Census Bureau

TIGER/Line® 1995

Background

The TIGER/Line® '95 county files were produced from the TIGER data base from late Summer 1995 to early Spring 1996, with most of the files produced in 1996. The principal reason for the release of TIGER/Line® '95 is to correct a problem found in some files of the TIGER/Line Files®'94. The problem is that a partial or blank block number may appear on one side of Record Types 1 and 3 even though the block number appears correctly on the related Record Types A and S. This problem affects those geographic information systems (GIS) that rely on the linear geographic entity codes rather than the polygon geographic entity codes. The exact files that may be affected are not known, but the maximum extent of affected files is limited to the 369 counties whose files meet the processing criteria for containing a possible mistake. There is a list of these counties and some additional information on the problem in TIGER/Line®'94 User Note 2 stored on this site.

The TIGER/Line® 1995 CD-ROMs do not contain software to display or generate maps, nor are these data stored in the form of graphic map images. To create maps with these TIGER/Line® data, one would typically use a Geographic Information System package or other mapping software. For information on how to use these TIGER/Line® data with a specific package one should contact the company that produced the package. For information on companies that sell products that use TIGER/Line® data or that provide various TIGER/Line®-related services refer to the "Vendor List" on the TIGER Page at the Census Bureau's World Wide Web site described below.

New Datum

Aside from the corrections noted above, the principal difference between the 1994 and 1995 versions is that the coordinates, for most areas, are now based on the 1983 North American Datum (NAD83). The exceptions are Hawaii and the Insular Areas of the Pacific which remain on the local datums used for earlier versions of TIGER/Line® . This means that the latitude and longitude for the features in TIGER® are likely to shift to some degree from what they were in the earlier versions of TIGER®.

A datum is the term used for the reference point or origin for all the measurements (horizontal and vertical) on which precision maps are based. Since the earth is not a true sphere, we need an accurate understanding of its exact shape in order to accurately plot the locations of features using a reference system such as latitude and longitude. Over the years scientists have developed more accurate mathematical models to represent this shape (called an oblate spheroid) as their techniques and instruments have improved. The most recently adopted datum ( NAD83) is based on our understanding of the earth's shape resulting from improvements in measurement precision derived from the use of satellite tracking data. The original source materials from which TIGER® was derived (principally US Geological Survey topographic maps) were in NAD27. To keep in step with other national mapping programs the Census Bureau has moved to the new standard.

We converted these TIGER/Line® data from NAD27 to NAD83 using the PC-based software package NADCON available from the National Geodetic Survey (NGS). If you have a data set that you would like to convert from NAD27 to NAD83 the software is available for down loading from the NGS Web site. Once at the site, follow the links for NGS Products to the PC Products page where NADCON is listed.

Other Improvements

We have made limited improvements in address range and feature coverage between the 1994 and 1995 versions. Any improvements were done as a result of the various cooperative programs we have with local officials such as the TIGER Improvement Program and the 1995 Boundary and Annexation Survey as well as special censuses. Since the scope of these improvements is scattered it is difficult to categorize it for the potential users of this release. However, we are exploring ways to develop such information and may be able to provide it in the future.

Version Code

TIGER/Line® '95 has version code 0024, uses the file suffixes "bwn", where "n" is the record type. For further information you may down load the TIGER/Line® '95 documentation.

Distribution

TIGER/Line® '95 is being distributed in essentially the same manner as the 1994 version. There are six CD-ROMS with the same grouping of states and other areas. One innovation in the documentation is that we are providing it in PDF format which is readable by the ADOBE Acrobat reader. Versions of the reader for PC-compatable computers are included on the CD-ROM. For other platforms, versions are available from ADOBE and information on where to download them is available on this site at the TIGER/Line® '95 documentation page referenced above.

The price will be the same as that for the TIGER/Line® '94 which was $250 per CD-ROM and $1500 for the complete set. To place an order for TIGER/Line® '95 call our customer service office at 301-457-4100 or visit the Market Place page on our Web site.

SPECIAL NOTE FOR PREVIOUS PURCHASERS OF TIGER/Line® '94 - For those people who purchased TIGER/Line® '94 from the Census Bureau or received it directly from the Bureau of Transportation Statistics (BTS) US Department of Transportation we will be providing a free copy of the appropriate 1995 version disk(s). Using the information from the Census Bureau's customer list and information provided to us by the BTS we will mail the disks to you. We will begin sending out the replacements during the week of September 30 and you should receive them by the end of October at the latest.


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  Last Revised: Monday, 17-Mar-97 12:48:34