(THIS IS AN EXAMPLE OF DOCUMENTATION FOR 1994 NAWQA STUDY UNIT
BLOCK GROUP BOUNDARY COVERAGE)
METADATA FOR PUGTBG
(Substitute any 4-letter NAWQA study unit abbreviation for PUGT.)
/* Identification Information */
Data_Set_Identity: PUGTBG -- 1990 Census block groups for FY 1994 NAWQA study units
Identification_Code: N/A
Theme_Keyword: 1990 Census block groups
Thematic_Accuracy: See Attribute Descriptions
Thematic_Accuracy_Explanation: See Attribute Descriptions
Logical_Consistency: Polygon topology present
Completeness: See Data_Set_Description
Data_Set_Citation:
Hitt, K.J., 1994, Digital map file of 1990 Census block group boundaries
for 1994 NAWQA study units processed from Bureau of the Census 1990
TIGER/Line files: Washington, D.C., The Bureau (producer and distributor),
1:100K scale, ARC/INFO format.
Native_Data_Set_Environment: UNIX
Use_Restrictions: See Data_Set_Description
Access_Restrictions: Not reviewed
Security_Classification: UNCLASSIFIED
/* Spatial Reference */
Native_Data_Set_Structure: ARC/INFO COVER
Horizontal_Coordinate_System: Planar
Map_Projection_Name: ALBERS
Map_Projection_Coordinate Units: METERS
Horizontal_Datum_Name: NAD27
Ellipsoid_Name: CLARKE1866
Vertical_Datum_Name: NGVD29
Longitude_of_Central_Meridian: -96 0 0.000
Latitude_of_Projection_Origin: 23 0 0.000
Latitude_of_First_Standard_Parallel: 29 30 0.000
Latitude_of_Second_Standard_Parallel: 45 30 0.000
False_Easting: 0.00000
False_Northing: 0.00000
X-Shift: 0.0000000000
Y-Shift: 0.0000000000
Point/Vector_Object_Information:
Number of points: 3193
Number of lines: 8902
Number of line segments: 108165
Number of polygons: 3194
Point_Object_Information:
Number of control points: 156
Horizontal_Positional_Accuracy: N/A
Horizontal_Positional_Accuracy_Explanation: N/A
Vertical_Positional_Accuracy: N/A
Vertical_Positional_Accuracy_Explanation: N/A
West_Bounding_Coordinate: -123.0851
East_Bounding_Coordinate: -120.9385
North_Bounding_Coordinate: 49.4054
South_Bounding_Coordinate: 46.3913
Data_Set_G-Polygon_Outer_G-Ring: N/A
Data_Set_G-Polygon_Exclusion_G-Ring: N/A
Geographic_Keyword_Name: NAWQA study units started in FY 1994
Geographic_Keyword_Type: Location
/* Status Information */
Data_Set_Status:
Not reviewed
Release_Date: N/A
Maintenance_and_Update_Frequency: N/A
/* Metadata Reference Section */
Metadata_Date: 941021.171959
Metadata_Review_Date: N/A
Metadata_Future_Review_Date: N/A
Metadata_Contact: kjhitt
/* Source Information */
Source_Identity:
Hitt, K.J., 1994, Digital map file of 1990 Census block group boundaries
for 1994 NAWQA study units processed from Bureau of the Census 1990
TIGER/Line files: Washington, D.C., The Bureau (producer and distributor),
1:100K scale, ARC/INFO format.
