III. THINGS TO KNOW ABOUT THESE FILES Data users should find the following information helpful before using the 1990 Census TIGER/Line files. TIGER/LINE CENSUS FILES, 1990 INFORMATION LIMITATIONS The information presented in this file is provided for the purpose of statistical analysis only. It is only a graphic representation of ground truth. The positional accuracy of the information is no greater than the established National Map Accuracy standards for 1:100,000-scale maps from the U.S. Geological Survey; thus, it is not suitable for high-precision measurement applications such as engineering problems, property transfers, or other uses that might require highly accurate measurements of the earth's surface. While the Census Bureau has made a reasonable and systematic attempt to gather the most recent information available about the features that this file portrays, the Census Bureau cautions users that the files are no more complete than the source documents used in their compilation, the vintage of those source documents, and the translation of the information on those source documents. The Census Bureau added to the TIGER/Line files enumerator updates that enumerators annotated on the map sheets prepared from the TIGER data base as they attempted to traverse every street feature shown on the 1990 census map sheets; the Bureau also made other corrections and updates to the map sheets supplied by local participants in Census Bureau programs. The locational accuracy is of dubious quality. The feature network of lines (as represented by Record Types 1 and 2) is complete for census purposes. Data users should be aware that they will not be able to trace a specific feature by name or by census feature class code as a continuous line throughout the TIGER/Line file. For example, State Highway 32 may cross the entire county. There will be line segments in the file at the location of State Highway 32 but the line segments may individually have such names as S. Elm Street, Smallville Highway, or State Highway 32. The most frequent census feature class code for a state highway is A21, but the line segments at the location of State Highway 32 may have class codes of A01, A40, or A21. The names of line features have been improved since the release of the Precensus version of the TIGER/Line files. Longer names that previously may have been truncated have been expanded to the full field width available in TIGER/Line. In addition, feature types, such River or State Highway, have been added or enhanced to clarify, for data users, the nature of the feature by giving the most complete name available from the TIGER files. Data users who are familiar with the Precensus version of the TIGER/Line files may wish to use the longer, more complete names given in the Initial Voting district codes and the 1990 Census versions. In addition to the Federal, State and local sources, these files may contain information obtained in part from the companies listed in Appendix B. Appendix B lists the State and county codes ("STCO"), the name of the source ("SOURCE MATERIAL"), and the name and location of the company (COMPANY/CITY/STATE/ZIP). The Census Bureau gratefully acknowledges the use of these materials in the initial building of the data base. Boundaries, ADDRESS Ranges, and GEOGRAPHIC AREA Codes The 1990 Census TIGER/Line files contain boundaries of legal areas as reported to the Census Bureau to be legally in effect on January 1, 1990, and the final 1990 census tabulation geographic area codes for those entities and certain statistical areas, such as blocks, census tracts, and block numbering areas. Address Ranges in the TIGER/Line File The TIGER/Line files contain potential address ranges only for selected urban areas. The address ranges in the TIGER/Line files originated with the address ranges contained in the 1980 GBF/DIME-Files. The conversion of this information to the TIGER format involved neither any verification of the previously existing address ranges nor any significant updates or corrections (except as noted below); in most cases, the address ranges for an area are the same as those in the corresponding 1980 GBF/DIME-File. Preparations for the 1990 census involved making some minor updates in selected areas, but generally did not include changes in address numbering systems during the decade nor the addition of address ranges for new features added to the files. Users of the TIGER/Line file address ranges should check for address range overlaps, gaps, odd/even reversals, and other situations that may be incorrect. Although an address range in the TIGER/Line file may be incorrect, the Census Bureau implemented procedures to ensure that the error did not adversely affect the accuracy or the quality of the 1990 census. For the geographic areas where the TIGER/Line file includes address ranges, the Census Bureau used the address ranges to perform an initial assignment of residential addresses (purchased from a commercial vendor) to these 1990 census tract and block numbers. Subsequently, field operations used enumerators to update, verify, and correct, when necessary, the list of addresses assigned