This feature dataset includes line and polygon feature classes for each of the following scales/extents: 3.75-minute x 3.75-minute, commonly called quarter-quadrangles, typically used for a 1:12,000-scale index, 7.5-minute x 7.5-minute, the common USGS topographic sheet extent, typically 1:24,000-scale in Illinois, 15-minute x 15-minute, typically used for 1:62,500-scale index, 30-minute x 1 degree, typically used for 1:100,000-scale index, 1-degree x 2-degree, typically used for 1:250,000-scale index.
Also included are master line, polygon, and corner point (tic) templates from which the above were generated. These are entitled Base_Template_Ln, Base_Template_Py and Corner_Tic_Pt respectively, and include of all the 3.75-minute x 3.75-minute quarter-quadrangles and corners from 36 to 43 degrees north latitude and 86 to 92 west longitude, with an indication of which are within Illinois.
Each boundary line is composed of segments that are 18 arc-seconds in length. To provide some reference, there are 25 such segments in a line 7.5 minutes long. These vertices are included so that on reprojection of the data into a different coordinate system the quadrangle boundaries will "curve" to maintain a realistic representation of quadrangle shape in relation to real world coordinates.
The data were generated as a mathematical construct, independent of ground condition. That is, they were generated from a digital file of decimal degree-minute-second locations for each quadrangle corner, using the ArcInfo Workstation GENERATE command. Tics were generated in this manner as well, one at each quarter-quad corner. Thus quadrangle corners are exact within ideal geographic decimal degree NAD83 coordinate space.
Some non-ideal quadrangle boundaries have been added to the dataset to account for quadrangle maps with irregular boundaries, for example 15-minute quadrangles in the Chicago area.
The nominal scale is as stated above for each feature class. However, these data are in fact scale-less because they are a mathematical construct independent of ground condition.
The spatial reference is the Geographic Coordinate System, decimal degrees, NAD83.
Recent updates to data:
In August, 2002 the name of the Eaton 7.5-minute quadrangle was updated to Porterville, to reflect an official name change by the Geographic Names Information System (GNIS).
Illinois State Geological Survey, 199803, USGS Quadrangle Boundaries and Corner Points in Illinois in NAD83: ISGS GIS Database GISDB.IL_QUAD_Usgs_Quadrangle_Index_Nad83, Illinois State Geological Survey, Champaign, Illinois.
This is a Vector data set. It contains the following vector data types (SDTS terminology):
Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.005. Longitudes are given to the nearest 0.005. Latitude and longitude values are specified in Decimal degrees.
The horizontal datum used is North American Datum of 1983.
The ellipsoid used is Geodetic Reference System 80.
The semi-major axis of the ellipsoid used is 6378137.000000.
The flattening of the ellipsoid used is 1/298.257222.
GIS Processing: ISGS staff and other staff of the Illinois Scientific Surveys. Documentation: ISGS and INHS staff Quality Control: INHS and ISGS staff
These data are most useful as indices and reference grids of quadrangle-based data, such as DOQs, DRGs and topographic map sheets. They have many applications in data cataloging and searching applications. These data also provide exact quadrangle corners in NAD83, which are useful for the registration of multiple quadrangle-based data layers.
These data are appropriate for use in local and regional thematic analysis. The data are not appropriate as a geodetic, legal or engineering base. The data set was not and is not intended as a substitute for surveyed locations, such as can be determined by a registered Public Land Surveyor. Although useful in a GIS as a reference base layer for maps, the data set has no legal basis in the definition of boundaries or property lines.
This data set was used to generate updated arcs and tics for coverages QUAD75, QUAD15, QUAD100, and QUAD250. Lines in the line feature classes were UNSPLIT based on the coordinate values to create a single, complete line segment for each side of a quadrangle.
Lines and polygons intersecting the state of Illinois were determined using a spatial join with the state boundary polygon in ArcView 3.2.
