USGS 7.5 Minute Topographic Maps (2000)

Originator: New York State. Department of Environmental Conservation. Division of Fish, Wildlife, and Marine Resources.
Publication_Date: 20000728
Title: USGS 7.5 Minute Topographic Maps (2000)
Geospatial_Data_Presentation_Form: map
Publication_Place: Albany, New York
Publisher: New York State. Department of Environmental Conservation.
Abstract: This data set consists of images derived from scans of U.S.G.S. 7.5 minute quadrangle maps (Digital Raster Graphics). The images form a set of seamless tiles, 5,000 m on a side, from which the map collar information was removed. Images are GeoTIFF files in NAD83, UTM zone 18.
Purpose: A DRG is useful as a source or background layer in a GIS, as a means to perform quality assurance on other digital products, and as a source for the collection and revision of DLG data.
Supplemental_Information: 1. Checking a sample of the DRGs produced by the U.S.G.S. indicated that the images were mis-registered by as much as 5 pixels (about 12 meters). Although the images were re-registered in an effort to reduce this error, perfect registration was not always possible. We found that some of the original images were scanned with distortion that could not be removed in the re-registration process. Thus, an unknown proportion of the images have errors which, when combined with any errors in the original maps, may exceed the limits of the National Map Accuracy Standards adhered to by the original maps. If a scanned image is to be used where accuracy at the 1:24,000 scale is needed, its registration accuracy should be verified. 2. The maps upon which the images are based used either metric contours in meters or English contours in feet. There is no easy way to determine which units are used for a particular image because the map collar information is not present. Users need to be aware of the need to use care in determining elevation units from these images. 3. For more background on Digital Raster Graphics, refer to the USGS. To identify codes used in the data go to <>, the Index of New York State Digital Raster Graph (DRG) Quad Names established by the USGS and NY Department of Transportation (DOT).
Beginning_Date: 1942
Ending_Date: 2000
Currentness_Reference: Ground Condition
Progress: Complete
Maintenance_and_Update_Frequency: Irregular
West_Bounding_Coordinate: -080.000000
East_Bounding_Coordinate: -071.875000
North_Bounding_Coordinate: +45.125000
South_Bounding_Coordinate: +40.375000
Theme_Keyword_Thesaurus: None
Theme_Keyword: Digital Raster Graphic
Theme_Keyword: DRG
Theme_Keyword_Thesaurus: LCSH
Theme_Keyword: New York (State).-- Dept. of Environmental Conservation.
Theme_Keyword: New York (State)--Maps, Topographic.
Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: imageryBaseMapsEarthCover
Place_Keyword_Thesaurus: LCSH
Place_Keyword: New York (State)
Access_Constraints: None
Use_Constraints: Acknowledgement of the USGS would be appreciated in products derived from these data.
Contact_Organization: New York State Department of Environmental Conservation
Contact_Person: Katherine Barnes
Address_Type: Mailing and physical
Address: 625 Broadway
City: Albany
State_or_Province: NY
Postal_Code: 12233-4754
Country: USA
Contact_Voice_Telephone: 518-402-8940