/* Processing History Information */
/* Per Process Step */
Process_Description: DISSOLVE PUGTBG PUGTBG2 STCNTRBG
Process_Date: 09/27/1994 (MDY)
Process_Time: 14:44
Process_Description: RENAME PUGTBG2 PUGTBG
Process_Date: 09/27/1994 (MDY)
Process_Time: 14:46
Process_Description: COPY PUGTBG /SRV3/NAWQA/KJH/SUBG/PUGTBG
Process_Date: 10/18/1994 (MDY)
Process_Time: 12:23
Process_Description: DOCUMENT PUGTBG COPY /HOME/TRIM/SU91BG/ALBEBG KJHITT
Process_Date: 10/21/1994 (MDY)
Process_Time: 16:19
/* Distribution Information */
Distribution_Contact: Kerie Hitt, USGS-WRD-NAWQA
Distribution_Liability: N/A
Transfer_Options: N/A
Transfer_Instructions: N/A
Fees: N/A
Turnaround: N/A
/* Contact Information */
Contact_Organization: USGS-WRD-NAWQA
Contact_Person: Kerie Hitt
Contact_Position: N/A
Contact_Mailing Address: N/A
Contact_Physical Location: N/A
Contact_Voice_Telephone: N/A
Contact_Facsimile_Telephone: N/A
Contact_Electronic_Mail_Address: N/A
Contact_Instructions: email kjhitt@usgs.gov or phone 703/648-6854
/* Entity/Attribute Information */
Data_Base_Identity: PUGTBG
Partition_Identity: N/A
Entity_Type_label: PUGTBG.PAT
---------------------------------
Entity_Type_Definition: BLOCK GROUP POLYGONS FOR FY94 NAWQA STUDY UNITS PAT FILE
Entity_Type_Definition_Source: 1990 TIGER/LINE FILES
Number_of_Attributes_in_Entity: 13
Attribute_Label: -
Attribute_Definition: BLOCK GROUP POLYGONS FOR FY94 NAWQA STUDY UNITS PAT FILE
Attribute_Definition_Source: 1990 TIGER/LINE FILES
EA_Domain_Values: -
EA_Units_of_Measure: N/A
EA_Measurement_Precision: N/A
EA_Beginning_Date: N/A
EA_Ending_Date: N/A
EA_Accuracy: N/A
EA_Accuracy_Explanation: N/A
EA_Measurement_Frequency: N/A
Attribute_Label: AREA
Attribute_Definition: Area of poly in square coverage units
Attribute_Definition_Source: Computed
EA_Domain_Values: Positive real numbers
EA_Units_of_Measure: N/A
EA_Measurement_Precision: N/A
EA_Beginning_Date: N/A
EA_Ending_Date: N/A
EA_Accuracy: N/A
EA_Accuracy_Explanation: N/A
EA_Measurement_Frequency: N/A
Attribute_Label: PERIMETER
Attribute_Definition: Perimeter of polygon in coverage units
Attribute_Definition_Source: Computed
EA_Domain_Values: Positive real numbers
EA_Units_of_Measure: N/A
EA_Measurement_Precision: N/A
EA_Beginning_Date: N/A
EA_Ending_Date: N/A
EA_Accuracy: N/A
EA_Accuracy_Explanation: N/A
EA_Measurement_Frequency: N/A
Attribute_Label: PUGTBG#
Attribute_Definition: Internal feature number
Attribute_Definition_Source: Computed
EA_Domain_Values: Sequential unique positive integer
EA_Units_of_Measure: N/A
EA_Measurement_Precision: N/A
EA_Beginning_Date: N/A
EA_Ending_Date: N/A
EA_Accuracy: N/A
EA_Accuracy_Explanation: N/A
EA_Measurement_Frequency: N/A
Attribute_Label: PUGTBG-ID
Attribute_Definition: User-assigned feature number
Attribute_Definition_Source: User-defined
EA_Domain_Values: Integer
EA_Units_of_Measure: N/A
EA_Measurement_Precision: N/A
EA_Beginning_Date: N/A
EA_Ending_Date: N/A
EA_Accuracy: N/A
EA_Accuracy_Explanation: N/A
EA_Measurement_Frequency: N/A
Attribute_Label: BGI
Attribute_Definition: BLOCK GROUP IDENTIFIER
Attribute_Definition_Source: 1990 TIGER/LINE FILES
EA_Domain_Values: VALID BLOCK GROUPS
EA_Units_of_Measure: N/A
EA_Measurement_Precision: N/A
EA_Beginning_Date: N/A
