|11.520: A Workshop on Geographic Information Systems|
|11.188: Urban Planning and Social Science Laboratory|
For this test, we will use datasets, in the class data locker, from past homework and labs plus a new shapefile, a new data table, and a new grid coverage. All shapefiles and grids represent location using Massachusetts State Plane coordinates (NAD83) in meters. The old datasets are in the class data locker and the new datasets sets are in M:\test07data. (which is the same location as http://mit.edu/11.520/data) Here's a summary of the datasets you will use
Full pathname Description M:\data\MATOWN00.shp Shapefile from MassGIS of political boundaries for the 351 Mass municipalities. This is the shapefile in the class data locker that we have already used in several exercises. An updated version of this shapefile is available at: http://www.mass.gov/mgis/towns.htm M:\test09data\EXITS_PT.shp Shapefile of points from MassGIS, that mark the location of all exits on limited-access highways (i.e., interstates and certain major State roads) in Mass. Attributes include exit number and Route number. See http://www.mass.gov/mgis/exits_rtes.htm for further detail. M:\test09data\ParknRideLots.shp Shapefile of park-and-ride lot locations from MassDOT, via MassGIS. Attributes include Capacity = number of parking spaces, Status, and yes/no/maybe (Y/N/?) answers regarding whether the lot has bike racks, lights, boat_service, rail_services, etc. The shapefile was developed from a MassDOT GeoDatabase downloaded from the MassGIS website: http://www.mass.gov/mgis/eot_layers.htm M:\test09data\LOTCAP2.DBF A dBase (dbf) formatted table for the 60 park-and-ride lots in the ParknRideLots shapefile that are operational and have known capacity. The OBJECTID, CAPACITY1, AND STATUS columns are the same as in ParknRideLots (with capacity1 being the original 'capacity' attribute). The CAPACITY2 column is the same as CAPACITY1 but expressed as an integer instead of as text. M:\test09data\madoreqv.dbf A dBase-formatted table containing data about the 351Mass cities and towns developed from the 'Comparison Criteria Report' published annually by the Mass Dept. of Revenue (DOR). These data are from the year 2004 report and include these fields: town name (Municipali), county code (county_cod), 2002 population (pop02), 1999 per capita income (inc99), assessed property value per capita (eqv2002), area in square miles (sqmi), road miles as of 2002 (roadmile02), fiscal year 2004 municipal budget (budget04), and number of parcels as of 2004 (parcel04).
An ArcGIS grid coverage that was developed by rasterizing the matown00 shapefile using 1km grid cells. The attribute value for the grid is the distance in meters from the center of each grid cell to the nearest major highway exit (in exits_pt).
Before starting to use these datasets, you should copy the entire 'test09data' directory to a local drive (C:\usertemp in Room 37-312 and C:\temp in Room 9-251.) Using the data from your local drive will speed up the processing and ensure that you have write access to the files - just be sure to copy the whole directory back to your network locker (drive I) before you leave! Once you have copied the test09data directory to a local drive, run the ArcMap document, test09_start.mxd that is in the directory. This ArcMap document will load all the new shapefiles and tables that you need (except for the matown00 shapefile that will have the wrong source location and you will have to reset the source or remove that shapefile and get a fresh copy from the data locker (./data/matown00.shp).
Using the ParknRideLots shapefile, answer the following questions about park-and-ride lots in Massachusetts::
The ParknRideLots shapefile has an attribute field CAPACITY indicating the number of parking spaces available in each lot. However, this field is coded as text (with '?' indicating a missing value). For your convenience, we have prepared a separate table that converts this attribute into an integer for the 60 operational lots with a known capacity. This table, LOTCAP2.DBF, can be joined to the original ParknRideLots attribute table using the OBJECTID field.
