This guide was created by the staff of the GIS/Data Center at Rice University and is to be used for individual educational purposes only. The steps outlined in this guide require access to ArcGIS Pro software and data that is available both online and at Fondren Library. |
The following text styles are used throughout the guide: Explanatory text appears in a regular font.
Folder and file names are in italics. Names of Programs, Windows, Panes, Views, or Buttons are Capitalized. 'Names of windows or entry fields are in single quotation marks.' "Text to be typed appears in double quotation marks." |
The following step-by-step instructions and screenshots are based on the Windows 7 operating system with the Windows Classic desktop theme and ArcGIS Pro 2.1.3 software. If your personal system configuration varies, you may experience minor differences from the instructions and screenshots. |
Before beginning the tutorial, you will copy all of the required tutorial data onto your Desktop. Option 1 is best if you are completing this tutorial in one of our short courses or from the GIS/Data Center and Option 2 is best if you are completing the tutorial from your own computer.
If you are completing this tutorial from a public computer in Fondren Library and are logged on using the gistrain profile, follow the instructions below:
If you are completing this tutorial from a personal computer, you will need to download the tutorial data online by following the instructions below:
The first set of data you will be working with contains the Houston Police Department (HPD) beat boundaries. Though it has been modified for the purposes of this tutorial, the original data was obtained from the City of Houston GIS Database webpage, which is no longer available, but the original data can be obtained from the GIS/Data Center data collection.
Notice that the police beats in the City of Houston have been divided into two separate feature classes covering the northern and southern portions of the city respectively. You will now examine their attribute tables.
Notice that you are provided with both the beat number and the district number for each police beat, and there are 55 beats in the north layer.
Notice that the south layer contains 62 beats with the same data fields.
At this point, you wish to combine the north and south police beats into a single layer. You will do so using a geoprocessing tool.
Notice that the Geoprocessing pane has opened on the right as a new tab on top of the Contents pane. Typically, you would use the 'Find Tools' search box to search for the name of the tool you'd like to use, but, at times, especially when learning the software, it can be helpful to view the full hierarchy of all the tools available, because you will often discover related and helpful tools that you didn't know existed and wouldn't know to search for. You might also completely forget the name of a tool, but be able to locate it based on the hierarchy. For these reasons, we will be manually navigating the toolboxes for this tutorial. The more typical workflow of searching directly for a specific tool will be covered briefly at the end of the tutorial.
Read the Merge pane help and review the sample illustration. Notice that this tool merges two like datasets covering different geographic extents together into a single dataset.
After selecting the HPDBeats_South layer, another drop-down window appears.
Notice that the when you hover over the Output dataset window, Output Dataset defaults to your default geodatabase (C:\Users\gistrain\Desktop\GeoprocessingTutorialData\HoustonSchoolsAndCrime\HoustonSchoolsAndCrime.gdb).
Usually, it takes a few moments for the tool to begin executing. While the tool is running, you will notice text with the name of the running tool in the bottom right corner of the Map Display, as shown below.
When the tool is finished running, you will see a box pop-up in the bottom right portion of your monitor with the name of the tool. A green checkmark indicates that the tool ran successfully.
Scroll down the attribute table and notice that the attributes for both the north and south beats feature classes were preserved and combined into a single table with 117 beats.
Since you now have all the beats contained in a single layer, you no longer need the separate layers for the north and south beats.
As explained in the tutorial introduction, the collaboration with the schools is going to be based on the police districts, not the police beats. At this point, your HPD layer only displays the police beat boundaries, but its attribute table does tell you the district number corresponding to each beat.
Scroll down the attribute table while observing the values in the District field. Notice that each district contains many beats. You will now dissolve the police beats based on this District field so that all beat boundaries within a single district will be dissolved into a single district boundary.
Read the Dissolve help and review the sample illustration. Notice that this tool dissolves boundaries based on common field values. In this case, you will dissolve the police beat boundaries based on common district values, resulting in a file showing only the larger district boundaries.