EA_Ending_Date: N/A
EA_Accuracy: N/A
EA_Accuracy_Explanation: N/A
EA_Measurement_Frequency: N/A
Attribute_Label: STATE
Attribute_Definition: STATE 2-DIGIT FIPS CODE
Attribute_Definition_Source: TIGER/LINE FILES
EA_Domain_Values: 01-56
EA_Units_of_Measure: N/A
EA_Measurement_Precision: N/A
EA_Beginning_Date: N/A
EA_Ending_Date: N/A
EA_Accuracy: N/A
EA_Accuracy_Explanation: N/A
EA_Measurement_Frequency: N/A
Attribute_Label: COUNTY
Attribute_Definition: COUNTY 3-DIGIT FIPS CODE
Attribute_Definition_Source: TIGER/LINE FILES
EA_Domain_Values: 001-999
EA_Units_of_Measure: N/A
EA_Measurement_Precision: N/A
EA_Beginning_Date: N/A
EA_Ending_Date: N/A
EA_Accuracy: N/A
EA_Accuracy_Explanation: N/A
EA_Measurement_Frequency: N/A
Attribute_Label: CTBNA
Attribute_Definition: CENSUS TRACT/BLOCK NUMBERING AREA
Attribute_Definition_Source: TIGER/LINE FILES
EA_Domain_Values:
EA_Units_of_Measure: N/A
EA_Measurement_Precision: N/A
EA_Beginning_Date: N/A
EA_Ending_Date: N/A
EA_Accuracy: N/A
EA_Accuracy_Explanation: N/A
EA_Measurement_Frequency: N/A
Attribute_Label: BG
Attribute_Definition: BLOCK
Attribute_Definition_Source: TIGER/LINE FILES
EA_Domain_Values:
EA_Units_of_Measure: N/A
EA_Measurement_Precision: N/A
EA_Beginning_Date: N/A
EA_Ending_Date: N/A
EA_Accuracy: N/A
EA_Accuracy_Explanation: N/A
EA_Measurement_Frequency: N/A
Attribute_Label: TOTPOP90
Attribute_Definition: TOTAL 1990 POPULATION FOR BLOCK GROUP
Attribute_Definition_Source: USPOP90 COVERAGE IN DSDL (PREPARED FROM 1990 CENSUS DATA)
EA_Domain_Values:
EA_Units_of_Measure: N/A
EA_Measurement_Precision: N/A
EA_Beginning_Date: N/A
EA_Ending_Date: N/A
EA_Accuracy: N/A
EA_Accuracy_Explanation: N/A
EA_Measurement_Frequency: N/A
Attribute_Label: PDENS
Attribute_Definition: POPULATION DENSITY PER SQUARE KILOMETER
Attribute_Definition_Source: DERIVED FROM USPOP90 BY 1990 POPULATION DIVIDED BY AREA_LAND (KM2)
EA_Domain_Values:
EA_Units_of_Measure: N/A
EA_Measurement_Precision: N/A
EA_Beginning_Date: N/A
EA_Ending_Date: N/A
EA_Accuracy: N/A
EA_Accuracy_Explanation: N/A
EA_Measurement_Frequency: N/A
Attribute_Label: CLASS
Attribute_Definition: POPULATION DENSITY CATEGORY ASSIGNED BY NAWQA FOR LAND USE ANALYSIS
Attribute_Definition_Source: ASSIGNED BY NAWQA FROM POPULATION DENSITY CATEGORIES
EA_Domain_Values: 1,2,3,4,5
EA_Units_of_Measure: N/A
EA_Measurement_Precision: N/A
EA_Beginning_Date: N/A
EA_Ending_Date: N/A
EA_Accuracy: N/A
EA_Accuracy_Explanation: N/A
EA_Measurement_Frequency: N/A
Data_Set_Description:
1. Abstract
This is a polygon coverage of the 1990 Census TIGER/Line block groups
clipped to the FY 1994 NAWQA study unit boundaries. Approximately 230,000
block groups exist in the United States.
Descriptors:
United States
Population
Census
2. Applications that use this data
This coverage could be used for any GIS application requiring the
Census block group as the basic geographic unit. The block groups
are the geographic areas used to extract the population points from
the P.L. 94-171 data base for the coverage USPOP90 that is in the
Distributed Spatial Data Library.
2.1 Intended use of data
The NAWQA nutrients national synthesis intends to use population
density by block group to derive urban land use for water-quality
studies.
