Spatial Analysis of Forest Landscapes: Point Events and Spatial Joins in ArcMap, Lab Reports of Forestry

Download Spatial Analysis of Forest Landscapes: Point Events and Spatial Joins in ArcMap and more Lab Reports Forestry in PDF only on Docsity! Spatial Analysis of Forest Landscapes 36 LAB 2- Adding Point Events ArcMap has the ability to read locational coordinates from tables and to convert those coordinates into point shape files. This feature may be particularly useful for researchers that are using GPS to record plot locations, study sites, or other information. For our example in the Siuslaw National Forest, a researcher has located Spotted Owl Nests in our study area and has used a GPS unit to record the locations. Fortunately, the locations are recorded in the same projected coordinate units as our database. He has made the coordinates available to us as a text file and they are stored in “owlnests.txt” in our workspace lab1 folder. Let’s return to our lab1 map document file and save it as lab2.mxd in the same folder location. Choose the Add Data and open “owlnests.txt” from your c:\advgis\lab1 folder to add the coordinate file to the table of contents. You will need to right click on this file and choose open to view the contents of the coordinate file. You should see a table similar to the graphic below. With the Study Area data frame active, let’s add these coordinates to our ArcMap session: 1. From the Tools menu choose “Add XY Data” Spatial Analysis of Forest Landscapes 37 2. Choose the XY button 3. In the Table input box, select “owlnests.txt” 4. Choose the fields containing the coordinate information (Xcoord and Ycoord) 5. Your input choices should look similar to the graphic below. If they don’t, make corrections. If they do match, press OK. Spatial Analysis of Forest Landscapes 40 We’ve created a shapefile from sets of coordinates that were stored in a text file. These coordinates could also have been stored in a dBASE or INFO file- the process for making a shapefile from them would’ve been the same. Save your map document so we don’t lose any of our progress. Let’s copy the “Vegetation Type” layer into the Study Area data frame: 1. Turn the “Ownership” layer off 2. Right click on the Vegetation layer and choose Remove from the popup menu 3. Click and drag the Vegetation Type layer from the Vegetation data frame to the Study Area data frame- place it below the Ownership layer. Change the symbology of the Vegetation Type layer to demonstrate the different descriptions: 1. Double click on the Vegetation Type layer 2. Access the Symbology tab 3. Click once on the Categories choice in the Show box and click on Unique values underneath Categories 4. Use the drop down menu and choose “VegType” in the Value Field box 5. Uncheck the “all other values” box 6. Delete the “VegType” listing in the Label column (highlight and choose delete from the keyboard) Spatial Analysis of Forest Landscapes 41 7. Check the “Add All Values” button and, if you’re happy with the color scheme, choose OK (otherwise select your color preferences before choosing OK). Judging from what we can see in the view, most of the owl nests, with one exception, are located in natural stands. These are forested areas that haven’t been harvested for over 50 years. Spatial Analysis of Forest Landscapes 42 Let’s turn the ownership layer on to see if any patterns exist. It appears that five of the nests are in forested areas owned by Siuslaw National Forest; the rest are on private lands. Spatial Analysis of Forest Landscapes 45 The Intersect command in the Analysis Toolbox is probably best since there is a shapefile involved in our analysis. Click on the Intersect (Analysis) option under the Tool column and choose Locate. Open the Intersect command dialog box by double clicking on it. 1. Add the Owl Nests layer to the Input features. 2. Add the Ownership layer to the Input features. 3. Set the Ouput Feature Class to: C:\advgis\lab1\nest_own_int.shp 4. Choose OK to run the process. Spatial Analysis of Forest Landscapes 46 The result of the Intersect command should be a shapefile of the results added to your table of contents. Open the attribute table of the new layer to view the tabular results. Close the attribute table. Close ArcToolbox. Spatial Analysis of Forest Landscapes 47 Spatial Joins as Overlay Processes There may be cases when a classic overlay command (union, intersect, identity) will not be appropriate for investigating spatial relationships. Consider the case of examining relationships between points and lines, and between databases that don’t coincide spatially. Points and lines represent very discrete locations and, unless they coincide exactly, there will be no geometric intersections unless some sort of buffering or change in intersection tolerance occurs first. Similarly, if a point layer doesn’t coincide with a polygon layer’s area, there will also be no output from a classic overlay command. One may still, however, wish to know what distance separates point features from other polygon features, or from other line features. A solution to these circumstances that is available in ArcMap is a spatial join. This bases the joining of two tables on the spatial relationships of their respective features. The type of spatial join and the outcome depends on the feature types that we are joining: points, lines, or polygons. The process for spatial joining is very similar to the process we learned for regular joining of attribute tables. One primary difference is that we are using