to each block number by walking the perimeter and all interior streets of each block. The TIGER/Line file does not include any corrections to the address ranges resulting from the field operations because the address list exists independently from the TIGER data base. When a new feature was added to the TIGER data base and it split an existing street feature into two segments, the computer program "imputed" the point at which the existing address range should be split and assigned two "imputed" address ranges to the split segments of the street feature. When this situation occurred, a flag was set in the file (imputed address flag). Block Number After insertion of the results of the January 1, 1990 Boundary and Annexation Survey, the Census Bureau assigned an alphabetic suffix to the 3-digit block number ("collection" block number) for those blocks in which a tabulation boundary divided the collection block. We refer to the block number with the block number suffix (or blank if no suffix exists) as the "tabulation" block number. The final tabulation block numbers appear in the 1990 Census TIGER/Line files. A 3-digit block number that ends with "99" signifies water area. As there is only one "water block designator" (i.e., "99") within a block group, many water polygons can have the same block number. Water blocks do not appear in the 1990 census data files. Census maps and data files do not display the block number for water areas. The principal purpose for census block numbers for water areas is to identify all area and to allocate the water area to a geographic or governmental unit. Water blocks with the same 3-character basic block number or 4-character suffixed block number may not be contiguous to each other, but the water blocks will be in the same geographic or governmental unit. The TIGER/Line files may contain 1980 block numbers for portions of the country where the Census Bureau did not tabulate 1980 census data by block or block group. These situations occur because these portions of the TIGER file originated from the 1980 GBF/DIME-Files that extended beyond the 1980 block-numbered area. Data users concerned about the validity of 1980 block numbers are advised to discard all 1980 block numbers that do not correspond to block numbers in the 1980 MARF or 1980 STF files. Census Block Number Suffixes An alphabetic suffix may be appended to the basic census block number. In the case of land blocks, the alphabetic suffix will be upper-case letters, A through Y. In the case of water blocks, the alphabetic suffix will be upper and lower case letters, A through Y and a through y. All parts of a block may not be contiguous, but all parts of a block will be in the same geographic or governmental unit. Census Tract/Block Numbering Areas If the boundaries of counties and their statistical equivalents were revised, the Census Bureau had to change any affected census tracts and block numbering areas (BNAs) so that they would continue to nest within their appropriate counties. In addition, the Census Bureau has corrected the boundaries of some census tracts and BNAs in the TIGER data base based on information received from the participants in the 1990 census tract and BNA delineation programs. The Census Bureau made these changes after the release of the Precensus TIGER/Line files. The Census Bureau identifies the revised census tracts and BNAs with the unique number suffix of .98 (e.g., 1234.98) so that the data users can easily determine which census tracts and BNAs have been adjusted because of changes in county boundaries as of January 1, 1990 or at the request of local Census Statistical Areas Committees. If a census tract/BNA required additional suffixes, the next highest suffixes (i.e., .97, .96, etc.) were used. Crews of Vessels Crews of vessels represent a population on board both military (including Coast Guard) and civilian ships. (They do not include the inhabitants of a marina.) The census population tables show the vessels' population in a unique census tract/block numbering area and unique census block. The unique census tract/block numbering area code uses the same basic census tract/BNA number as the nearby land census tract/BNA plus a suffix of 99 shown in decimal notation; for example, 1234.99. The unique census block code uses the same basic block number as the nearby land block plus a block suffix of Z; for example, 901Z. In such a situation, the related land block also is assigned a suffix, even though it is not split by a boundary; for example, 901A, even though there is no 901B.) The Z census block suffix will not be used for any purpose other than crews of vessels. For TIGER/Line files, in record type 1, either the left or right census tract/block numbering area and the census block will indicate the location where the population is assigned. The census tract/block numbering area and census block for the crews of vessels is infinitesimally small, requiring only one "line" with the same from and to points and a couple of shape points so that the polygon appears as a triangle. The coordinates on record type 1 and record type 2 will place the census block on the