Office of Planning, Environment, & Realty (HEP)
Planning · Environment · Real Estate
http://gis.macrosysrt.net/ctpp2000/viewer.htm
SUBMITTED TO:
FHWA -USDOT
1200 New Jersey Avenue, SE
Washington, DC 20590
SUBMITTED BY:
MacroSys Research and Technology
888 17th Street, N.W., Suite 312
Washington, DC 20006
(Phone) 202-366-8927, (Fax) 202-955-6021
Appendix: CTPP 2000 Part 3 GIS-based Online Query Help
The Census Transportation Planning Package (CTPP) is a set of special tabulations from decennial census demographic surveys designed for transportation planners. Because of the large sample size, the data are reliable and accurate. It is the only Census product that summarizes data by place of work and tabulates the flow of workers between home and work. And it is the only source of information with summary tabulations available for traffic analysis zones (TAZ's) that have been defined by State and regional transportation agencies. CTPP2000 is a special tabulation of responses from households completing the 2000 Census long form.
The CTPP 2000 is divided into three parts:
The CTPP 2000 Part 3 data is currently available in two formats: (1) CDs in a proprietary ".ivt" format that can be ordered through the Bureau of Transportation Statistics (BTS) online Bookstore, and (2) files in .csv format that can be downloaded from the BTS TranStats webpage. In the first case, the proprietary .ivt format requires the installation of special software before a user can query and process the data. In the second case, a user must download and save the large-size data files onto a local machine before he or she can retrieve the needed data. Because the lowest (or basic) geographic units (Census Tract, TAZ, and Block Group) varied by county increased the complexity of the datasets and increased the difficulty of aggregating data over regions with differing basic geographic units. This increased complexity also makes it more difficult for users to extract the needed data quickly and in the format they need.
The objective of this project is to improve the accessibility to CTPP 2000 Part 3 data through developing a user-friendly web-based GIS application, CTPP Web-based Mapping and Query System, which would enable transportation planners to access CTPP 2000 Part 3 data at anytime and from anywhere; to easily select areas on a map, perform data queries for the selected areas, and display queried data in thematic maps and other map-based charts.
The CTPP Web-based Mapping and Query System takes full advantage of recent developments in both web technology and GIS technology to provide user-friendly dynamic spatial and non-spatial data services over the Internet, including map-aided geographic entity (place and area) selection, multi-dimensional data query, and advanced mapping and map-based charting. The technology selected for implementing the web-based GIS application is ArcIMS. ArcIMS is a web-map tool set extensively used in governments and industries for geospatial information service on Internet. ArcIMS has most of the tools and built-in functionalities needed for developing the functions specified for the CTPP Web-based Mapping and Query System. Java servlet, JSP, and the APIs are used to develop any functions that are necessary to the system but not available in or cannot be developed easily with ArcIMS.
The CTPP Web-based Mapping and Query System can be run on the Windows platform. Attribute data of CTPP are stored in MySQL database, and the supporting spatial data are stored in geo-database. All major components of the system, from web interface/application, to map server, to CTPP attribute database, to supporting geo-database, have been developed coordinately and integrally. At the same time, there is a high degree of modularization to allow each of the components to be updated and modified separately.
Based on the requirements from the project sponsor, the Federal Highway Administration (FHWA), the current version of the CTPP Web-based Mapping and Query System is developed to prove the concept of GIS-aided web data query and display and to allow users to access CTPP2000 Part 3 home-to-work flow data in the following tables (three out of the 14 tables of Part 3) for the three pilot states (Illinois, Indiana, and Wisconsin):
In addition, some extra functions have been developed to expand the utility of the application. These extra functions include Google Map API aided thematic map, route map, as well as expanding CTPP database with the home-to-work route distance and travel time data from Google Map service.
The most important feature of the CTPP Web-based Mapping and Query System is its user-friendly interface. This feature allows users to easily access all functions of the application based on intuitive logical flow. The interface integrates map and text selections to allow users to navigate smoothly in defining and executing their queries. With this feature, complicated queries are executed by simple clicks and users get all query results quickly and in the format they need, such as data tables with sorting function and downloadable CSV format, chart, thematic map and route map.