Notice that only the dissolve field, in this case the District field, was preserved. Because multiple beats were dissolved into each district, it is not possible to retain all of the attributes of each separate beat.
Since you only need to use the police districts, you may now remove the police beats layer.
Now you will examine the school district boundaries. Though it has been modified for the purposes of this tutorial, the original data can also be obtained online from the City of Houston GIS Database webpage at http://cohgis.houstontx.gov/cohgis2010/index.html[g2] within the administrative boundary dataset.
Notice that this feature class displays the boundary of the Houston Independent School District, which can be considered the study area boundary for this project. All of the other data layers you bring into your map document can be clipped to the study area boundary to reduce the size of the files you are working with, which will eliminate visual clutter and allow various processes to run more quickly. First, you will clip the police districts to the study area boundary.
Read the Clip pane help and review the sample illustration. Notice that this tool clips one dataset to the extent, or shape, of another dataset.
Notice that the resulting HPDDistricts_HISD layer maintains the police district boundaries, but limits the extent of the districts to the extent of the HISD boundary. You no long need the full police districts layer and may remove it.
You will now work with a dataset containing the locations of all violent crimes (including murder, rape, aggravated assault, and robbery) occurring in 2010, as reported by HPD. Though the data has been pre-processed for this tutorial, the original data tables can be obtained online from the Houston Police Department Crime Statistics webpage at http://www.houstontx.gov/police/cs/stats2.htm.
You will now clip the crime layer to the study area boundary to reduce the size of the dataset.
Notice that you are provided with the date and hour of the crime, the type of offense, the premise code, the number of offenses, and the approximate address. Since crimes are actually only reported by the block address range, not the exact street address, this address represents the midpoint of the block on which the crime was reported.
The final dataset you will work with contains the locations of all the elementary schools in HISD. Though it has been modified for the purposes of this tutorial, the original data can be obtained online from the Texas Education Agency School District Locator Data Download webpage at http://schoolsdata2-tea-texas.opendata.arcgis.com/
Notice that you are provided with the elementary school name, address, and grade range.
Now you will create a one-half mile buffer around each school, so that you will later be able to count the number of violent crimes occurring in 2010 within each buffer.
Notice that all three fields contained in the original schools point layer (school name, address, and grade range) have been preserved. In addition, a new field has been added stating the radius of the buffer in feet.
At this point, you can see all of the violent crime locations along with the half-mile school buffers, but much of the map is so densely covered with overlapping points that it becomes difficult to tell exactly how many points there are and to see the underlying school buffers. In addition, while you can see the spatial distribution of the points, you are not provided with any sort of useful summary of the data. Performing a spatial join will allow you to discover exactly how many violent crimes occurred within a half mile of each school in 2010.
The goal of performing a spatial join is to add a numeric field to the end of the school buffer attribute table that tells you how many crime points are contained within each school buffer.
The new layer should appear at the top of your Contents pane.
Since the newly joined buffer layer contains all of the same information as the original buffer layer, plus the new Join_Count and Sum fields, you no longer need the original buffer layer. Since your crime data has now3 been summarized, you no longer need the original crime points either.
You can now easily tell which schools have the largest number of violent crimes occurring within a half mile radius.
You now have an attribute table that tells you the number of violent crimes that occurred within one year within a half mile of each school, but you would also like to have a table that tells you in which police district each elementary school lies. To create this table, you will perform another spatial join to add the attributes of the police beat to the back of each school that lies inside it.
At this point, only the elementary school point locations and the police district boundaries should be visible.
Remember that, at this point, the attribute table only contains the school name, address, and grade range.
The new layer should appear at the top of your Contents pane.
Notice that the five schools do not have a district assigned to them. That is because those schools fall within HISD, but do not fall within the City of Houston police jurisdiction.
In this tutorial, you navigated to various geoprocessing tools directly through the Toolbox; however, it is likely that when you go to work on your own, you may not remember exactly where all those tools are located. As long as you can remember the name of the tool or what it does, you can find it using the search function.
Click on the first tool that says Buffer (Analysis Tools) to open the tool.