2.2 Limitations of data
The TIGER files have no shorelines. Coastal areas have their
boundaries extended approximately 3 miles into the ocean. Areas
bounding the Great Lakes and other large inland waterbodies have their
boundaries extended proportionally into the waterbody.
The coverage contains no arc attributes, only polygon attributes.
3. Attribute discussion
The NAWQA block group coverage .pat files contain the following
attributes, where XXXX is the 4-letter NAWQA study unit abbreviation:
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC
1 AREA 8 18 F 5
9 PERIMETER 8 18 F 5
17 XXXXBG# 4 5 B -
21 XXXXBG-ID 4 5 B -
25 BGI 12 12 I -
37 TOTPOP90 4 9 B -
41 PDENS 4 11 F 3 PEOPLE/KM2
45 CLASS 4 5 B -
** REDEFINED ITEMS **
25 STATE 2 2 I -
27 COUNTY 3 3 I -
30 CTBNA 6 6 I -
36 BG 1 1 I -
BGI--------block group identifier, consisting of:
BGI 0 1
columns 123456789012
xx - state FIPS
xxx - county FIPS
xxxxxx - Census tract/block numbering area (CTBNA)
x - Block group within CTBNA
xxxxxxxxxxxx - Unique block group identifier
Census block groups are the next to smallest geographic area in the
Bureau of the Census hierarchy of geographic presentation, which
is:
United States
Region
Division
State
County
County subdivision
Census tract/Block numbering area (BNA)
Block group
Block
Census blocks are small areas bounded on all sides by visible
features such as streets, roads, streams, and railroad tracks, and by
invisible boundaries such as city, town, township, and county limits,
property lines, and short, imaginary extensions of streets and roads.
Tabulation blocks, used in census data products, are in most cases
the same as collection blocks, used in the census enumeration. In
some cases, collection blocks have been "split" into two or more
parts required for data tabulations. Tabulation blocks do not
cross the boundaries of counties, county subdivisions, places,
census tracts or block numbering areas, American Indian and Alaska
Native areas, congressional districts, voting districts, urban or
rural areas, or urbanized areas. The 1990 census is the first for
which the entire United States and its possessions are
block-numbered.
Blocks are numbered uniquely within each census tract or BNA. A
block is identified by a three-digit number, sometimes with a
single alphabetical suffix. Block numbers with suffixes generally
represent collection blocks that were "split" in order to identify
separate geographic entities that divide the original block. For
example, when a city limit runs through data collection block 101,
the data for the portion inside the city is tabulated in block
101A and the portion outside, in block 101B. A block number with
the suffix "Z" represents a "crews-of-vessels" entity for which
the Census Bureau tabulates data, but that does not represent a
true geographic area; such a block is shown on census maps
associated with an anchor symbol and a census tract or block
numbering area with a .99 suffix.
A block group is a cluster of blocks having the same first digit
of the 3-digit identifying numbers in a census tract/BNA. In
population data tabulations, a geographic block group may be
split. Therefore, when linked with the point population and
housing coverage (USPOP90), SOME OF THE BLOCK GROUPS CONTAIN MORE
THAN ONE POPULATION POINT. Block groups do not cross census tract
or block numbering area boundaries.
Census tracts are small, relatively permanent statistical
subdivisions of a county. They are identified by a four-digit
basic number and may have a two-digit suffix. Census tract numbers
range from 0001 to 9499.9 and are unique within a county. The
suffix .99 identifies a census tract that was populated entirely by
persons aboard one or more ships.
Block numbering areas (BNAs) are small statistical subdivisions of
a county for areas where census tracts are not established. They
are identified by a four-digit basic number and may have a
two-digit suffix. BNA numbers range from 9501 to 9980.99 and are
unique within a county. The suffix .99 identifies a census tract
that was populated entirely by persons aboard one or more ships.
Suffixes in the range of .80 through .98 usually identify census
tracts or BNAs that were revised or created during the 1990 census.
Some of these revisions may have resulted in census tracts or BNAs
that have extremely small land area and may have little or no
population or housing.
Census tracts and BNAs do not cross county boundaries.
