UCSB Biogeography Lab
Table of Contents
Identification Information
Data Quality Information
Spatial Data Organization Information
Spatial Reference Information
Entity and Attribute Information
Distribution Information
Metadata Reference Information
Contact Information
Layer Contents
Description: Boundaries of the 7.5 minute quadrangles of California to be used for geographic reference.
Supplemental Information: n/a
Data Set Status: in use
West Bounding Coordinate: -124.5048
East Bounding Coordinate: -114.2648
North Bounding Coordinate: 41.9886
South Bounding Coordinate: 32.4234
Theme Keyword: Geographic grid
Browse Graphic File Name: usgs24k.gif
Browse Graphic File Description: 7.5' quadrangle boundaries of California
.
Browse Graphic File Type: GIF
Use Restrictions: none
Access Limitations: none
Native Data Set Environment:
ARC/INFO software version 7.0.3 running on IBM RS6000 with AIX 3.2.5
Raster File Format: n/a
Raster File Sensor: n/a
Vector File Format: ARCE7 (ARC/INFO Export format, version 7)
Nonspatial File Format: n/a
II. DATA QUALITY INFORMATION
Attribute Accuracy:
Quad names were assigned from the Geographic Names Information System (GNIS) database and therefore should contain the correct official names. However, since the list did not include the coordinates of this quad, the assignment was made based on placenames of points within quads. Some discrepancies were detected, especially when placenames occurred on adjoining quads. This caused a few quads to be unlabeled and a few to have its neighbor's label. These were corrected as they were detected, but it is possible some duplicate names may still occur.
Attribute Accuracy Explanation: n/a
Logical Consistency Report: n/a
Completeness Report:
Quadrangles cover the entire state of California and all polygons have a name corresponding to the USGS quadrangle map series name. All quadrangle polygons have a full set of analytical attributes calculated by CA-GAP.
Horizontal Positional Accuracy: n/a
Horizontal Positional Accuracy Explanation:
This coverage was created from a grid in latitude and longitude coordinates. At that stage it was perfectly accurate. Positional errors would only arise in the projection from geographic coordinates into Albers equal area. The DENSIFY 0.03125 option was given in the PROJECT file to provide reasonable curvature of grid lines with spacing of vertices at 0.03125 degrees, or 1/4 of the side of a 7.5 minute quad.
Vertical Positional Accuracy: n/a
Vertical Positional Accuracy Explanation: n/a
Source Information:
The attribute data for this layer were primarily derived by the California Gap Analysis Project from the GAP database and from ancillary sources as described here. Many of the attributes were derived directly from CA-GAP land-cover or land ownership/management layers or from the predicted vertebrate distributions. Data on sensitive species and communities and areas containing concentrations of those biodiversity elements were obtained from the California Department of Fish and Game's Natural Heritage Division. Road and population data were derived from the 1990 Census. See the Process Description section below for details on the sources and how they were used.
Source Date: circa 1990-1998.
Source Distance Resolution: 50 meters
Process Description:
A grid of 7.5 minutes of latitude and longitude was created with the GENERATE command that included all of California. The Geographic Names Information System (GNIS) database was sorted for unique occurrences of each USGS quad number and a point coverage was generated with one point per quad. The quad number was one of the attributes of this point coverage. The 7.5 minute grid was superimposed on the point coverage with the IDENTITY command, adding the grid ID number to the attributes. Thus, there was a link between the grid ID number and the USGS number in the point coverage. The list of quad numbers and names was made into another INFO table so that the quad names could also be related to the grid ID. The grid attributes were edited to provide quad numbers and names for grid cells without them. The grid coverage was RESELECTed to retain only the cells within the state (i.e., that had quad numbers and names). The coverage was then projected into the standard Albers projection with the DENSIFY 0.03125 option in the PROJECT file to provide reasonable curvature of grid lines with spacing of vertices at 0.03125 degrees, or 1/4 of the side of a 7.5 minute quad.
The attributes were processed as described here.
PCTPVT: This is the percentage of the quadrangle that is privately owned. This was calculated by intersecting the usgs24k and ma (land ownership and management) layers and running the ARC FREQUENCY command on the resulting .PAT file for USGS24K-ID and OWNER, summarized by AREA. This was converted to a percentage by dividing the area of private ownership by the LAND_HA item.
LAND_HA: This is the area of the quadrangle, excluding surface water mapped for the land ownership layer.
