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CommunityViewer GIS & Viewing Geocodes Street Segment Attributes Finding all Street Segments Geocoding an Address File Q&A: Using TLFGeocoder |
TLFGeocoder
-- geocoding software companion to CommunityViewer View your address data in maps. See how your addresses are distributed in the context of other data. Use TLFGeocoder to convert your address data into map file format and add geocodes so that your data can be aggregated to geographic areas of interest to you. The TLFGeocoder (TIGER/Line File Geocoder) is an address look-up, street analysis, and geocoding program developed by Proximity. This section provides an overview of TLFGeocoder features and a step-by-step tutorial showing how to use the TLFGeocoder. A unique feature of TLFGeocoder is its ability to access and use no fee Census Bureau TIGER/Line files. The TIGER/Line files (TLFs) are used directly by TLFGeocoder to geocode and otherwise process addresses, streets, and address data using the TLF data as the 'geographic base file.' Augmented versions of TLFs, having updated or extended coverage data, may also be used by TLFGeocoder. TLFGeocoder also performs geocoding operations using the TIGER streets shapefiles. In the fall of 2007, the Census Bureau will release the new TIGER shapefiles. Use TLFGeocoder with legacy TIGER/Line files, streets shapefiles from Proximity, or the TIGER streets shapefiles. Census 2010 and LUCA. While the Census Bureau plans to provide software to support some needs associated with the Census 2010 Local Update of Census Addresses program, the software does not provide for geocoding of local addresses. TLFGeocoder can be used to meet this need. Geocode your address data and have TLFG insert the geocodes and create an address point shapefile. You are then ready to use that address point shapefile with CommunityViewer to view Census supplied data. Download TIGER/Line Files. Download and expand the TLFs for your area of interest via the Census Web server. TLFGeocoder may be used with single county TLFs (alternatively, use of streets shapefiles can be for any area covered by the shapefiles). Only TLF file types RT1, RT2, RTA, RTC, and RTZ are required. Expand all of the TLF record types if you prefer or just the selected types to conserve disk space. Getting Started. Start TLFGeocoder. Use the Open File button to open a TIGER/Line file (or streets shapefile). The TIGER/Line files for Alexandria, VA are included with the TLFG setup. Streets display in the map window, layer names are shown at left in the legend panel. The geocoding panel is shown at the right of the screen. 
Optionally use the AddLayer button to add a shapefile, such as Virginia by county, to give more definition and assist with navigation. The name of the layer is added to the legend panel. State by county boundary files may be downloaded here and added to the view. 
Finding One Address. The default address is 2601 Cameron Mills Road which is known to exist in Alexandria. To locate this address, click the "Find First" button. The result, shown below, displays the first instance of a Find. The map shows a zoom-in to the line segment which highlights in red. The address location is shown as a yellow marker. A profile of the matched street segment appears in the list box to the right. A profile of any street segment may be viewed by selecting the Identify tool (button), making the streets layer active (click once on the layer name in the legend panel), and then click on the street segment of interest. 
Street Segment Attributes/Fields. Street segment attributes are shown by field name (see above view). Field name descriptions are shown below.
Rules for Entering an Address. Click on the "Help" button to view syntax and additional tips for entering an address for look-up. A partial display of that information is shown below. Not all of the fields are mandatory. For example, the ZIP code may be omitted. But if the same address exists in two ZIP code areas in the TLF (geographic base file), a "Find First" operation may locate the address in a ZIP code area that you did not have in mind or know to exist. 
Finding All Matching Segments. To locate route-oriented information, in the event the exact address is not known for example, use the Find All button. Key in the main portion where matches are sought and click "Find All". The following display shows the result of the Find All for "King St". Note that "King" alone might yield a different set of segments. 
Geocoding an Address File. Most geocoding involves processing a file of addresses. Each address is a record and there might be thousands of address records in a file. To geocode a file of address-related records using TLFGeocoder, an address file is needed. This version of TLFGeocoder requires the address file to be structured as a dbase 4 file (see details on address dbase file below). 1. Use the Open Addr button to open the address file to be geocoded. -- c:\tlfgeocoder\alexaddr.dbf is included in the setup 2. Use the New Shape button to name the new point shapefile to be created. -- use any new shapefile name like c:\tlfgeocoder\newshp1.shp 3. Click Geocode to start geocoding. Geocoding then proceeds. If the Pause checkbox is checked, the matching will pause and wait for reply as each address is matched. This option provides a way to view where each address geocoded is located in a map view. 