TOTPOP90---total 1990 population for the block group. The total population
is summed from unique block group numbers occurring in the coverage USPOP90,
which resides in the Distributed Spatial Data Library (DSDL).
PDENS------population density per square kilometer. Density is calculated
from population divided by AREA_LAND in the USPOP90 coverage for points
having AREA_LAND greater than zero.
CLASS------population density category assigned by NAWQA for land use
analysis. The valid codes are 1-5, and classes 3,4, and 5 are considered
to be "urban" land:
(metric units)
1 = pop density ge 0 and lt 50 people per km2
2 = pop density ge 50 and lt 386 people per km2
3 = pop density ge 386 and lt 2000 people per km2
4 = pop density ge 2000 and lt 5000 people per km2
5 = pop density ge 5000 people per km2
(U.S. units)
1 = pop density ge 0 and lt 130 people per mi2
2 = pop density ge 130 and lt 1000 people per mi2
3 = pop density ge 1000 and lt 5180 people per mi2
4 = pop density ge 5180 and lt 13000 people per mi2
5 = pop density ge 13000 people per mi2
STATE------State 2-digit FIPS code
COUNTY-----County 3-digit FIPS code
CTBNA------Census tract/Block numbering area
BG---------Block group
4. Procedures used to create or automate data
The NAWQA study unit boundaries are from the coverage ALL58, which
is maintained by Naomi Nakagaki and Kerie Hitt. This coverage
contains the NAWQA study unit boundaries obtained from the study
units mostly at 1:2,000,000 scale.
The block group boundaries are from the 1990 Census Bureau TIGER/
Line files. The TIGER/Line files were converted into ARC/INFO and
processed into block groups by Steve Denowski (WRD, Madison,
Wisconsin) and the Environmental Protection Agency's National
Geographic Information System Program using ARC/INFO aml programs
developed jointly between USGS and EPA.
Steve Denowski converted the raw TIGER files into ARC/INFO
coverages and then derived the block groups from the resulting
ARC/INFO coverages for about half of the states. EPA supplied
county block group coverages for the rest of the states. The
county coverages were joined to form state coverages.
The general processing steps used by WRD for creating the block
group coverages for all of the counties in a state are shown
below. (Details about the amls can be obtained from Steve
Denowski, phone 608/238-9333, extension 160.) The ssccc means the
FIPS code for a particular county, where ss represents the state
component and ccc represents the county component:
1. Project the geographic coordinates of the TIGER line file into
albers equal area and build the coverage.
2. Create a join file with the RECNUM and CFCC items in
it. (These items are taken from the tl_ssccc.acode file for the
coverage.)
3. Sort the join file on the RECNUM.
4. Merge the join file with the tl_ssccc.aat using the RECNUM as
joinitem.
5. Dissolve the tl_ssccc coverage by the TRACTBLK item with the
POLY option (not the NET option)
6. Add the item 'CENSUS' to the dissolved coverage called
tl_ssccctb.
7. Move TRACTBLK to CENSUS in the tl_ssccctb coverage.
8. Redefine the first 7 characters of CENSUS as BG.
9. Add a new item called 'BGI' and calculate BGI = BG.
10. Dissolve the tl_ssccctb coverage by BGI using the POLY option.
11. Add a new item called 'FIPS' to the resulting coverage
tl_sscccbg and calculate FIPS = ssccc.
Once the block group coverages exist for all of the counties in
the state, the county coverages are joined into one coverage for
the entire state. When the counties are joined together, the
7-digit block group number no longer is unique because the
numbering system starts over in each county. So the county and
state codes are needed to distinguish the block groups from county
to county and from state to state. The 12-digit block group number is
derived from the 7-digit BGI as follows:
1. Change the item named BGI to BGIX. BGIX is the original
7-digit block group number that is unique only within a county.
2. Add the new item 'BGI' to the coverage .pat
3. Calculate BGI = BGIX
Calculate BGI = BGI + (FIPS:CO * 10000000 )
Calculate BGI = BGI + (FIPS:ST * 100000000000 )
4. Remove BGIX and other items.
The block group coverages for the state are clipped using the
NAWQA study unit boundary if the study unit falls in only one
state. If the NAWQA study unit occupies more than one state, each
of the state block group polygon coverages is clipped to the study
unit boundary separately, and then all of the pieces are joined
into one block group coverage for the whole study unit. For
example, the following commands produce the block group coverage
for the Nevada Basin and Range NAWQA (NVBR), which lies in
California (CA) and Nevada (NV).