This feature allows users to retrieve multiple variables and improves the efficiency of data retrieving and extraction. More importantly, the query results can be presented on map to provide visual comparison and insights that could not be easily derived from data tables.
As mentioned above, the system provides many output options to allow users to view data, print data, download data, make charts online, create thematic and route maps. These options can be further extended based on customers' requirements.
The selection function allows a user to make selections on a map of the geographic entities of the CTPP data using various ArcIMS tools (see the Appendix for information on these tools). This selection function is applied to the following areas:
The order in which the Residence and Workplace areas are selected does not affect the result of a query.
As part of the selection function, the application also allows users to zoom in /zoom out over the supporting map and perform other basic GIS functions (such as to view legend, overview map, print the map, etc.).
The tabulation function allows users to generate tabular summaries of the following data for the selected areas.
The original CTPP 2000 Part 3 data are currently available only on a state-by-state basis. When combining multiple states into one database, duplicate records for the same origin-destination pairs that appear in both the origin state file and the destination state file must be eliminated to avoid double-counting. With the combined database, the tabulation function allows cross-state commuting data tables to be generated easily.
The mapping function allows users to produce the following maps.
The output function allows users to export the following output generated from the application:
The formats of the output files for query results are in CSV format. GIS data are in shape file format.
The development of this application employed many cutting-edge web and GIS technologies. Based on the experience gained in the process of this project, we recommend the following software and hardware to expand this application from a regional level to the national level that includes all regions of the United States.
ESRI ArcGIS server 9.3 with advanced functionality is recommended as the GIS software for implementing the CTPP Web-based Mapping and Query System at the U.S. national level.
ArcGIS has two important advantages over the ArcIMS, the GIS software used in developing this pilot Web-based Mapping and Query System.
Computer hardware
The pilot Web-based Mapping and Query System has been developed and is running on Windows system. We recommend use of Load Balanced Servers to host the Web-based Mapping and Query System at the national level.
MySQL has been used for this pilot project on the Windows system. The data size for the entire pilot project is about 4 GB. When expanded to the national level, the size of the combined database will be 80 to 100 GB. Even though MySQL can still handle the database at this size, the performance of the application may be severely impaired. Therefore, we recommend Oracle database for the Web-based Mapping and Query System at the national level.
Based on our experience with the pilot system, the large amount of data involved at the national level will present an overwhelming challenge to the performance of the new full-scale system and make it necessary to redesign and redevelop the existing functions in new ways. For example, the drop-down list function currently used to facilitate selections may not work anymore because the list will be too long and become unfriendly. Query results will more likely be suppressed because they contain too many records to be displayed at once by the web browser. Although we gained knowledge and experience through the pilot project about CTPP data and the functionality requirements for the system, the task to improve the performance of the system at the national level in terms of both speed and scalability will require a significant amount of research and testing.
NOTE: In order to maintain the performance of the application at a reasonable level, the maximum number of records of a query result to be displayed is set at 1,000. If a query generates more than 1,000 records, the query result will NOT be displayed in any form (table, chart and map). However, the query result can be downloaded directly onto the user's local PC.
The primary purpose of the CTPP 2000 GIS-Based Online Query Application is to make the query of the Journey to Work related data in the CTPP 2000 database easy, intuitive, and with visual aids. While there are many ways to achieve the same results, a query in the application always involves three major sequential steps.
Step One - Select Residence and Work Areas for a query.
Step Two - Decide the information to be queried from a CTPP table.
Step Three - Decide how to display the query result.
The application offers two tools to assist the user to select Residence and Work Areas for a query. One is Text Selection, which is a conventional dynamic web interface that allows the user to decide the level of geography (State, County, County Subdivision, Census Tract, etc.) for the query, select Residence and Work Areas of interest, and select the data to be queried (the CTPP 2000 tables and variables). This interface is dynamic because Residence and Work Areas available for selection are dynamicly decided by the user's selection of the level of geography.
The other tool is Map Selection, which is a GIS-aided dynamic interface and allows the user to select Residence and Work Areas of interest directly from a map. With this tool, the user starts a query by deciding the level of geography (State, County, County Subdivision, Census Tract, etc) for the query and by selecting a "Selection Tool" from the GIS Tool Bar of the interface (by a single click on the tool) to be used for selecting. Once these two decisions are made, the user can select (and reselect) the Residence and Work Areas of interest by clicking and dragging on the map.