PPIDENS: This is the density of boundary between public and private ownerships. The land ownership/management layer was reclassified into these two categories, and all arcs were deleted except those that separated them. The IDENTITY command was run to determine the quadrangle that each line segment occurred in, and FREQUENCY was run to summarize the length by quadrangle. Density was calculated by dividing length by quadrangle area to normalize for the slight difference in quadrangle size as a function of latitude and for partial quadrangles that fall partly in the ocean or neighboring states.
SNAPCT: This is the percentage of the quadrangle contained within Significant Natural Areas (SNAs) identified by the California Department of Fish and Game's Natural Heritage Division. The Significant Natural Areas Program analyses data from the Department's Natural Diversity Data Base, which contains over 22,000 locational records of over 1,200 sensitive natural communities and species. SNAs are identified as:
The January, 1998, version of the SNA coverage was obtained from Fish and Game. This was intersected with the usgs24k layer and summarized with the FREQUENCY command to calculate percentage.
ROAD: Road data from the 1990 1:100,000 scale TIGER files (Bureau of the Census, 1989) were buffered with a buffer width related to the class of road (see table below). This buffer operation was used to estimate the area of land actually impacted by the presence of each road, where freeways were assumed to affect a greater spatial extent than dirt roads. A "roadedness" index was calculated for each quadrangle by summing the area of buffered roads with the FREQUENCY command, dividing that sum by the total area in the quadrangle, and multiplying by 100.
Table 1. Buffer widths assigned to road classes for calculating roadedness index.
|
Census Feature Class Code |
Description |
Buffer width (m) |
|
A10-A18 |
Primary road with limited access or interstate highway |
500 |
|
A20-A28 |
Primary road without limited access (US and state highway) |
250 |
|
A30-A38 |
Secondary and connecting road (state and county roads) |
100 |
|
A40-A48 |
Local, neighborhood, or rural road |
100 |
|
A50-A53 |
Vehicular trail (4 wheel drive route) |
25 |
|
A70-A73 |
Other-Biking or walking trail |
0 |
PCTCONV: The CA-GAP land-cover layer was used to identify urban and agricultural land use types. These human-dominated land uses were intersected with the usgs24k coverage and summarized with the FREQUENCY command.
MEANDIST: Status 1 and 2 managed areas were extracted from the CA-GAP land management layer (ma) and converted to a raster in ARC/GRID with 100 m cells. The EUCDISTANCE command was run to calculate the distance from every cell in the state to the nearest status 1 or 2 area. Cells in status 1 or 2 managed areas were given a distance of zero. The usgs24k coverage was also converted to a raster. The distances within each quadrangle to the nearest status 1 or 2 area were summarized with ZONALSTATS, using the usgs24k raster as the zone grid with the MEAN operator. Mean distances were converted to kilometers for this attribute.
NDDBRICH: The California Department of Fish and Game's Natural Heritage Division (NHD) maintains the Natural Diversity Data Base (NDDB), which contains over 22,000 locational records of over 1,200 sensitive natural communities and species (i.e., biodiversity elements). Fish and Game generalized the coordinate locations for us to the quadrangle of occurrence. These lists of communities and species were tallied as counts of the number of unique elements in each quadrangle.
G1G2RICH: This attribute was also derived from the NDDB summaries described for the NDDBRICH attribute. In this case, however, only elements with a global ranking of G1 or G2 were counted. These elements are considered the most rare and vulnerable by the national network of heritage programs.
POPDENS: Population data from the 1990 census were obtained from the Consortium for International Earth Science Information Network (CIESIN). CIESIN had interpolated block group data to a 1 km lattice of the United States. We converted this lattice into a grid. By summing population from all the one kilometer cells in a quadrangle (ZONALSTATS) and dividing by quadrangle area, an estimate of population density was derived.