Logical_Consistency_Report: Not Applicable
Completeness_Report: The DRG is a faithfully reproduced digital images of the original source map. Some differences may be detected between the source graphic used and the DRG due to the RGB values assigned that particular color. The intent is to recreate those colors as near as possible. Data completeness for DRG files reflect content of the source graphic. Features may have been eliminated or generalized on the source graphic due to scale and legibility constraints. For information on collection and inclusion criteria, see U.S. Geological Survey, 1994, 24,000-Scale Digital Line Graphs and Natioal Mapping Program Technical Instructions and U.S. Geological Survey, 1994, Standards National Mapping Program Technical Instructions.
Process_Description: The 7.5 minute image files were copied from the distribution CDs to a disk drive. Images were selected for registration quality checking using a stratified random sampling scheme in which two non-adjacent maps were selected from each 1 degree block that was entirely within New York and one map was selected from each block that was partially within New York. This approximately 3% sample was evaluated by checking the neatline corners of the scanned map against a vector coverage of the quadrangle boundaries. Only three of the 47 sampled maps had neatline corners within one pixel of the vector boundaries. The remainder were mis-registered by between one and five pixels, equivalent to between 2.4 and 12 meters, in one or both directions. We decided, therefore, to re-register the images. Information on the evaluation process can be found in the report Evaluating DRG Image Registration Accuracy. Our ultimate goal was a set of images in UTM zone 18 in NAD83. A set of tests demonstrated negligible differences between the computationally time consuming process of projecting the images and projecting the coordinates of the upper left "placement" point in the ESRI world file. Theoretical considerations indicate little difference between projecting the image and using the ArcInfo GRIDWARP command to re-register the images because the NADCON grid spacing is 15 minutes. We decided to use GRIDWARP to perform datum conversion and re-registration at the same time. GRIDWARP was set up by creating links from the four corners of the image's map neatlines to a vector coverage of quadrangle boundaries. The vector coverage was derived from a coverage that had been generated in geodetic coordinates and projected to UTM Zone 18 in NAD27. For DRG re-registration this coverage was projected to NAD83 and the proper UTM zone for the quadrangle. Each image was converted to a grid, subjected to a first order (linear) GRIDWARP, and converted back to an image. The registration quality at the four corners was checked by a different person. The registration process was repeated if necessary until a good match was obtained between the raster and vector quadrangle corners. Eight quadrangles (o41076h5, o44074b8, o40073h2, k44073c7, k44073c5, o42073d7, k42073e3, o42073h7, o42079a1, and o42079a2) could not be successfully registered. Additional links were added for these files and they were registered with a second order GRIDWARP. Map collars were clipped from the images by extracting the zone and bounding geodetic coordinates for each quadrangle from the .fgd files that accompanied the images. This information was used to create a coverage that was projected from NAD27 to NAD83 in the proper UTM zone and used to clip a grid made from the image. The grids were then merged. Merging was automated for up to 48 images at a time. These grids were further merged. Grids with all quadrangles in UTM zones 17 and 19 were created and projected to zone 18. We attempted to create a single grid for the entire state but were unable to do so because the result would have exceeded the 2.1 GB size limit for a single grid. We therefore somewhat haphazardly merged the grids into larger grids. We then divided the state into six longitudinal zones. An outline coverage for each zone was created. All sides of these grids were oriented along the coordinate axes so that no areas of NODATA would be created when they were used to clip grids. Each outline coverage was then used to clip each of the larger merged grids. Finally, these clipped component grids were merged to grids that exactly filled a longitudinal zone. We created a coverage of polygons that were to be used to define the final image tiles. These polygons were squares of 5000 m oriented along the coordinate grid. The tiles were designed to coincide with the blocks used by the New York State Breeding Bird Atlas. The minimum X coordinate of the Breeding Bird Atlas coverage was projected to NAD83. This value was decreased by 20,000 and used as the starting coordinate in an ArcInfo GENERATE with FISHNET to produce square polygons 5000 m on a side. This coverage was then clipped by a polygon created by buffering a New York State outline coverage by 24,200 m. Labels were copied from the Breeding Bird Atlas coverage. Additional labels were added to the polygons that did not occur in the Breeding Bird Atlas coverage. These polygons were given a unique value for BLOCK, the item in the Breeding Bird Atlas coverage that identified each 5000 m square. The 5000 m square polygons were used to clip 5000 m square tiles from the longitudinal zone grids. Each 5000 m square polygon was extracted into a separate coverage. The minimum and maximum coordinates of this new coverage were determined. The maximum coordinates were incremented by 2.5, the approximate size of pixel, to deal with improper rounding in the ArcInfo GRIDCLIP command. These coordinates were then used as arguments to the Grid GRIDCLIP command with the BOX option to clip a 5000 m square tile out the longitudinal zone grid. This grid was then converted to an image with IMAGEGRID. Image file names were obtained by preceding the BLOCK item from the coverage PAT with "o" and converting the letter in BLOCK from upper case to lower case. An image catalog was created to manage the images. The AML FILELIST function was used to create a file that listed all the images. The name of this file was used as the argument in the ADDIMAGE command in order to populate the image catalog.
Process_Date: 19991231

Grid_Coordinate_System_Name: Universal Transverse Mercator
UTM_Zone_Number: 18
Scale_Factor_at_Central_Meridian: .9996
Longitude_of_Central_Meridian: -075.000000
Latitude_of_Projection_Origin: +00.000000
False_Easting: 500000
False_Northing: 0
Planar_Coordinate_Encoding_Method: row and column
Abscissa_Resolution: 2.5
Ordinate_Resolution: 2.5
Planar_Distance_Units: Meters
Horizontal_Datum_Name: North American Datum of 1983
Ellipsoid_Name: Geodetic Reference System 80
Semi-major_Axis: 6378137
Denominator_of_Flattening_Ratio: 298.257222101

Contact_Organization: Albert R. Mann Library
Address_Type: mailing and physical address
Address: Cornell University
City: Ithaca
State_or_Province: New York
Postal_Code: 14853
Contact_Voice_Telephone: 607-255-5406
Resource_Description: 7.5-minute digital elevation models; 7.5-minute DEM
Distribution_Liability: Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the accuracy or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. This disclaimer applies both to individual use of the data and aggregate use with other data. It is strongly recommended that careful attention be paid to the contents of the metadata file associated with these data. Neither the U.S. Geologial Survey nor the New York State Department of Environmental Conservation shall be held liable for improper or incorrect use of the data described and/or contained herein. Cornell University provides these geographic data "as is." Cornell University makes no guarantee or warranty concerning the accuracy of information contained in the geographic data. Cornell University further makes no warranty either expressed or implied, regarding the condition of the product or its fitness for any particular purpose. The burden for determining fitness for use lies entirely with the user. Although these files have been processed successfully on computers at Cornell University, no warranty is made by Cornell University regarding the use of these data on any other system, nor does the fact of distribution constitute or imply any such warranty.

Metadata_Date: 20060629
Metadata_Review_Date: 20060629
Contact_Organization: New York State Department of Environmental Conservation
Contact_Person: Katherine Barnes
Address_Type: Mailing and physical
Address: 625 Broadway
City: Albany
State_or_Province: NY
Postal_Code: 12233-4754
Country: USA
Contact_Voice_Telephone: 518-402-8940
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998