CLIP CABG NVBR NVBRBG1 POLY .0000001 (clip Calif portion from Calif BGs)
CLIP NVBG NVBR NVBRBG2 POLY .0000001 (clip Nevada portion from Nevada BGs)
MAPJOIN NVBRBG POLY ALL (put the Calif and Nevada portions together)
1st cov: NVBRBG1
2nd cov: NVBRBG2
3rd cov: NONE
Total population, population density, and class are computed from the
point population coverage USPOP90 using the following aml that creates
an INFO lookup table sorted on BGI. The items for total population,
population density, and class subsequently are added to the coverage
.pat file and calculated equal to the corresponding fields in the
lookup table.
&args covname
&if [null %covname%] &then &s covname = [response 'Study unit']
&s covname = [translate %covname%]
&if [exists %covname%POP.FREQ -info] &then ~
&s kdel [delete %covname%POP.FREQ -info]
FREQUENCY %COVNAME%POP90.PAT %COVNAME%POP.FREQ
STATE
COUNTY
CTBNA
BG
END
POP90
AREA_LAND
END
DROPITEM %COVNAME%POP.FREQ %COVNAME%POP.FREQ CASE#
ADDITEM %COVNAME%POP.FREQ %COVNAME%POP.FREQ BGI 12 12 I 0 FREQUENCY
ADDITEM %COVNAME%POP.FREQ %COVNAME%POP.FREQ BGC 12 12 C # BGI
ADDITEM %COVNAME%POP.FREQ %COVNAME%POP.FREQ PDENS 4 11 F 3
ADDITEM %COVNAME%POP.FREQ %COVNAME%POP.FREQ CLASS 1 1 I
&data arc info
ARC
SEL %COVNAME%POP.FREQ
REDEFINE
29
BGRED
12
12
C
MOVE BGRED TO BGC
CALC BGI = BGC
RESEL AREA_LAND NE 0
CALC PDENS = POP90 / AREA_LAND
ASEL
RESEL PDENS GE 0 AND PDENS LT 50
CALC CLASS = 1
ASEL
RESEL PDENS GE 50 AND PDENS LT 386
CALC CLASS = 2
ASEL
RESEL PDENS GE 386 AND PDENS LT 2000
CALC CLASS = 3
ASEL
RESEL PDENS GE 2000 AND PDENS LT 5000
CALC CLASS = 4
ASEL
RESEL PDENS GE 5000
CALC CLASS = 5
ASEL
Q STOP
&end
***********
5. Revisions made to data (revision number, date, description)
None.
6. Reviews applied to data (review type, date, person, description)
The coverage has not been reviewed formally.
7. Related spatial and tabular data sets and programs
The 1990 population data by block group is located in the
Distributed Spatial Data Library in the layer called USPOP90.
(The block group number can be derived from the fields in the
CENSUS_ID. The items STATE, COUNTY, CTBNA, and BG must be
recombined in that order into a 12-digit code for block group that
matches the 12-digit BGI in the block group coverage.)
The NAWQA study unit boundaries are in the coverage called ALL58.
This can be obtained from Naomi Nakagaki (WRD, Sacramento, phone
916/978-4637) or Kerie Hitt (phone 703/648-6854).
8. References cited
Bureau of the Census, 1991a, TIGER/Line Census Files, 1990 (machine-
readable data files): Washington, D.C., The Bureau (producer and
distributor).
Bureau of the Census, 1991b, TIGER/Line Census Files, 1990 technical
documentation: Washington, D.C., The Bureau, 63 p.
Hitt, K.J., 1992, Digital map file of 1990 population and housing
data for the conterminous United States processed from Bureau of
the Census, 1991, Census of population and housing, 1990: Public
Law 94-171 data (United States) (machine-readable data files):
Washington, D.C., The Bureau (producer and distributor), 1:2M
scale, ARC/INFO format.
9. Notes