1 Geography 464 Professor Timothy Nyerges TA: Guilan Weng Winter 2012 Assignment 2 Preliminary Analysis 1. Introduction Before we can begin our GIS analysis we need to have the geodatabase developed in lab assignment 1. There is more to building a database than merely compiling data. Our research objective is to find a location for a new waste water facility; therefore, we will creatively generate new information from the available data. The new information that we generate will serve as empirical evidence to support a location recommendation. This is one way that empirically verifiable new geographical knowledge is produced. We encourage you to think about this process as you progress in this work. We are using data to create new information and the new information will serve as evidence in support of an argument that we have been asked to make. We have been asked to argue for a recommended location for this new facility. A good argument requires empirically verifiable knowledge and the new knowledge we produce will be used for making an intelligent location decision. This said, we encourage you to think about how data, information, evidence and knowledge can lead to greater wisdom –lead to a wise location decision. Towards this end, we are building a geodatabase so that we can systematically model the data and produce new information. We will create a value structure by generating criteria data sets with key thematic layers and feature classes. 1.1 Learning Objectives Substantive: understanding how and why new information comes to light when performing a preliminary analysis. Methodological: learning how a GIS analyst performs a preliminary analysis for site selection and understanding the work flow. Methodological: learning how to produce decision support artifacts to communicate the character of a preliminary analysis to a diverse audience. 1.2 Overview 1) These learning objectives will be achieved by conducting a preliminary analysis characterized by inclusionary and exclusionary screening based on the geodatabase you created in assignment 1. 2) You will produce tables, workflow diagrams and maps to communicate the values driving your analysis, the work process you used to conduct it and the spatial characteristics of the results. 3) You will synthesize the experience through short answer essay. Geography 464 Professor Timothy Nyerges TA: Guilan Weng 2 Winter 2012 1.3 Research Question: Which parcels in King County are appropriate for consideration and which parcels are not? 1.4 Deliverables 1) Graphical artifacts include: a simple thematic map that shows excluded and included parcels, a table that shows the value structure, and a workflow diagram. 2) Answers to the following four prompts (no more than two pages) a) In a short essay, explain what new information comes to light when performing a preliminary analysis. b) Describe the process of a preliminary analysis to accompany your workflow diagram. c) Describe the values and measured criteria associated with your geodatabase to accompany your table. d) We produced four artifacts: 1) an essay, 2) a workflow diagram, 3) a table and 4) a map. Decide which one best conveys the spatial distribution and discuss why. 1.5 What you will need Your personal geodatabase comprised of King County data. Read the the readings related to the lecture this week. The following processes will be accomplished here. Exclusionary screening of unsuitable parcels based on size of area. Buffered feature class based on inclusionary and exclusionary criteria will be created for all the data sets. Feature classes will be overlayed by type (school, street) to reduce processing. Feature classes will all be clipped to the project area. Feature classes will be combined into one inclusionary and exclusionary feature class. A suitability attribute will be added to the parcel feature class. 3 Geography 464 Professor Timothy Nyerges TA: Guilan Weng Winter 2012 2.0 Process (NOTE: You will be working with a number of files that you will have to keep straight, so it might be helpful to decide on a naming system for each output file that makes sense to you.) 1. Reduce the size of the parcel feature class by excluding parcels that are too small. The parcel feature class is approximately 150mbs and contains more than 500,000 records. We will reduce the size of the parcel feature class by exclude parcels that are less than ten. Managing and manipulating large files over the geography network can be problematic. For this reason we suggest moving the 150mbs parcel file to the C:\temp directory on your computer. This will make the process faster. You can discard the 150mbs parcel file after you have created the new layer. When working with large files, one *key* strategy in ArcMap 10 is to uncheck the layer in the table of contents (TOC) so that it does not draw. You do not need to see the parcels for this next step. Since the parcel layer has more than 500,000 polygons it takes a long time to draw. Don’t draw. Use the “select by attribute” tool to select parcels that are ten acres and larger. (if unfamiliar with this tool use the help menu to learn about it) Before you select the qualified parcels, you need to calculate the area of parcels. Open the attribute table of parcels. Add a field name SHAPE_area, with float as type. Right click the heading of the new field SHAPE_area, select calculate geometry. Select Area in property and then click ok. It might take a while since this is a big file. Once the calculation is done, you can conduct select by attribute based on thes shape area. After you have selected the parcels that are more than 10 acres, create a new layer of the selected parcels. (43,560 sq ft per acre). Choose Data -> export data to create a new feature class. Rename the new feature class “parceltenacre”. Remove the parcel shapefile. 2. Create buffers for the school feature class Geography 464 Professor Timothy Nyerges TA: Guilan Weng 4 Winter 2012 Add the school dataset to ArcMap. Buffer the school feature classe, save the results in your analysis folder, and give the buffered feature class a name that indicate it is buffered (e.g. schsitebuf and save it in your geodatabase in your student folder). A buffer distance of 500 feet is recommended. The buffer tool is in the analysis toolbox inside the proximity tools. ArcMap ArcToolbox Proximity Buffer 3. Extract primary street from street network Use the “select by attribute” tool to extract primary street from the street network. In order to achieve it, you have to read the metadata of King County street network and decide the “key” variable and the appropriate values for your selection. Once you have selected the primary streets, create a new layer of the selected streets by “export selected data”. Rename the new feature class as primarystreet and save it in your student folder. 4. Create buffers for the street feature class. Buffer the primary street feature class and give the resulting feature class a filename that indicates it is buffered. Set distance = 150 feet Name output feature class (to indicate it is a buffered feature class) and save it back into your folder. 5. Clip buffered primary street feature class to parceltenacre. The next operation will limit the area of the feature class by clipping the feature class to the parceltenacre. To extract a clip of the school feature class that is within the parceltenacre: ArcToolbox Analysis tool Extract Clip Select the Input Feature class, which will be the buffered street feature class. Select the clip feature class as parceltenacre Put the output feature class in the analysis folder and name it to indicate that it is both buffered and clipped (e.g. streetbuffclip). 6. Buffer the sewer coverage Unlike the school buffers, which are intended to exclude areas around the schools from consideration, the buffer around the sewers are intended to be included areas for consideration. Create a buffer around the sewers by using the buffer wizard to buffer the clipped sewer feature class. The buffer distance should be 1500 feet. Put the output feature class in the analysis folder. 7. Buffer the wetlands, landslides and park areas Geography 464 Professor Timothy Nyerges TA: Guilan Weng 5 Winter 2012 These areas are representative of sensitive areas or areas where there are geologic hazards and the buffers around them are intended to exclude areas from consideration. Use the buffer tool to create buffers around the three remaining layers. Use 500 ft for distance in each case, name the outputs appropriately, and save them back into your analysis folder. 8. Overlay the feature classes to create the final feature classes for analysis At this point you have six clipped, buffered feature classes: schools, streets, sewer, wetlands, landslides and parks. Now you want to create two layers: one has all the areas that you want to include in your sitting process (street and sewer buffers); and the other one has all the area you want exclude (buffers for landslides, parks, wetlands, and schools). Use the Union tool to create two feature classes: “inclusive” and “exclusive”. Union two feature classes at a time, until you have two feature classes (inclusive and exclusive) for all the buffers, clipped to parceltenacre. If the process takes too long, you might consider click individual layers to parceltenacre and then union them.