Identification_Information
Abstract
Purpose
Supplemental Information
Data_Quality_Information
Spatial_Data_Organization_Information
Entity_and_Attribute_Information
Detailed Description
Overview
Distribution_Information
Metadata_Reference_Section
Identification_Information
Citation_Information
Originator: K.J.Hitt
Publication_Date: 1994
Title: Refining 1970's Land-Use Data with 1990 Population Data.
Series_Information
Series_Name: OFR
Description
Abstract
The National Water-Quality Assessment (NAWQA) Program's Potomac River Basin
study unit is an integrated water-quality assessment designed to address a
broad array of water-quality properties in several environmental media at
various spatial and temporal scales. These properties are then related to
natural and human factors that can influence the quality of water. During
a 3-year period of intensive data collection and analysis, hundreds of
water-quality characters were measured in five environmental media within
surface-water and ground-water systems. Sampled surface-water media include
streamwater, streambed sediment, aquatic biological communities, and aquatic
biological tissues. This investigation was conducted as part of a nation-
wide study to help assess the nation,s water-quality conditions.
The NAWQA program has developed a procedure to define urban (residential)
land use by overlaying Bureau of the Census 1990 population density at the
block group level on USGS 1970s digital land-use data from 1:250,000-
and 1:100,000-scale maps (Hitt, 1994) . First, the population density of
the census block groups is calculated, and then the block group boundaries
are overlaid on the 1970s land-use information. Any area having a population
of 1,000 or more people per square mile (386 people per square kilometer) is
re-classified as new "residential" land use in the derivative map.
This data set reflects the urban change within the Potomac River Basin
study area, as well as boundaries for their Fixed Site Network.
Key_words:
Land use
Population density
Land development
Urbanization
Purpose
The NAWQA Program intends to use this coverage to represent current
residential land use because up-to-date, nationally consistent land use
data--which are needed to compare and contrast NAWQA study units--are
not available.
Supplemental_Information
Procedures_Used
Revisions
Reviews_Applied
Related_Spatial_and_Tabular_Data_Sets
Other_References_Cited
Notes
Time_Period_of_Content
Currentness_Reference
Status
Progress: Coverage not formally reviewed.
Maintenance_and_Update_Frequency
Spatial_Domain
Bounding_Coordinates
West_Bounding_Coordinate: -79.74150601
East_Bounding_Coordinate: -76.17953713
North_Bounding_Coordinate: 40.22694018
South_Bounding_Coordinate: 37.85990675
Keywords
Theme
Theme_Keyword_Thesaurus: None
Theme_Keyword: Overlay of GIRAS land use with population density at block group level
Place
Place_Keyword_Thesaurus: None
Place_Keyword: Potomac River Basin NAWQA study unit started in FY 1991
Stratum
Stratum_Keyword_Thesaurus: None
Stratum_Keyword:
Temporal
Temporal_Keyword_Thesaurus: None
Temporal_Keyword:
Access_Constraints
Use_Constraints
The data represent only the residential component of "urban and built-up"
land and do not account for commercial, industrial, or transportation uses.
Population density is not a direct measure of structures on the land.
Assigning population density and classifying new land use by entire block
groups tends to over-represent the aerial extent of new "residential" areas.
We did not remove block groups coded as "water" in the TIGER/Line files.
(Hitt, 1994)
Point_of_Contact: See Distribution_Information for contact information.
Data_Set_CreditDerosier, Brakebill, Denis, & Kelley
Security_Information
Security_Classification_System: None
Security_Classification: UNCLASSIFIED
Security_Handling_Description: None
Native_Data_Set_Environment: dgux UNIX, ARC/INFO version 7.0.4
Cross_Reference
Originator: K.J. Hitt
Publication_Date: 1994
Publication_Time:
Title: Refining 1970s Land-Use Data with 1990 Population Data
Edition:
Geospatial_Data_Presentation_Form: bPoint Attribute Tab
Series_Information
Series_Name: le
Issue_Identification:
Publication_Information
Publication_Place:
Publisher:
Other_Citation_Details:
Online_Linkage: ' -'
Larger_Work_Citation:
Data_Quality_Information
Attribute_Accuracy
Attribute_Accuracy_Report: See Entity_Attribute_Information
Quantitative_Attribute_Accuracy_Assessment
Attribute_Accuracy_Value: See Explanation
Attribute_Accuracy_Explanation:
Attribute accuracy is described, where present, with each
attribute defined in the Entity and Attribute Section.