shore inside the land block with the same 3-digit collection block number, not in the water as shown on the census maps. The area measurement enclosed for the special crews of vessels census tract/BNA and block is defined as zero. On the map sheet, there is an anchor symbol in the water, accompanied by the census tract/BNA number and the Z-suffixed block number. The location of that anchor symbol is arbitrary and reflects neither the location of the vessel(s) at the time of the census nor the crews-of-vessels census tract/BNA and block as it appears in the TIGER/Line file. Figure 1 Crews of Vessels in the TIGER File Representation of Leading Zeros in Census Tract/BNA Numbers The field containing the census tract number will have leading zeros. The Census Bureau uses this presentation to be consistent with the data files and other digital representation of the census tract/BNA numbers; the leading zeros are not part of the census tract number and do not appear in Census Bureau printed reports or on the map sheets that display these areas. Record Number and Version Number In the TIGER/Line files, there is a 4-character version number and a permanent 10-character record number that is unique across all files. We are reserving all version numbers 0 through 5000 for use by the Bureau of the Census. The 10-digit record number will not exceed the value 231-1, and will represent the same line segment in later versions of this file. Users can use the record number to have a unique identifier for every line segment in the TIGER data base. Users should store the record number and the version number associated with each line segment in local systems to ensure their ability to match with later versions of the file. When adding features to the file, local users should flag all such records as a local addition, and assign a version number greater than 5000 so as not to duplicate a Census Bureau-assigned record number that may appear elsewhere in the national file. Coordinates Coordinates are expressed in standard FIPS notation, where a negative latitude represents the Southern Hemisphere and a negative longitude represents the Western Hemisphere. All coordinates are expressed as a signed integer with six decimal places of precision implied. (In the illustration below, the figure shows the decimal point; the file does not contain the decimal point.) Actual TIGER/Line File Latitude 15 Deg. S to 72 Deg. -15.000000 to +72.000000 Longitude 64 Deg. W to 131 Deg. E -64.000000 to -180.000000 +131.000000 to +179.999999 Corporate Corridors and Offset Corporate Boundaries A corporate corridor is a narrow, linear part of an incorporated place. The corporate corridor may include an addressable street or road but is too narrow to include the structures, such as houses, apartments, or businesses, that front along the street or road. The corporate corridor includes the street or a portion of the street and/or the right-of-way or a portion of the right-of-way within the incorporated place but excludes the structures addressed to the street from the incorporated place. Where the incorporated place lies on only one side of the street center line, this is called an offset corporate boundary, whereas a corporate corridor lies on both sides of the street center line. In order to reduce the overprinting of symbols on the census maps, a corporate corridor is shown with only one symbol along the center line rather than a symbol that follows the outer boundary of a place. For TIGER/Line files, record type 1 will not have any information to indicate that the street or right-of-way lies within a corporate corridor or offset boundary and that the address ranges lie outside the corporate corridor or offset boundary. However, the street name and address ranges will be duplicated on lines with census feature class codes of F11, nonvisible offset boundary, and F12, nonvisible corporate corridor. When data users find duplicate address ranges where one of the duplicates is on a line with a census feature class code of F11 or F12, do not use the address range for the indicated side of the street for geocoding. Likewise, do not use the street name and address ranges on the nonvisible boundary features for mapping or vehicle routing. The duplicate street name will be found on record type 5 and the duplicate address ranges will be found on record type 6. 1990 CENSUS TIGER/LINE FILES AND 1980 GBF/DIME-FILES The 1990 Census TIGER/Line files provide 1980 census block numbers only for areas covered by the 1980 GBF/DIME-Files. Some 1980 census block numbers in the GBF/DIME-Files may not agree with the 1980 data products (summary tape files and maps). Subsequently, during the processing to convert the GBF/DIME-Files to the TIGER data base format, additional 1980 census block numbers were deleted or changed. The number of 1980 block numbers deleted or changed will vary by individual GBF/DIME-File. ZIP Codes appear only for street features with address ranges; address ranges appear only for the major builtup areas of the United States, typically confined to the urban cores of most 1980 census urbanized areas. Unlike the 1980 GBF/DIME-Files, the 