rasters that completely cover our site since our soil raster is the same shape as our site. PLEASE NOTE THAT IF YOU WANT TO CREATE A LARGER ANALYSIS OF LAND ABUTING THE SITE, YOU WILL NEED TO ADJUST THE EXTENTS TO A LARGER SIZE (SUCH AS THE SLOPE FILE S EXTENTS). 6. Click on Spatial Analyst again and this time choose Raster Calculation. Type the following conditional statement for the raster layer roads roads : Con(Isnull([roads - roads]), 0, [roads - roads]). Repeat the same process for the title 5 layer as well. The conditional statement follows the following pattern: Con(Isnull([raster_chosen_from_list]), 0, [raster_chosen_from_list]) Site and Urban Systems Planning Page 3 of 6

4 STEP 4: Assign values to raster data 1. Reassign values to our slope layer by clicking on Spatial Analyst and choosing Reclassify. 2. On the left side of the chart, you will notice our initial slope groupings. Now we will assign associated values to our slope ranges to reflect the additional costs to build on steep slopes. Enter 1 for 0-5 slope, 2 for 5-10, 50 for and 1000 for >15. Save the output raster as slope_cost to your working folder. 3. Repeat step 2 for our roads calculation. In this case give 0 a new value of 0 and 3, 5 and 6 new values of 1000 each. Save this new raster as road_cost to your working folder. 4. Repeat step 2 for our title 5 calculation. Assign old values of 0 the same 0 value and old values of 100 a new value of 500. Save this raster as t5_cost to your working folder. 5. For the purposes of this exercise, we will simply classify the groupings in the properties menu (i.e. this won t be a rigorous analysis of actual soil suitability). There are currently 35 distinct soil values for our site. These values will need to be grouped for suitability before being reclassified. I leave that bit of fun up to our soil experts to accomplish. Right click on the soil layer and choose Properties. Choose the Symbology tab and click on Classify. Next to Method, choose Defined Interval. The Interval Size should be set to 7. Press OK twice. Now, repeat step 2 for our soils layer and save it as soil_cost. The new values can be 10, 25, 50, 100 and 500. STEP 5: Perform raster calculations 1. We are now ready to finally build one raster data set to analyze the costs/suitability for development on our site. Click on Spatial Analyst and choose Raster Calculator Site and Urban Systems Planning Page 4 of 6

5 2. Double click one of the cost raster data sets we just made and then select the addition button. Repeat for each of the four cost raster data sets, adding them all together and then press Evaluate. 3. Right click on our Calculation and choose Properties. On the Symbology tab, choose Classify. Under select 5. Choose the following break values: 25, 50, 100, 500, and Press OK twice. 4. Reclassify the Calculation with new values equal to the aforementioned break values and save the new file as site_cost. STEP 6: Export raster to features and use Xtools (optional step) 1. Choose Spatial Analyst>Convert>Raster to Features 2. Accept the default entries and save the shape file as site_cost to your working folder. 3. Choose Tools>Extensions and check Xtools Pro Site and Urban Systems Planning Page 5 of 6

6 4. I want to discover how much area is in each of the value categories we made for our site. Select Xtools Pro>Table Operations>Calculate Area, Perimeter, Length, Acres, Hectares. 5. Select site_cost as the layer to measure. The Desired output units should be Feet. Uncheck Perimeter and Hectares (only check Area and Acres). Press OK. 6. Right click on site_cost and choose Open Attribute Table. Examine the new columns for Area and Acres. 7. Select Xtools Pro>Table Operations>Export Data to MS Excel. Select GRIDCODE, Area and Acres as the fields to export from site_cost and press OK. 8. In Excel, choose Data>Pivot Table and Pivot Chart Report. Press Next twice and then Finish. The data that we just imported should be selected for the pivot table. 9. Drag and drop GRIDCODE into the left column and Acres into the right column. We now know how many acres reside in each cost category Site and Urban Systems Planning Page 6 of 6