Logical_Consistency_Report: Polygon topology present.
Completeness_Report
Positional_Accuracy
Horizontal_Positional_Accuracy
Horizontal_Positional_Accuracy_Report:
Vertical_Positional_Accuracy
Vertical_Positional_Accuracy_Report:
Lineage: See Supplemental_Information for overview.
Process_Steps
Process_Step
Available in download Arc/Info export file
Spatial_Data_Organization_Information
Direct_Spatial_Reference_Method: Vector
Point_and_Vector_Object_Information
SDTS_Terms_Description
SDTS_Point_and_Vector_Object_Type: Point
Point_and_Vector_Object_Count: 18291
SDTS_Point_and_Vector_Object_Type: String
Point_and_Vector_Object_Count: 42943
SDTS_Point_and_Vector_Object_Type: GT-polygon composed of chains'
Point_and_Vector_Object_Count: 18292
Spatial_Reference_Information
Horizontal_Coordinate_System_Definition
Planar
Map_Projection:
Map_Projection_Name: ALBERS
Longitude_of_Central_Meridian: -78
Latitude_of_Projection_Origin: 23
Latitude_of_First_Standard_Parallel: 29.5
Latitude_of_Second_Standard_Parallel: 45.5
False_Easting: 0.00000
False_Northing: 0.00000
Geodetic Model
Horizontal_Datum_Name:
Ellipsoid_Name: Clarke 1866
Semi-major_Axis: 6,378,206.4
Denominator_of_Flattening: 294.98
Entity_and_Attribute_Information
Detailed_Description
Entity_Type
Entity_Type_Label: GIRAS.PAT
Entity_Type_Definition: Polygon Attribute Table
Entity_Type_Definition_Source: ARC/INFO
Attribute:
Attribute_Label: -
Attribute_Definition: Polygon Attribute Table
Attribute_Definition_Source: ARC/INFO
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: -
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Attribute:
Attribute_Label: AREA
Attribute_Definition: Area of poly/region in square coverage units
Attribute_Definition_Source: Computed
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: Positive real numbers
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Attribute:
Attribute_Label: PERIMETER
Attribute_Definition: Perimeter of poly/region in coverage units
Attribute_Definition_Source: Computed
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: Positive real numbers
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Attribute:
Attribute_Label: GIRAS#
Attribute_Definition: Internal feature number
Attribute_Definition_Source: Computed
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: Sequential unique positive integer
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Attribute:
Attribute_Label: GIRAS-ID
Attribute_Definition: User-assigned feature number
Attribute_Definition_Source: User-defined
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: Integer
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Attribute:
Attribute_Label: STAID
Attribute_Definition: Station Identification Number
Attribute_Definition_Source: USGS
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: Character
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Attribute:
Attribute_Label: STAT_MIN
Attribute_Definition: Minimum Station Identification Number
Attribute_Definition_Source: USGS
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: Integer
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Attribute:
Attribute_Label: LUCODE
Attribute_Definition: Land Use code, Anderson Level II
Attribute_Definition_Source: USGS GIRAS DATA
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: Integer 1 - 30
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Attribute:
Attribute_Label: NEWLU
Attribute_Definition: Updated land use code
Attribute_Definition_Source: USGS
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: 0 - no updated, 10 - updated to residential
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Attribute:
Attribute_Label: OLDLU
Attribute_Definition: Old land use code prior to update
Attribute_Definition_Source: USGS
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: Integer, 1 - 30
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Attribute:
Attribute_Label: STATION_ID
Attribute_Definition: Station Identification w/o leading zero
Attribute_Definition_Source: USGS