VULNCOM: Highest priority plant communities were identified in CA-GAP based in part on management status and partly on other factors such as their rarity and endemism, their condition, and additional information about the kinds of activities that are likely to occur in each type. Within the set of plant communities, we distinguished seven categories. The first two categories include all those rated as rare by the NHD (S1 or S2). Of these, the highest priority (Group A) is for rare communities with less than 20% level of status 1 and 2 management, while the second priority types have more than 20% (Group B). For widespread community types, priorities were set based on a combination of two factors: percentage of status 1 and 2 lands and an index of threat. The threat index was calculated as a sum of roadedness and projected population growth, normalized by their mean values, and rescaled so that absence of threat is equal to zero. The first group (Group C) of common communities was characterized by a threat index > 3.75, indicating a relatively high degree of either past disturbance or future loss. Note that this threshold level was selected as a natural break in the set of plant communities, not on any a priori or theoretical basis. It had the further advantage of allowing us to divide communities into approximately equal-sized groups. Virtually all Group C community types were also relatively under-represented (< 20% status 1 and 2). The remaining four groups all appear relatively less threatened by roads or future development (threat index < 3.75) and were categorized based on their level of protection into roughly equal numbers of types in each group. We used the same break points as shown in Table 5-2, i.e., 10%, 20%, and 50%, in decreasing order of priority. Five exceptions were made to these general rules. Four types that were rated as rare by NHD were mapped over extensive areas by CA-GAP, perhaps due to differences in interpretation. We therefore chose to assign Mojave Mixed Steppe, Upland Redwood Forest, Westside Ponderosa Pine Forest, and Eastside Ponderosa Pine Forest to groups G, E, E, and D respectively, as if they were not rare types. Also, we assigned Tamarisk Scrub to group G because it is not a native community type and in fact is generally considered a pest species. The remaining urban, agricultural, and non-vegetated land cover types were assigned to group H that has no conservation priority for its vegetation values. There may still be important habitats and other ecosystem values, however, in the non-vegetated types (e.g., water bodies, sand dunes, rock outcrops, etc.).
The area of each grouping was summed for each quadrangle and then weighted (see table below) to calculate a site score. The area of lands already designated as management classes 1 or 2 were excluded from the site scoring because their contribution was already considered in the vulnerability ratings of plant communities. Sites with large proportions of highly vulnerable communities outside of existing managed areas score highest while those with well-represented communities or human land uses would score close to zero.
Table 2. Weighting for plant communities by priority group.
|
Priority Group |
% Status 1 and 2 |
Threat Index |
Weight |
|
A |
< 20 |
� |
1.0 |
|
B |
>20 |
� |
0.75 |
|
C |
� |
high |
0.75 |
|
D |
<10 |
low |
0.5 |
|
E |
10-20 |
low |
0.3 |
|
F |
20-50 |
low |
0.1 |
|
G |
>50 |
low |
0.0 |
|
H (non-vegetated) |
� |
� |
0.0 |
STAT12: The area of status 1 and 2 managed areas was summarized by quadrangle and converted to a percentage by dividing the area by the LAND-HA attribute and multiplying by 100.
BRICH: A list of species was predicted for each land-cover polygon (see metadata for predicted vertebrate distributions for methods), the predicted distributions were summed into species richness maps for the four major taxonomic groups: breeding land birds, mammals, amphibians, and reptiles. This involved resampling the species distributions mapped on habitat polygons to a uniform grid system of equal-area units. Every species present in any polygon within the quadrangle with a suitability category of 4 or 5 was counted. BRICH is the number of breeding land birds per quadrangle.
MRICH: Similar to BRICH for mammals.
ARICH: Similar to BRICH for amphibians.
RRICH: Similar to BRICH for reptiles.
Native Data Structure: spatial vector
Raster File Row (Line) Count: n/a
Raster File Column (Sample) Count: n/a
Raster File Vertical (Band) Count: n/a
Raster File Number of Bytes per Pixel: n/a
Geographic Coordinate Units: Degrees, minutes and decimal seconds
Map Projection Name: Albers Conical Equal Area
Map Projection Description:
Projection ALBERS
Units METERS
Spheroid CLARKE1866
Parameters:
Distance Resolution (meters): 50
Altitude Resolution (meters): n/a
V. ENTITY/ATTRIBUTE INFORMATION
Attribute Label:
|
Attribute |
Attribute Description |
|
USGS# |
GNIS quad number |
|
QUADNAME |
GNIS 7.5 minute quad name |
|
PCTPVT |
% of quadrangle in private ownership |
|
LAND_HA |
Hectares of land |
|
PPIDENS |
Density of public-private land boundaries in quadrangle |
|
SNAPCT |
% of quadrangle in Significant Natural Areas |
|
ROAD |
% of quadrangle in roaded area |
|
PCTCONV |
% of quadrangle converted to human uses |
|
MEANDIST |
Mean distance of quadrangle to nearest status 1 or 2 areas |
|
NDDBRICH |
# of different biodiversity elements in Natural Diversity Data Base in quadrangle |
|
G1G2RICH |
# of different biodiversity elements ranked G1 or G2 in Natural Diversity Data Base in quadrangle |
|
POPDENS |
Density of people per sq. km. from 1990 Census |
|
VULNCOM |
Weighted score of proportion of quadrangle with each plant community type, where the weight is based on the vulnerability of that type |
|
STAT12 |
% of quadrangle in Status 1 or 2 managed areas |
|
BRICH |
# of breeding land birds in quadrangle |
|
MRICH |
# of mammals in quadrangle |
|
ARICH |
# of amphibians in quadrangle |
|
RRICH |
# of reptiles in quadrangle |
Attribute Definition Source:
Geographic Names Information System (GNIS) database
Entity and Attribute Detail Citation: n/a
Distributor:
phone: 805-893-3438
fax: 805-893-3146
e-mail: fd@geog.ucsb.edu
ftp address:
ftp://ftp.biogeog.ucsb.edu/pub/org/biogeog/data/gap_analysis
URL:
http://www.biogeog.ucsb.edu/projects/gap/gap_data.html
Distribution Liability:
The University of California assumes no responsibility for application of the data beyond their original intent.