the shape field, rather than an attribute field, as the common join field. Another primary difference is that the result is output into a new database. There are three types of spatial joins: nearest, part of, and intersects. Match each feature to the closest feature or features - In this association, you can either append the attributes of the nearest feature or append an aggregate (i.e. min, max etc.) of the numeric attributes of the closest features. Match each feature to the feature that it is part of - In this case, the attributes of the feature for which the current feature makes up a portion are appended. Match each feature to the feature or features that it intersects - Like with the closest feature(s) association above, you can either append the attributes of a single intersecting feature or an aggregate of the numeric attributes of the intersecting features. Let’s practice using spatial joins. For our first task, let’s use a spatial join to repeat the previous analysis of determining the ownership category that each of our owl nests is located in. This will be an inside spatial join: 1. Make sure the “Study Area” data frame is active 2. Right click on the Owl Nests layer 3. Choose Joins and Relates, then Joins 4. Change the first option to “Join data from another layer based on spatial location” 5. Select Ownership for #1 6. Make sure the “it falls inside” option is checked Spatial Analysis of Forest Landscapes 50 Choose OK to set the spatial reference. Double click on the lab2.mxd file in the left or right pane to reopen your ArcMap session. Start the spatial join process again by right clicking on the Owl Nests layer. Use the same settings we tried to apply last time (you can use the graphic below as a guide) and choose OK to create the output. Spatial Analysis of Forest Landscapes 51 A new shapefile named owl_owner is added to the table of contents. Right click on the new shapefile and open its attribute table. The attribute table includes variables from both layers that were included in the spatial join process. For each of our nests (Nest_id), we can now see an ownership category (Own). The output table tells us that five of our nests fall in National Forest lands and three are on private lands. It’s a good idea whenever possible to see if results match what we see on the view (or our expectations of data relationships). In checking the distribution of Owl Nests against our Ownership categories, it appears that the results are correct. Close the table when you are finished with your comparison. Spatial Analysis of Forest Landscapes 52 Let’s examine how spatial joins work between non-coincident features: determine the proximity of owl nest locations to the nearest road. This will be a nearest spatial join: 1. Right click on the Owl Nests layer 2. Choose Joins and Relates, then Joins 3. Make sure the first option is set to “Join data from another layer based on spatial location” 4. Select Road Type for #1 (the layer to join) (use ArcCatalog to add spatial reference information if necessary) 5. Choose the second option for #2 (Each point will be given the attributes of the line that is closest to…) 6. Write the result to your c:\advgis\lab1 folder and name it “owl_roads.shp” 7. Choose OK Spatial Analysis of Forest Landscapes 55 LAB 2 Application: Mapping and Analyzing Forested Monitoring Sites A stream ecologist has designed a study plan that involves installing stream gauges and smolt traps on selected streams within our study area. She has used a statistical sample in conjunction with USGS 7.5 minute quadrangle maps to select the monitoring sites. She is interested in getting information about her study locations so she can began to plan her field season and, to contact property owners to seek permission to begin her monitoring. She has pulled UTM longitude and latitude coordinates off of a digital raster graph version of her USGS maps and has passed them on to you. A file named “strmgage.txt” exists in the c:\advgis\lab1 folder that contains this information. You are to copy the roads, streams, ownership, and vegetation layers to a new data frame in your lab2.mxd project. Name the new data frame “Stream Gauges.” Your next task is to create a point layer from the coordinate event table and to create a shapefile named “strmgage.shp” from the point layer. The process for creating layers from a coordinate event table was detailed in the lab presentation we just finished. To summarize what you should do: 1. Create a new data frame, and name the new data frame “Stream Gauges” 2. Copy the layers you need from “Study Area,” 3. Choose the Add Data button 4. Add the table named “strmgage.txt” to your Stream Gauges data frame 5. Choose “Add XY Data” from the Tools menu 6. In the Table list, select “strmgage.txt” 6. Choose the fields containing the coordinate information (Xcoord and Ycoord) 7. Press OK This process should add a point Events layer to your data frame. Convert this layer to a shapefile: 1. Right click on the point Events layer 2. Choose Data, then Export Data 3. Write the output to “strmgage.shp” on the c:\advgis\lab1 drive. 4. Add the shapefile to your data frame. 