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: integer
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Attribute:
Attribute_Label: CODE
Attribute_Definition: ANderson Level I land use code
Attribute_Definition_Source: USGS
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: -6
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Entity_Type
Entity_Type_Label: GIRAS.LUT
Entity_Type_Definition: look up table
Entity_Type_Definition_Source: USGS
Attribute:
Attribute_Label: -
Attribute_Definition: look up table
Attribute_Definition_Source: USGS
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: -
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Attribute:
Attribute_Label: LUCODE
Attribute_Definition: Anderson Level II land use code
Attribute_Definition_Source: USGS
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: integer 1 - 30
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Attribute:
Attribute_Label: NAME1
Attribute_Definition: Anderson Level I land use name
Attribute_Definition_Source: USGS
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: Character
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Attribute:
Attribute_Label: NAME2
Attribute_Definition: Anderson Level II land use name
Attribute_Definition_Source: USGS
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: Character
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Attribute:
Attribute_Label: SYMBOL1
Attribute_Definition: Shade symbol for Level I landuse, colornames.shd
Attribute_Definition_Source: USGS
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: Integer
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Attribute:
Attribute_Label: CODE
Attribute_Definition: ANderson Level I code
Attribute_Definition_Source: USGS
Attribute_Domain_Values
Enumerated_Domain
Enumerated_Domain_Value: Integer 1 - 7
Enumerated_Domain_Value_Definition
Enumerated_Domain_Value_Definition_Source:
Overview_Description
Entity_and_Attribute_Overview
The following is a "generic" list of attributes in the block
group/land use (BGLU) coverage. The exact list will vary from
coverage to coverage because the input coverages might have been
processed slightly differently for the different study units within
the NAWQA Program. The land use coverages of some of the larger study units
such as Georgia/Florida (GAFL) had to be subdivided into smaller areas for
processing. The names of these coverages and the derivative BGLU coverages
have a suffix appended the coverage name; for example, GAFL was divided into
three parts indicated by N (northern part of study unit), M (middle part),
and S (southern part).
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC
1 AREA 8 18 F 5
9 PERIMETER 8 18 F 5
17 GAFLBGLUN# 4 5 B -
21 GAFLBGLUN-ID 4 5 B -
25 GAFLN# 4 5 B - from GIRAS coverage
29 GAFLN-ID 4 5 B - from GIRAS coverage
33 LUCODE 2 2 I - from GIRAS coverage
35 STATECTY 5 5 I -
40 ST 2 2 C -
42 CNTYNAME 23 23 C -
65 GAFLBG# 4 5 B - from block group coverage
69 GAFLBG-ID 4 5 B - from block group coverage
73 BGIX 7 7 I - from block group coverage
80 BGI 12 12 I - from block group coverage
92 NEWLU 2 2 I - derived from pop density
** REDEFINED ITEMS **
35 FIPS:ST 2 2 I -
37 FIPS:CO 3 3 I -
35 FIPS 5 5 I -
33 LUC1 1 1 I -
The attributes of interest are LUCODE, BGI, and NEWLU.
LUCODE is the original USGS land use data uses Anderson Level II land use
category in the Geographic Information Retrieval Analysis System (GIRAS)
digital land use quad as described in Anderson and
others (1976). The source coverage is the GIRAS land use coverage processed
by the NAWQA study unit or national synthesis (U.S. Geological Survey, 1990).
NEWLU is the updated land use code that is assigned based on 1990
population density. Valid codes are 0 and 10. A code of 0 means that
the polygon has the same land use as in the original data base and was
not changed during the procedure to refine residential land use. A 10
means that "new residential" land use was assigned to the polygon if
the polygon was not called "urban and built-up" in the original data
base.