1990 Census TIGER/Line files do not require that the address ranges appear as a low-to-high sequence starting at the "from" end of a street segment. Because the 1990 Census TIGER/Line file format differs from the 1980 GBF/DIME-File format, software designed to use the GBF/DIME-File format will require some changes to use the 1990 Census TIGER/Line files directly. Selected Field Definitions: VERSION: The version number appears in all record types except 5. For the 1990 Census TIGER/Line file, the version has the value "3". LAND: The Landmark Feature Identification Number is not a permanent number; the Census Bureau assigns a new Landmark Feature Identification Number each time a new version of the TIGER/Line file is produced. The Landmark Feature Identification Number is not stored in the Census Bureau's TIGER data base, but is assigned during the extraction of the data. There may be gaps in the sequence of the Landmark Feature Identification Number in Record Type 7 because of the way this information is extracted. LANAME: This field contains the landmark feature name; there may be some abbreviations to ensure that the name will fit in the 30-character field. SOURCE: The Source Codes are the same as those that appear on Record Type 1. TLID: The Record Number is the linkage between the polygon identification number and the line segments in Record Type 1. The Record Number is the same number that appears in position 6 to 15 of Record Type 1. CENID: The Census Bureau maintains the TIGER data base in a series of partitions; the CENID is an internal Census Bureau identifier used to number the polygons uniquely. POLYID: The polygon identification number is a temporary number assigned to every polygon in the TIGER data base. Although this number is part of the TIGER data base design, it is a dynamic number and can change between versions of the TIGER/Line files. The TIGER data base does not contain permanent polygon identifiers as it does for line segments. POLYID is unique only within CENID; it may not be unique within any particular county-based TIGER/Line file. RTPOINT: The Census Bureau is including an additional field that we are calling RTPOINT to allow for possible future expansion of polygon information. This field has the value "P" in the 1990 Census TIGER/Line files. MAXID: For each CENID, the Census Bureau has established a maximum value for the RECNUM. We do not anticipate that any file will have this RECNUM. MINID: For each CENID, the Census Bureau established the beginning, or lowest, value for the RECNUM. This value may or may not exist in the TIGER data base, or in any TIGER/Line file. HIGHID: For each CENID, the HIGHID is the highest value that the Census Bureau has used in the MINID ... MAXID range of values. The HIGHID may or may not appear in the TIGER/Line file, especially if only a few records in the TIGER/Line file are stored in that particular CENID. Address Range Updates During the course of our precensus and postcensus activities, we updated some address ranges and ZIP Codes within the geographic areas that contain this information. In addition, we have extended the geographic area that contains address range information in the following 1980 GBF/DIME-File areas. For each GBF/DIME-File area, we list the counties that have extended address coverage beyond that appearing in the 1980 GBF/DIME-File. Atlanta, GA Cobb, Clayton, Douglas, Fulton, Gwinnett, Henry, and Rockdale Counties, GA Baltimore, MD Carroll and Harford Counties, MD Boston, MA Bristol, Essex, Middlesex, Norfolk, Plymouth, and Worcester Counties, MA Chicago, IL DuPage, Kane, Kendall, Lake, McHenry, and Will Counties, IL Cincinnati, OH Clermont and Warren Counties, OH and Boone, Campbell, and Kenton Counties, KY Dallas-Fort Worth, TX Collin, Denton, Johnson, Parker, Rockwall, and Tarrant Counties, TX Fall River, MA Bristol County, MA and Newport County, RI Gary-Hammond, IN Lake and Porter Counties, IN Houston, TX Brazoria, Fort Bend, and Harris Counties, TX Lakeland-Winter Haven, FL Polk County, FL Long Branch-Asbury Park, NJ Monmouth and Ocean Counties, NJ Los Angeles, CA Los Angeles County, CA Minneapolis-St. Paul, MN Anoka, Carver, Dakota, Hennepin, Scott, and Washington Counties, MN Nassau-Suffolk, NY Suffolk County, NY New York, NY Westchester County, NY and Bergen County, NJ Paterson, NJ Passaic County, NJ Philadelphia, PA Bucks, Chester, Delaware, and Montgomery Counties, PA and Burlington, Camden, and Gloucester Counties, NJ Pittsburgh, PA Allegheny, Beaver, and Westmoreland Counties, PA Providence, RI Bristol, Kent, Providence, and Washington Counties, RI and Bristol, Norfolk, and Worcester Counties, MA Riverside-San Bernardino, CA Riverside County, CA Distribution Unit The Census Bureau makes the 1990 Census TIGER/Line files available to the public by county and statistically equivalent entity, in accordance with the county boundaries that are in the TIGER/Line file based on the 1990 Boundary and Annexation Survey. Thus, there are separate TIGER/Line files for the independent cities of Virginia and the other entities that the Census Bureau recognizes as statistically equivalent to counties.