Using the ParknRideLots shapefile and the LOTCAP2.DBF table, answer the following questions regarding the 60 park-and-ride lots whose capacity is known:
Add the exits_pt shapefile to your ArcMap session and answer the following questions:
Part II-1A (10 points [5+3+2): How many municipalities have at least 10 miles of roads (roadmiles02) per square mile of area? _____46_______ Which municipality has the highest density of roads? ___Somerville______ What is the road density for that municipality? ____25.7 linear road miles per square mile of area_________
Part II-1B (22 points): Develop a thematic map showing the density of road miles within each municipality (roadmiles02 / sqmi). Turn in a PDF version of a properly annotated ArcMap layout of this thematic map using quantile classification with 10 categories. Display the major highway exits on top of the thematic map and show a 2 km buffer around the highway exits. Use a 50% transparency factor for the 2-km buffer so that the town boundaries and thematic shading are partly visible through the buffer areas. Also, include on your map, a symbol indicating the location of those park-and-ride lots that are operational and have known capacity (using the ParknRideLots shapefile and LOTCAP2 table). Make the size of the symbol proportional to the capacity of the lot. (Hint: In case you aren't familiar with setting the transparency level for the buffer, you can set it from the display tab of the 'layer properties' window).
Sample Map #1: (click map to enlarge)
Sample Map #2: (click map to enlarge)
Note that Map #1 used 'proportional symbols' rather than 'graduated symbols' for the symbol of the park-and-ride lots so the 'long tail' with a few very large lots is more evident. Map #2 uses 'graduate symbols,' which also earned full credit). The main point is to use the symbol to show the relative size of the lots. Map #2 also used a grayscale color scheme for the road density shading so the foreground of exits, exit buffers, and lots is more prominent. Both maps are slight variations of those submitted by two students.
Part II-1D (5 points): Explain briefly a few pluses and minuses of using equal interval vs. quantile classification to visualize the spatial distribution of road density among the 351 Massachusetts municipalities.
There is no single correct answer. Here are some key issues:
- Pluses: Each category covers the same data range, and reflects the absolute values of the data;
- Minuses: When data are not evenly distributed, some categories may include most of the data, and some categories may have no data, which make the map hard to read and interpret.
- Pluses: Each category covers the same number of cases, and relfects the relative values of the data when compared with other data. Hence, the map is easy to interpret to identify places that are relatively high, medium, low..
- Minuses: The data in different categories may have small value differences.
For this question, we will examine the proximity of park-and-ride lots to major highway exits.
Part II-2A (5 points): Determine the distance from each of the 60 operational park-and-ride lots with known capacity to the nearest major highway exit. For this question, you'll want to use the 'Near' tool within the Proximity portion of the Analysis Tools in ArcToolbox. (Note that the 'near' tool will not work if the input feature shapefile is joined to another table. You will need to remove any joins or export the shapefile with the join into a new shapefile.) Determine which park-and-ride lot is the furthest away from any of the major highway exits? Name the town containing the lot: ___Falmouth________ What is the distance from that lot to the nearest major highway exit: _____21.14 km_______
Part II-2B (5 points): Next, we would like to examine the average distance to the nearest exit for lots that are operated by different authorities (as indicated by the name in the attribute field OPERATOR. Summarize the results of your 'Near' calculation by generating a table that has one row for each type of OPERATOR of the 60 operational park-and-ride lots with a known capacity. Include in the table a column indicating the number of lots in each category, the total number of parking spots (i.e., the sum of the capacities), and the average distance-to-the-nearest-exit for the lots in each category. Turn in an electronic copy of this table sorted by the average distance (a screenshot of the table is sufficient).
For this question, you will need the matown00 shapefile, the madoreqv table, and a grid coverage ExitDis_gd that rasterizes the matowns00 shapefile into 1km grid cells and contains, as grid cell values, the distance from each grid cell to the nearest major highway exit. (The computation was done using the 'euclidean distance' tool in ArcToolbox. equal to the using 1 km grid cells.)
Part II-3A (4 points): There are 10 municipalities in Mass that have fewer than 1.5 miles of roads per square mile of area (roadmiles02 / sqmi). None of these 10 municipalities has a major highway exit within its boarders. How many polygons are used to represent these 10 towns in the matown00 shapefile? ___26____
Part II-3B (4 points): We would like to determine which of these 10 municipalities without a major highway exit is closest to an exit. The ExitDis_gd grid coverage has the relevant distance values. Let's define what we mean by 'closest' to be the average (viz. the mean) of the distance-to-exit values across all grid cells centered in the town. Use the zonal statistics command from the Spatial Analyst toolbar or the 'zonal statistics as table' tool in the 'spatial analyst tools' section of ArcToolbox to compute this average. Which of the 10 municipalities has the smallest average distance to major highway exit? __TYRINGHAM___ What is the mean value of 'distance to major highway exit' for this municipality? ____6942.67m____
Back to the 11.520 Home Page.
Back to the CRN Home Page.