4. Procedures used to create or automate data
The following data sources were used to derive this coverage:
a) 1970s land use and land cover digital data from 1:250,000- and
1:100,000-scale maps (GIRAS data)
b) 1990 Census of population at the block group level
c) 1990 TIGER/Line files at the block group level
* * *
a) 1970s land use and land cover digital data from 1:250,000- and
1:100,000-scale maps (GIRAS data)
The land use data (U.S. Geological Survey, 1990) was processed
by the NAWQA study unit or NAWQA national synthesis from GIRAS
format to ARC/INFO format and was clipped to the study unit
boundary. The land use coverage was overlaid with the
1:100,000-scale county coverage to obtain state and county codes.
Some of the land use coverages also were overlaid with NAWQA basin
boundaries, so they have extra items such as STAID and basin
names, which were not used in this analysis. Some coverages
have other items, such as ACRES and MI2, that are not used in this
analysis either. Below is a generalized items list for a land
use coverage:
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC
1 AREA 4 12 F 3
5 PERIMETER 4 12 F 3
9 GAFLN# 4 5 B -
13 GAFLN-ID 4 5 B -
17 LUCODE 2 2 I -
19 STATECTY 5 5 I -
24 ST 2 2 C -
26 CNTYNAME 23 23 C -
** REDEFINED ITEMS **
19 FIPS:ST 2 2 I -
21 FIPS:CO 3 3 I -
19 FIPS 5 5 I -
b) 1990 Census of population at the block group level
Approximately 7 million blocks, which are the basic geographic units
in the Census, are defined for the United States and outlying
areas. To make managing the data easier, population and housing unit
digital data were summarized on the block group level
(summary level "740" in the data extraction programs supplied by
the Bureau of the Census, 1991a). A block group is a cluster of
blocks having the same first digit of the 3-digit identifying
numbers within a census tract/block numbering area. The location
of the block group is represented in the Census data base by an
internal point whose geographic coordinates place it approximately
at the center of the block group. The point data for each block
group includes statistical attributes such as area (square
kilometers) and population and housing unit counts. The boundaries
of the block group are not included; the only geographic reference
is the internal point. To perform spatial analysis on the Census
data, the data must be linked by the block group geographic key to
the 1990 TIGER/Line Census files, which are described in section 4c
(Bureau of the Census, 1991b).
The block group population points were processed for the
conterminous United States into ARC/INFO format (point
coverage, USPOP90, available in DSDL). To create population
coverages for each study unit, the national coverage was
clipped to a 2,000 meter buffer around the study unit boundary.
Each point is referenced by a 12-digit block group identifier
that is composed of state, county, and block group number.
The block group number is composed of a 6-digit census
tract/block numbering area code and a 1-digit block group code.
The 12-digit identifier is used to relate the points in a study
unit population coverage to the polygons in a study unit
TIGER/Line file.
Below is an example of the 12-digit block group identifier:
Block group identifier: 131171301001 Component:
xx State FIPS code
xxx County FIPS code
xxxxxx Census tract/Block no. area
x Block group
Here is an example of the items in the point attribute
table of one of the study unit population coverages:
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC
1 AREA 4 12 F 3
5 PERIMETER 4 12 F 3
9 GAFLCEN902# 4 5 B -
13 GAFLCEN902-ID 4 5 B -
17 GAFLCEN90# 4 5 B -
21 GAFLCEN90-ID 4 5 B -
25 ST 2 2 C -
27 CENSUS_ID 19 19 C -
46 AREA_WATER 4 11 F 3
50 AREA_LAND 4 11 F 3
54 POP90 4 9 B -
58 HU90 4 9 B -
62 PDENS 4 11 F 3
66 HDENS 4 11 F 3
70 CLASS 4 5 B -
74 ABBV 4 4 C -
78 BGI 12 12 I -
90 BGC 12 12 C -
102 ST2 2 2 C -
104 CO2 3 3 C -
107 CTBNA2 6 6 C -
113 BG2 1 1 C -
** REDEFINED ITEMS **
27 BG 1 1 C -
34 COUNTY 3 3 C -
37 COUSUBCE 3 3 C -
40 CENPLACE 4 4 C -
44 STATE 2 2 C -
28 CTBNA 6 6 C -
102 BGRED 12 12 C -
c) 1990 TIGER/Line files at the block group level
The 1990 Census TIGER/Line files provide digital geographic
data for all 1990 Census map features and boundaries. The
files are organized by county, and although block group
boundaries are not specifically coded, they can be assembled
from block boundaries. The TIGER/Line files contain no
statistical information; the files provide geographic layers
for spatial analysis. The layers are linked to data in the
Census of population and housing by the block group geographic
key (Bureau of the Census, 1991c,d).