As the geocoding occurs, the matched location is shown in the map view. At the same time, the address file record is updated and geocoding results are added to each record. Zoom in for a closer view. Use the Layer Editor (dbl-click layer name) to add labels. 
In this example, the address file is named alexaddr.dbf. The file is a dbase file. The following view shows contents of the file opened using Excel. 
The address file is structured in the following manner: 
The fields addr1, zip5, lat, lon, and geoid are required. They may exist in any order. The file must be a generic dbase 3 or 4 file. The fields, lat, lon, and geoid are created as the file is geocoded. Excel can be used to create the file in dbase 4 structure. Even though this might seem straight-forward, it can be tricky. Follow these steps.
Using TLFGeocoder, the process generates the latitude and longitude for each address and places them in the address record (effectively updating the address record). GEOID defines the geocode location of the line segment associated census block. For example, the value of GEOID added into the address record for Charles Barrett School shows that the address is located in State FIPS code 51, county FIPS code 510, census tract 201000, and census block 1009. The latitude-longitude fields added by geocoding process show that the school is located at the point -77.076900 degrees longitude and 38.841650 degrees latitude. Using GEOID, it is possible to associate this address with corresponding school district, zip code tabulation area, and many other areas using the Proximity C2KBLK database. Address Matching and Geocoding. In general, geocoding is the process used to locate an address on a map and/or assign geographic codes (geocodes) to one or many addresses. TLFGeocoder does both. Geocoding responds to the need for users who need a census tract code for address(es) for compliance reporting. By using geocoding, the school district containing the address can be determined. By geocoding client addresses, the clients may be viewed as icons on maps and in other pattern recognition operations. These are a few examples of benefits from and uses of geocoding. Benefits and Uses of TLFGeocoder. TLFGeocoder fills the need for a no cost geocoder that can be used directly with the Census Bureau TIGER/Line files. Most geocoding software requires that the TIGER/Line files be converted to a different structure, often involving costs, time, and special expertise, before the TLFs can be used for geocoding. TLFGeocoder requires no conversion and has a minimal learning curve. For users with more advanced requirements, other versions of the TLFGeocoder are available. Contact Proximity with questions or to describe special requirements. Q & A - Using TLFGeocoder Q. Why use TLFGeocoder to find an address? I could just use a Web-based address finder. A. These tools cannot tell you what school district (or many other types of areas) where the addresses of interest are located. TLFGeocoder does this for you. In addition, these tools cannot take a set of addresses, obtain the corresponding latitude-longitude and geocodes and place in a file for viewing with a GIS. TLFGeocoder does this for you. Also, for many operations, you might need to see the geographic codes for areas on each side of the street where an address is located (such as the city). These tools cannot provide this information. TLFGeocoder does this for you. Q. Is a version of the software available that operates in a batch environment? A. Yes. A "silent" version of TLFGeocoder exists that may be executed from a Run command or called by another program. The program is started with a set of parameter values rather than entering the values via a graphical user interface. Q. My address range covers more than one county. What are options to meet this need? A. TLFs may be appended. However, this can be an error prone process. The standard and professional versions of the Geocoder provide TLF management utilities to compress space required and make merger of even very large multi-county areas easier. Q. Are there features of TLFGeocoder not available in ArcView? A. Yes. Since TLFGeocoder does not require a "streets shapefile," developing or acquiring such files can be avoided. Streets shapefiles are not available from the Census Bureau. Unlike ArcView, TLFGeocoder places the latitude-longitude codes, and the "primary geocode sequence" (coding to the census block level), in an updated address record. As a result, these fields are directly accessible for follow-on applications using other software. Additional Information Proximity develops geodemographic-economic data and analytical tools and helps organizations knit together and use diverse data in a decision-making and analytical framework. We develop custom demographic/economic estimates and projections, develop geographic and geocoded address files, and assist with impact and geospatial analyses. Wide-ranging organizations use our tools (software, data, methodologies) to analyze their own data integrated with other data. Contact Proximity (888-364-7656) with questions about data covered in this section or to discuss custom estimates, projections or analyses for your areas of interest. |
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