This data set is a subset of a master data set called QUADTILE that contains boundaries for all 7.5' quadrangles from 36 to 43 degrees north latitude and 87 to 92 west longitude. Arcs from QUADTILE can also be used to produce statewide base maps for 15' (1:62,500 scale), 30' x 60' (1:100,000), and 1 degree x 2 degree (1:500,000) quadrangles.
Any hardcopies utilizing DNR data sets shall clearly indicate their source. If the licensee has modified the data in any way they are obligated to describe the types of modifications they have performed on the hardcopy map. Licensee specifically agrees not to misrepresent DNR data sets, nor to imply that changes they made were approved by DNR.
These data are not to be used for commercial profit.
GIS Processing: ISGS Staff Documentation: D. Nelson and S. Beaverson Quality Control: ISGS Staff, D. Nelson
Data set was DESCRIBED and coverage files listed to determine the feature types present. In this data set, the following feature types were found and checked: polygons, arcs, labels, nodes, and annotation. The presence of spatial indices was also checked.
For PAT and AAT files, each ITEM was checked for the following:
- DOMAIN of allowable values - adherence of values to the DOMAIN - definition of ITEMS - requirement of all UNIQUE values for an item - logic of ITEMS REDEFINED over other ITEMS - length of ITEM name as regards conversion to shape fileBUILD statuses of data sets were checked, as were LABELERRORS and NODEERRORS (where appropriate), and PROJECTION definition.
The presence of a BND file was verified.
The presence and location of TICS were checked.
Polygon and chain-node topology present. There are no dangling arcs. There is one polygon label per polygon, except for universe polygon. Boundary values appropriate for map projection and map units. "Fuzzy" tolerance is suitable for nominal scale. Some minor attribute errors were found and corrected. Two polygons had MAPNAME = CLINTON. The one on the state boundary was renamed CLINTON IA-IL. There are no attribute values outside the appropriate domains.
Differences between this edition (1.1) and the previous edition (1.0) are: Tics and arcs have been regenerated. Tics have been added at every quadrangle corner. Vertices have been added to every arc at 1.5' intervals to reduce shape changes due to projection of the data. Arcs and polygon topology have been added for the Danby quad in southwestern Illinois, increasing the number of quadrangles to 1072. Two attribute values have been corrected. (1) There were two quadrangle with MAPNAME = "CLINTON". The one on the Illinois-Iowa border was changed to "CLINTON IL-IA". (2) There was a value in the item USGS that contained a dash rather than a dot. This was corrected to conform with the correct format for this field. For detailed review see *path_name_suppressed*/quads_v1_0_rev.txt.
Attribute items are in typical ARC/INFO feature class format.
Those requiring additional explanation are:
POLYGON ATTRIBUTES:
MAPNAME - Name of the associated USGS 7.5 x 7.5-minute quadrangle
USGS - USGS map sheet index designation. This is an alphanumeric
combination of degrees north and west with a row column
index applied to each 1 degree by 1 degree area.
ARC ATTRIBUTES:
COORD - The latitude value for east-west arcs or the longitude
value for north-south arcs. Values are in decimal degrees.
COORD is redefined into two smaller fields:
INTEGER - The value of COORD to the left of the decimal.
(The value of COORD rounded down to a whole number.)
DECIMAL - The value of COORD to the right of the decimal.
(The incremental fraction of COORD.)
Q15 - Indicates if arc is also a boundary for a 15 minute quad.
0 - arc is not a 15 min. quad boundary
2 - arc is a 15 min. quad boundary
Q100 - Indicates if arc is also a boundary for a 30 x 60 minute quad.
0 - arc is not a 30 x 60 min. quad boundary
2 - arc is a 30 x 60 min. quad boundary
Q250 - Indicates if arc is also a boundary for a 1 x 2 degree quad.
0 - arc is not a 1 x 2 degree quad boundary
2 - arc is a 1 x 2 degree quad boundary
ANNOTATION ATTRIBUTES:
Each quad is annotated with the quad name diagonally from
southwest to northeast.
In no event shall the DNR have any liability whatsoever for payment of any consequential, incidental, indirect, special, or tort damages of any kind, including, but not limited to, any loss of profits arising out of use of or reliance on the geographic data or arising out of the delivery, installation, operation, or support by DNR.
Shift-click to download the data set and related documentation. (Data and metadata offered separately, please download both files.)
Illinois Natural Resources Geospatial Data Clearinghouse
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