NAWQA is processing the TIGER/Line county files into ARC/INFO
and is assembling them into polygon coverages of block groups
by state. If a study unit falls into only one state, the block
group boundaries for that state are clipped to the study unit
boundary. If a study unit falls into more than one state, all
of the state polygon coverages are clipped to the study unit
boundary separately and then are joined together. Each polygon
is referenced by a 12-digit block group identifier that is
composed of state, county, and block group number. The
12-digit identifier is used to relate the polygons in a study
unit TIGER/Line coverage to the points in a study unit
population file.
Here is an example of the items in the polygon attribute
table of one of the study unit block group coverages:
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC
1 AREA 8 18 F 5
9 PERIMETER 8 18 F 5
17 GAFLBG# 4 5 B -
21 GAFLBG-ID 4 5 B -
25 BGIX 7 7 I -
32 STATECTY 5 5 I -
37 BGI 12 12 I -
** REDEFINED ITEMS **
32 FIPS:ST 2 2 I -
34 FIPS:CO 3 3 I -
32 FIPS 5 5 I -
The first step in calculating population density at the block group
level is to summarize population and land area for each block group in
the study unit population coverage. (Block groups may be represented
by more than one population point in that data base.) The total
population for each block group is calculated by summarizing the
population for every point having the same unique 12-digit block group
identifier. The total land area of the block group is calculated by
summarizing the land area of every point having the same unique block
group identifier. The ARC/INFO "FREQUENCY" command accomplishes this
(see the ARC/INFO aml below). The frequency items (fields used to
identify unique combinations of codes) are state (STATE), county
(COUNTY), census tract/block numbering area (CTBNA), and block group
(BG). (Because of a limit in the FREQUENCY command, the 12-digit block group
identifier as one field could not be used.) The summary items
(fields that are summarized for each unique occurrence of the
frequency items) are 1990 population (POP90) and land area
(AREA_LAND). The result is a lookup table listing each unique
12-digit block group identifier, the total population for each block
group identifier, and the total land area for each block group
identifier. Fields for population density (PDENS) and density class
(CLASS) are added.
The next step is to calculate population density (PDENS) for each
block group, which equals the total population for the block group
divided by the total land area of the block group. (Block groups
having zero land area are excluded.) Each block group is assigned to
one of 5 classes of population density. The assigned density class
(CLASS) is stored in the lookup table by block group identifier.
Density of people per square kilometer Assigned density class
--------------------------------------------- ---------------------------------
Greater or equal to 0 and less than 50 1-"rural development"
Greater or equal to 50 and less than 386 2-"low density residential"
Greater or equal to 386 and less than 2,000 3-"medium density residential"
Greater or equal to 2,000 and less than 5,000 4-"high density residential"
Greater or equal to 5,000 5-"very high density residential"
Using these five density classes, the 1970s land use from the GIRAS
data base can be updated to reflect 1990 residential conditions. We
will label any polygon having a population density of 386 or more
people per square kilometer as "urban" (residential) and will
calculate NEWLU code equals 10 in the output coverage. Thus, areas
that were not called "urban" in the original GIRAS coverage may be
called "urban" in the derivative map.