Other attribute data were transferred using spatial joins between legacy coverage label points and newly generated coverage polygons. The source legacy coverages are from the 1996 Illinois GIS CD-ROM compilation. The source legacy coverages date back to the mid-1980s and were originally developed as a part of a project known as the Illinois Geographic Information System (IGIS).
AML to generate tics and lines:
&mess &off &sv ticid = 0 &sv arcid = 0
&sv inc = 625 &sv minlat = 360000 &sv maxlat = 430000 &sv minlon = 870000 &sv maxlon = 920000
&mess &on &type Calculating coordinates for arcs and tics... &mess &off
&sv open1 = [open tics.txt opens -write] &sv open2 = [open arcs.txt opens -write]
&do lat = %minlat% &to %maxlat% &by %inc% &do lon = %minlon% &to %maxlon% &by %inc%
&sv lat1 = %lat% / 10000 &sv lon1 = %lon% / -10000
&sv lat2 = ( %lat% + %inc% ) / 10000 &sv lon2 = ( %lon% + %inc% ) / -10000
&sv ticid = %ticid% + 1 &sv writeline %ticid%,%lon1%,%lat1% &sv wrote [write %open1% %writeline%]
/*&sv arcid = %arcid% + 1 &sv arcid = %lon% &sv wrote [write %open2% %arcid%] &sv writeline %lon1%,%lat1% &sv wrote [write %open2% %writeline%] &sv writeline %lon1%,%lat2% &if ^ %lat% = %maxlat% &then &sv wrote [write %open2% %writeline%] &sv writeline end &sv wrote [write %open2% %writeline%]
/*&sv arcid = %arcid% + 1 &sv arcid = %lat% &sv wrote [write %open2% %arcid%] &sv writeline %lon1%,%lat1% &sv wrote [write %open2% %writeline%] &sv writeline %lon2%,%lat1% &if ^ %lon% = %maxlon% &then &sv wrote [write %open2% %writeline%] &sv writeline end &sv wrote [write %open2% %writeline%]
&sv writeline end &sv wrote [write %open1% %writeline%] &sv wrote [write %open2% %writeline%]
&sv closed [close -all]
&mess &on &ret
After generating the coordinate files with this AML, arc and tic coverages were manually generated with the GENERATE command and then manually combined in ArcEdit 7x.
Person who carried out this activity:
The data were then imported into an SDE feature dataset. At this point the edition number was updated to 2.0 to reflect the significant change in data storage model.
Person who carried out this activity:
Person who carried out this activity:
[begin excerpt from GNIS statement]
In the case of the Porterville issue, this geographic feature (the place) was named Eaton. The name Eaton came from the establishment of the original Post Office there and it's Postmaster John Eaton in 1852. The indication of the post office Eaton is shown on the USGS map with a parenthetical under the name Porterville, though the Post Office no longer exists.
This name case is a BGN OSN - Board on Geographic Names Official Standard Name, which means it was visited by the BGN Staff but was approved by an Administrative Authority; it did not go to a full board vote. The place was originally platted as East Berlin, but there was little growth until 1850 when Richard Porter established a Blacksmith Shop there. Porterville is the more widely accepted name for the community, though it is also known as Eaton. So this change mandated the change to the USGS quad, after it was brought forward as a possible controversy by our Mapping Center (Rolla) during a project in IL dated 07/01/83.
Person who carried out this activity:
Illinois State Geological Survey, 199803, USGS Quadrangle Boundaries and Corner Points in Illinois in NAD27: ISGS GIS Database GISDB.IL_QUAD_Usgs_Quadrangle_Index_Nad27, Illinois State Geological Survey, Champaign, Illinois, USA.
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, Policy on Appropriate Use of Computers and Network Systems at the University of Illinois at Urbana-Champaign.
No formal review has been completed. Regular use of these data, however, indicate attributes are accurate.
These data are a mathematical construct and as such should have a high degree of positional accuracy (i.e. exact, with the exception of arcs added for irregular 15-minute quadrangle boundaries). No review has been completed, however. There have been several instances where map indices generated from these boundaries have been used with other data digitized from USGS quadrangles with good results.