After selecting the level of geography for the query, the user can select Residence and Work Areas in any order. Only the current selections will be used to display the query result. Once the Residence and Work Areas are selected, the user can go to "Variables Selection" page to finish up the query process and decide how to display the query result.
The more familiar the user is with the GIS Tools, the more effectively the user can take advantages of the Map Selection. The following table presents information on how to use each of the available GIS Tools.
Icon |
Tool Name |
Function |
|---|---|---|
Show Legend |
A single click on this icon to show map legend in a new window. |
|
Zoom In |
When this icon is selected, clicks on the map will "zoom in" the map view, centered on the clicked position. |
|
Zoom Out |
When this icon is selected, clicks on the map will "zoom out" the map view, centered on the clicked position. |
|
Zoom to Full Extent |
When this icon is selected, a click on the map will zoom the map view to the full geographic extent of all layers combined. |
|
Zoom to Active Extent |
When this icon is selected, a click on the map will zoom the map view to the full geographic extent of the active layer. |
|
Zoom to Last Extent |
Clicks on this icon will toggle between the current extent of the map view and the previous extent. |
|
Pan |
When this icon is selected, left-click on the map and hold to drag the map around to show different parts of the map on the screen. This tool is particularly useful when the extent of the map is larger than the computer screen. |
|
Query |
A click on this icon will bring up a user interface at the bottom of the map view to allow the user to construct queries about the active layer. To construct a query:
|
|
Find |
A click on this icon will bring up a user interface at the bottom of the map view to allow the user to find a specific string of text in the underlying data of the active layer. |
|
Select by Buffer |
When a selection (either a point or an area) has been made on the map, a click on this icon will bring up a user interface at the bottom of the map view to allow the user to create a buffer on the map around the selection according to the parameters provided through the user interface by the user. At the user interface, if the "Display Attributes" option is selected, "Create Buffer" will also display the data/information available for the selected areas and points in a table at the bottom of the map view. |
|
Select by Circle |
When this icon is selected, the user can select the geographic areas of the active layer by drawing a circle on the map. The center of the circle is determined by a single left-click on the map and the radius of the circle is specified by the user through the user interface which would show up at the bottom of the map view when the "Select by Circle" icon is selected. All geographic areas touched by the circle will be selected. Selected areas are highlighted, and data/information available for the selected areas are displayed in a table at the bottom of the map view. |
|
Select by Line or Polygon |
When this icon is selected, the user can select the geographic areas of the active layer by drawing a line or a polygon. A line or a polygon can be drawn by left-clicking on the map and then clicking on the "Complete Line & Select" or the "Complete Polygon & Select" button in the user interface at the bottom of the map view. The user interface appears when the "Select by Line or Polygon" icon is selected. All geographic areas touched by the line or polygon will be selected. Selected areas are highlighted, and data/information available for selected areas are displayed in a table at the bottom of the map view. |
|
Select by Point |
When this icon is selected, the user can select the non-adjacent geographic areas of the active layer one-by-one by left-clicking on them on the map. The user can also select a group of adjacent geographic areas by left-clicking (and holding) and dragging to create a rectangle. All geographic areas touched by the rectangle will be selected. Selected areas are highlighted, and data/information available for selected areas are displayed in a table at the bottom of the map view. |
|
Clear Selection |
A click on the icon will clear current selection(s) from the map. However, it will not clear the list of geographic areas that have been selected for the query. |
|
Click on this icon to create a printer-ready page of the current map view on the screen and its legend with preformatted map layout. Enter a title for the map through the Title Box at the bottom of the map view and click on the Create button to create the printer-ready page. Use your browser's print function to print the map. |
||
Overview Map |
Click on this icon to toggle on and off the overview map. This tool helps the user to see the location of "zoom in" area on the map. The user can also move the red box within the Overview Map to show different areas in the map view window. |
|
View/Refresh the Selected Areas |
Click on this icon will zoom the map view to the optimal extent to allow the user to view all the selected area at once. It will also refresh the list of the selected areas in the left-side bars if any selected areas have been removed from the selection. |
|
|
Deselect Selected Areas |
Click on this icon will deselect all selected areas from the map and clear the list of selected areas in the left-side bars. |