The aml that summarizes the population, calculates the density,
and assigns the density classes to the block groups is listed below:
/* aml to summarize population density by block group and assign
/* population density classes 1-5
&args covname
&if [null %covname%] &then &s covname = [response Study unit]
&if [exists %covname%POP.FREQ -info] &then ~
&s kdel [delete %covname%POP.FREQ -info]
FREQUENCY %COVNAME%CEN902.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
The resulting lookup table, GALFPOP.FREQ, is defined as:
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC
1 FREQUENCY 4 5 B -
5 BGI 12 12 I -
17 BGC 12 12 C -
29 STATE 2 2 C -
31 COUNTY 3 3 C -
34 CTBNA 6 6 C -
40 BG 1 1 C -
41 POP90 8 18 F -
49 AREA_LAND 8 18 F 3
57 PDENS 4 11 F 3
61 CLASS 1 1 I -
** REDEFINED ITEMS **
29 BGRED 12 12 C -
Overlay 1990 population density on the existing
land use map for each NAWQA study area
The polygons in the block group coverage and the land use coverage are
overlaid using ARC/INFOs polygon-on-polygon overlay capabilities, for
example:
IDENTITY GAFLBG /GIRAS/GAFLN GAFLBGLUN POLY 60 JOIN
^^^^^^ ^^^^^^^^^^^^ ^^^^^^^^^
block land use output
group coverage coverage
coverage
Overlaying the polygons of the land use coverage on the polygons of
the block group coverage creates the new BGLU coverage that is a
combination of land use and block group polygons. The land use and
block group attributes are joined in the output coverage so that now
each polygon can be identified by a Level II land use category as well
as by a 12-digit block group identifier. The item called NEWLU is
added to the output coverage.
Categorize the derivative land use map according to the
population density using the definition of "residential" land use
The lookup table of population density calculated from 1990 Census data is
linked to the derivative land use map by the 12-digit block group
identifier. Each polygon in the derivative map is assigned the population
density for the corresponding block group regardless of what was the
original land use in the polygon.
When reclassifying the land use polygons, it was assumed that any area
called "urban or built-up" during the 1970s still will be "urban or
built-up" land (Level I code 1) today since urban land is not likely to
revert back to other uses. We also assume that any area that was called
"water" (Level I code 5) still is "water." The urban and water areas are
excluded when the land use is re-classified by population density.
Any polygon meeting the following criteria is assigned a new land use of
"residential": 1) the original land use of the polygon is not urban, 2) the
original land use of the polygon is not water, and 3) the population
density of the polygon is greater or equal to 386 people per square
kilometer (1,000 people per square mile)--density categories 3, 4, or 5 as
listed above.
The INFO code to categorize the polygons in the derivative land use map is:
SEL GAFLBGLUN.PAT
REL GAFLPOP.FREQ BY BGI ORD
RESEL LUC1 NE 1 AND LUC1 NE 5 AND $1CLASS GE 3
CALC NEWLU = 10
Potomac NAWQA fixed site boundaries (Fixed_bnd) were added to the data set
using IDENTITY (ARC/INFO). Any attributes within the .PAT listed
in the above section that are not present in the coverage GIRAS were dropped.
FINAL ATTRIBUTE LIST OF GIRAS
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC NAME
1 AREA 8 18 F 5 -
9 PERIMETER 8 18 F 5 -
17 GIRAS# 4 5 B - -
21 GIRAS-ID 4 5 B - -
25 STAID 8 8 C - Station Identification
33 STAT_MIN 7 7 I - Minimum Station number
40 LUCODE 2 2 I - land use code (GIRAS)
42 NEWLU 2 2 I - New land use code
44 OLDLU 2 2 I - Old land use code prior to
** REDEFINED ITEMS **
26 STATION_ID 7 7 I - STAID w/o leading Zero
40 CODE 1 1 I - Anderson Level I code
5. Revisions made to data (revision number, date, description)
None.
6. Reviews applied to data (review type, date, person, description)
Colleague, District Chief Approval
Local scientists in the NAWQA study unit have verified that the
results give a reasonable indication of urbanization that has occurred
in the study unit since the 1970s land-use data were compiled.
The data you have secured from the USGS have not received Directors
approval and as such are provisional and subject to revision. The data
are released on the condition that neither the USGS nor the United
States Government may be held liable for any damages resulting from
its authorized or unauthorized use.
7. Related spatial and tabular data sets and programs
USPOP90 -- 1990 census of population
point coverage for the conterminous United States
available in Distributed Spatial Data Library (DSDL)
GIRAS.lut -- Lookup table containing names of land uses and symbol numbers.