5. Remove the layers named “strmgage.txt Events” and “Strmgage.txt” from your data frame. Make the new layer visible and enlarge the size of the gauge locations. Change the name of the layer to “Stream Gauges.” Your data frame should look similar to the graphic below. Spatial Analysis of Forest Landscapes 56 The stream ecologist would like us to answer a few questions for her regarding potential stream monitoring locations. In the last exercise, we practiced using overlay processes to examine spatial database associations. Use a combination of the classic overlay commands and spatial joins to answer the questions below. When spatial joins are used, the “Stream Gauges” layer will serve as the target of the spatial join. The layer that will be joined to the target will depend on the attribute question that is being posed. You will probably need to define the projection of the Stream Gauges and Stream Type layers- ArcMap will let you know when you perform a spatial join whether this is necessary. Spatial Analysis of Forest Landscapes 57 Lab 2 Application Please answer the questions below and submit your typed answers by the lab due date (see syllabus). For all four questions, use the Gauge_ID field and create a table to present your results. You should sort the Gauge_ID field from lowest to highest when reporting answers. For numeric answers, please only report to the nearest integer (no decimals) and indicate measurement units. 1. For each stream gauge location, what is the ownership? 2. For each stream gauge location, what is the vegetation type? 3. For each stream gauge location, what is the nearest stream type and how far away is it? 4. For each stream gauge location, what is nearest road type and how far away is it? Save your map document! Spatial Analysis of Forest Landscapes 60 Creating a layout From the View menu in ArcMap, you can switch between data and layout views of your map document. Up to now, we have been operating in a data view. Let’s go ahead and use this option to switch to a layout view. Spatial Analysis of Forest Landscapes 61 You could also have accomplished this by using one of the buttons in the lower left hand corner of the viewing area. Regardless of the method used to switch views, you should instantly notice a change in the map display area. In addition, a new layout tool bar should become available to you when you activate a layout view. Spatial Analysis of Forest Landscapes 62 The Page and Print Setup option under the file menu will let you chose the page orientation and dimensions. You can also access Page and Print Setup by right clicking in the blank space in the map display area and choosing this option from the pop up menu. Call this option and set both the Paper and Map Page Size options to Landscape. Spatial Analysis of Forest Landscapes 65 mouse- you should see “handle bars” around the data frame after you select it. Once it’s selected chose the Legend option from the Insert menu. This should open a dialog box that will allow you to select the layers within a data frame that appear in the legend. Bear in mind that the active (highlighted in bold) data frame will be the one that the legend information is drawn from when you select the Legend option. Our intent at present is to see the legends for the all of the layers. Choose Next and continue to do so until you seen an option for a Finish button (choose the Finish button). You might notice that the inserted legend doesn’t identify the feature type (roads, streams, ownership) for the legend symbols. We can change this by double clicking on the inserted legend, selecting the layer that we want to add information for in the items tab, and specifying what legend information we want to see: 1. Double click on the legend 2. Choose the Items tab 3. Click on Road Type in the Legend Items 4. Choose the Style button 5. Select “Horizontal with Layer Name, Heading, Label, and Description” Spatial Analysis of Forest Landscapes 66 6. Choose OK Follow the same procedure with the Streams and Ownership layer. Spatial Analysis of Forest Landscapes 67 Scale A scale is a necessary part of a map. Let’s try to add a scale bar by using the Scale Bar option under the Insert menu. You’ll be presented with a graphical display of many options. Select one by clicking on it with the mouse and choose OK. Spatial Analysis of Forest Landscapes 70 line, additional single clicks will establish changes in line direction (vertices), and a double click will end the line. Neatline A neat line is an important part of most maps and can be added by selecting Neatline from the insert menu. Select this option but be careful to click the Place around all elements option under placement. This will make sure that a neatline is drawn around all map elements. Your map should look similar to the graphic below. Spatial Analysis of Forest Landscapes 71 Legend Owl Nests Road Type Primary Highway (2-3 lanes) Secondary Highway (2-3 lanes) Dirt Road Paved USFS Road Gravel USFS Road Unimproved Road (4 wheel) Unknown Stream Type Perennial Intermittent Unknown Ownership BLM Private Siuslaw NF State 0 2 41 Kilometers ¯ Owl Nest Locations and Ownership Patterns Michael Wing Study Area Save your map document. Spatial Analysis of Forest Landscapes 72 LAB 2 Application: Mapping Forested Resources Create a three-panel thematic map showing the following information from the Stream Gauges data frame in lab2. mxd: 1. Stream gauges with stream classes and watersheds. 2. Stream gauges with road types and ownership classes. 3. Location of watershed area relative to Oregon’s border (make this a smaller inset map). You will need to create a separate data frame for each- it may be useful to label your data frames as you create. I highly recommend periodic saves of the project as your map document file as your work progresses. This map is due with your other lab 2 materials. Make sure that your map contains all author names.