Standard Order Process:
Data are available through anonymous ftp and the World Wide Web at the ftp address and URL address listed under Distributor.
File Decompression Technique:
ARC/INFO export file (ARCE7) with NONE compression option.
Transfer Size: 1.1 Mb in gzip compressed format; 4.2 Mb uncompressed format
Metadata Date: 07/09/98
Metadata Standard Name: Metadata Standards for Gap Analysis
Metadata Standard Version: 09/05/94
Metadata Review Date: n/a
Metadata Contact:
Contact Person Primary: Dr. David Stoms
Contact Mail Address:
Contact Voice Telephone: (805) 893-7655
Contact Facsimile Telephone: (805) 893-3146
Contact Electronic Mail Address:
stoms@geog.ucsb.edu
INFO Table Schema and Range of Legal Values
USGS24K.PAT-Polygon attribute table
|
Start column |
Attribute |
Attri-bute Para-meters |
Attribute Description |
|||
|
17 |
USGS# |
4 |
5 |
B |
- |
GNIS quad number |
|
21 |
QUADNAME |
40 |
40 |
C |
- |
GNIS 7.5 minute quad name |
|
61 |
PCTPVT |
4 |
6 |
F |
1 |
% of quadrangle in private ownership, legal values from 0.0 to 100.0 |
|
65 |
LAND_HA |
4 |
10 |
F |
3 |
Hectares of land |
|
69 |
PPIDENS |
4 |
8 |
F |
3 |
Density of public-private land boundaries in quadrangle, legal values from 0.00 to 4.029 |
|
73 |
SNAPCT |
4 |
6 |
F |
1 |
% of quadrangle in Significant Natural Areas, legal values from 0.0 to 100.0 |
|
77 |
ROAD |
4 |
6 |
F |
1 |
% of quadrangle in roaded area, legal values from 0.0 to 100.0 |
|
81 |
PCTCONV |
4 |
6 |
F |
1 |
% of quadrangle converted to human uses, legal values from 0.0 to 100.0 |
|
85 |
MEANDIST |
4 |
10 |
F |
3 |
Mean distance of quadrangle to nearest status 1 or 2 areas, legal values from 0 to 46.344 km |
|
89 |
NDDBRICH |
3 |
3 |
I |
- |
# of different biodiversity elements in Natural Diversity Data Base in quadrangle, legal values from 0 to 56 |
|
92 |
G1G2RICH |
3 |
3 |
I |
- |
# of different biodiversity elements ranked G1 or G2 in Natural Diversity Data Base in quadrangle, legal values from 0 to 24 |
|
95 |
POPDENS |
4 |
10 |
F |
3 |
Density of people per sq. km. from 1990 Census, legal values from 0.000 to 6,339.845 |
|
99 |
VULNCOM |
4 |
8 |
F |
4 |
Weighted score of proportion of quadrangle with each plant community type, where the weight is based on the vulnerability of that type, legal values from 0.0000 to 97.9110 |
|
103 |
STAT12 |
4 |
6 |
F |
1 |
% of quadrangle in Status 1 or 2 managed areas, legal values from 0.0 to 100.0 |
|
107 |
BRICH |
3 |
3 |
I |
- |
# of breeding land birds in quadrangle, legal values from 1 to 126 |
|
110 |
MRICH |
3 |
3 |
I |
- |
# of mammals in quadrangle, legal values from 3 to 66 |
|
113 |
ARICH |
3 |
3 |
I |
- |
# of amphibians in quadrangle, legal values from 0 to 15 |
|
116 |
RRICH |
3 |
3 |
I |
- |
# of reptiles in quadrangle, legal values from 0 to 52 |