8. References cited
Anderson, J.R, Hardy, E.E., Roach, J.T., and Witmer, R.E., 1976, A
land use and land cover classification system for use with remote
sensor data: U.S. Geological Survey Professional Paper 964, 28 p.
Blomquist,J.D., Fisher,G.T., Denis,J.M., Brakebill,J.W., and Werkheiser,W.H., 1996,
Water-Quality Assessment of the Potomac River Basin: Basin Description and Analysis
of Available Nutrient Data, 1970-90. U.S. Geological Survey Water-Resources
Investigations Report 95-4221, 88 pp.
Bureau of the Census, 1991a, Census of population and housing, 1990:
Public Law 94-171 data (United States) [machine-readable data
files on CD-ROM]: Washington, D.C., The Bureau [producer and
distributor].
Bureau of the Census, 1991b, Census of population and housing, 1990:
Public Law 94-171 data technical documentation
[machine-readable files on CD-ROM]: Washington, D.C., The Bureau.
Bureau of the Census, 1991c, TIGER/Line Census Files, 1990
[machine-readable data files on CD-ROM]: Washington, D.C., The
Bureau [producer and distributor].
Bureau of the Census, 1991d, TIGER/Line Census Files, 1990 technical
documentation: Washington, D.C., The Bureau, 63 p.
Gerhart, J.M., and Brakebill, J.W., Design and Implementation of a Sampling
Strategy for a Water-Quality Assessment of the Potomac River Basin. U.S.
Geological Surveys Water-Resources Investigations Report 96-4034, 31pp.
Hitt, K.J.,1994. Refining 1970s Land-Use Data with 1990 Population Data to
indicate New Residential Development. U.S. Geological Survey Water-Resource
Investigations Report 94-4250, 15p.
U.S. Geological Survey, 1990, Land use and land cover digital data
from 1:250,000- and 1:100,000-scale maps, Data user guide 4: Reston,
Va., U.S. Geological Survey, 25 p.
Notes
The use of trade, product, or firm names is for descriptive purposes only and does not
imply endorsement by the U.S. Government.
Entity_and_Attribute_Detail_Citation: Not Available
Distribution_Information
Arc/Info Export format:
Use Load to local disc:
GIRAS Landuse.e00
Gunzipped SDTS Topological Vector Profile (TVP) format:
Use Load to local disc:
GIRAS Landuse.tgz
PC Zipped SDTS Topological Vector Profile (TVP) format:
GIRAS Landuse.zip
STDS files were created from ARC/INFO ARCSDTS
If the end user of an ARCSDTS file does not have access to the
SDTSARC command, the file can be converted into an Arc coverage
by first uncompressing it with the UNIX gzip command, which will
create a UNIX tar file. If the compressed ARCSDTS file does not have
a .tgz or .gz suffix, it must be renamed (UNIX mv command) to have
one. Second, the user must perform a UNIX tar xvof command on
the tar file and all SDTSEXPORT .DDF files will be loaded into the
workspace the "tar xvof" command is issued. Last, the user must
issue the Arc SDTSIMPORT command with the < in_transfer_prefix >
being the first four characters of the prefix to the .DDF files and the
< out_cover > being the prefix to the tar file. PC users can use unzip
to create STDS .DDF files from downloaded .zip files.
Contact
John W Brakebill
Geographer
U.S. Geological Survey
8987 Yellow Brick Road
Baltimore, Maryland 21237
Phone: 410-238-4200
Fax: 410-238-4210
email: jwbrakeb@usgs.gov
Metadata_Reference_Section
Metadata_Date: 19980128
Metadata_Contact: jwbrakeb
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: 19940608
Metadata_Time_Convention: Local Time
Metadata_Security_Information:
Metadata_Security_Classification_System: None
Metadata_Security_Classification: UNCLASSIFIED
Metadata_Security_Handling_Description: None
Last modified: 98-02-04.15:05:46.Wed