This dataset includes all of the 3.75-minute x 3.75-minute quarter-quadrangle boundaries and areas from 36 to 43 degrees north latitude and 87 to 92 west longitude, with an indication of which intersect Illinois. This includes quadrangle corner coordinates.
Line and polygon feature classes for each of the following scales/extents can, and have been, constructed: 3.75-minute x 3.75-minute, commonly called quarter-quadrangles, typically used for a 1:12,000-scale index 7.5-minute x 7.5-minute, the common USGS topographic sheet extent, typically 1:24,000-scale in Illinois 15-minute x 15-minute, typically used for 1:62,500-scale index 30-minute x 1 degree, typically used for 1:100,000-scale index 1-degree x 2-degree, typically used for 1:250,000-scale index
There are two additional arcs in the Chicago region form the eastern boundaries of two irregularly shaped 15' quadrangles. These have values of 999 and 0.999 in the INT_COORD and DEC_COORD fields respectively.
A logical consistency review was performed in March, 1998. At that time the data were maintained in ArcInfo coverage format.
The following checks were made:
The 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 attribute items, requirement of all unique values for an item, logic of items redefined over other items, and length of item name as regards conversion to shapefile format.
The topology status of the data set was checked, as were LABELERRORS, NODEERRORS (if appropriate), and the PROJECTION definition.
The presence of a BND file was verified.
The presence and location of TICS were checked.
Polygon and chain-node topology were present. There were no dangling arcs. There was one polygon label per polygon, except for the universe polygon. Boundary values were appropriate for the map projection and map units. COVER-ID values were recalculated to be unique. See the process step for March, 1998.
There are two additional arcs in the Chicago region form the eastern boundaries of two irregularly shaped 15' quadrangles. These have values of 999 and 0.999 in the INT_COORD and DEC_COORD fields respectively. There are no known attribute values outside the appropriate domains.
Are there legal restrictions on access or use of the data?
- ISGS information must be obtained directly from the ISGS or from an authorized distributor. Be aware that ISGS information obtained from an unauthorized third party may have been altered subsequent to original distribution, or may no longer be current.
Links to these are provided in the Cross References section.
- ISGS information is the property of and copyrighted by the Board of Trustees of the University of Illinois with all rights reserved. University copyright policy is stated in the General Rules Concerning University Organization and Procedure, Article III, Section 4. A link is provided in the Cross References section.
Individuals or entities may make fair use of copyrighted ISGS material, such as reproducing a single figure or table, or using a brief text quotation, without obtaining formal permission, but in all cases the Illinois State Geological Survey must be credited as the source of the material. To reproduce ISGS information beyond the fair use standard, permission must be obtained from the ISGS Information Office, 615 East Peabody Drive, Champaign, Illinois 61820, 217-333-4747, firstname.lastname@example.org. License fees and a license agreement may be required, depending on the proposed usage.
Map information is to be used at a scientifically and cartographically appropriate scale, that is, at a scale no greater than indicated on the map or as described in the documentation of the map or map data. Map information is not appropriate for, and is not to be used as, a geodetic, legal, or engineering base. Map information has no legal basis in the definition of boundaries or property lines and is not intended as a substitute for surveyed locations such as can be determined by a registered Public Land Surveyor.
The data do not replace the need for detailed site-specific studies.
Disclaimer of Liability Disclaimer of Warranties and Accuracy of Data Disclaimer of Endorsement Disclaimer for External Links Disclaimer of Duty to Continue Provision of Data Security Choice of Law
The data are intended for use with GIS software. The ISGS uses ESRI ArcGIS software, however, ESRI formats can be imported into many different GIS software packages. It is expected that customers who obtain these data have the technical expertise to use GIS software. The ISGS does not provide software support of any kind.
Illinois Natural Resources Geospatial Data ClearinghouseGenerated by mp version 2.8.25 on Thu Apr 02 09:54:10 2009