U.S. Geological Survey
Unknown
Unknown
Digital Elevation Models (DEM) - New York State
Reston, VA
U.S. Geological Survey
http://cugir.mannlib.cornell.edu/datatheme.jsp?id=23
A Digital Elevation Model (DEM) contains a series of
elevations ordered from south to north with the order of the
columns from west to east. The DEM is formatted as one ASCII
header record (A-record), followed by a series of profile
records (B-records) each of which include a short B-record
header followed by a series of ASCII integer elevations per each
profile. The last physical record of the DEM is an accuracy
record (C-record). The 7.5-minute DEM (10- by 10-m data spacing,
elevations in decimeters) is cast on the Universal Transverse
Mercator (UTM) projection (the quads UTM zone can be found in
the header record (Record A)) in the North American Datum of
1927. It provides coverage in 7.5- by 7.5-minute blocks. Each
product provides the same coverage as a standard USGS 7.5-minute
quadrangle, but overedges are published as separate DEM files.
Coverage is available for all quads completely contained within
New York State, plus some additional ones falling along the
borders and containing significant area of the State's land.
DEMs can be used as source data for digital orthophotos and
as layers in geographic information systems for earth science
analysis. DEMs can also serve as tools for volumetric analysis,
for site location of towers, or for drainage basin delineation.
These data are collected as part of the National Mapping
Program.
7.5-minute DEMs have rows and columns which vary in length
and are staggered. The UTM bounding coordinates form a
quadrilateral (no two sides are parallel to each other), rather
than a rectangle. The user will need to pad out the uneven rows
and columns with blanks or flagged data values, if a rectangle
is required for the user's application. Some software vendors
have incorporated this function into their software for input of
standard formatted USGS DEMs.
unknown
ground condition
Irregular
-79.77
-71.85
45.02
40.49
None
digital elevation model
digital terrain model
hypsography
altitude
height
landforms
relief
topography
raster
grid
cell
Library of Congress Subject Headings
Hydrography
Digital Mapping
Digital mapping -- Automation
Cartography -- Automation
New York (State) -- Dept. of Environmental
Conservation
ISO 19115 Topic Category
elevation
006
Department of Commerce, 1987, Codes for the
Identification of the States, The District of Columbia and
the Outlying Areas of the U.S., and Associated Areas
(Federal Information Processing Standard 5-2): Washington,
Department of Commerce, National Institute of Standards and
Technology (http://www.itl.nist.gov/fipspubs/fip5-2.htm)
New York
36
NY
Library of Congress Subject Headings
New York (State)
Geographic Names Information System
http://geonames.usgs.gov/pls/gnispublic
New York State
None
1. The NYS DEC and the U.S. Geological Survey asks to be
credited in derived products. 2. Secondary Distribution of the data
is not allowed. 3. Any documentation provided is an integral part of
the data set. Failure to use the documentation in conjunction with
the digital data constitutes misuse of the data. 4. Although every
effort has been made to ensure the accuracy of information, errors
may be reflected in the data supplied. The user must be aware of
data conditions and bear responsibility for the appropriate use of
the information with respect to possible errors, original map scale,
collection methodology, currency of data, and other conditions.
New York State Department of Environmental
Conservation. Division of Water
Watershed Geographic Information Technologies Support
Group, Chief
mailing and physical address
625 Broadway
4th floor
Albany
New York
12233-3500
518-402-8259
watergis@gw.dec.state.ny.us
All questions regarding metadata and/or data should go
through the internal DEC contact.
24,000 scale hypsographic contour linework drawn by
photogrametric, plane table or other methods by USGS, US Army Corp
of Engineers, Tennessee Valley Authority or others. Linework copied
onto stable-base mylar. Raster image of linework created by USGS,
Reston, with Optronics drum scanner at an aperture of 20um, to give
an equivalent resolution of 1024 DPI. Raster data converted to
vector with line-center algorithm in LT4X v. 3.1, 11/11/93, by John
Dabritz of Infotec Development Inc. Grid elevations calculated with
8-profile weighted linear interpolation, with cubic smoothing of
slope at the contour line as per algorithm in above mentioned LT4X
v. - export in DEM format, UTM meters, - grid height and width of 10
mt, - clipping (overedge) coordinate in UTM mt, - input coord feet
or meters (depending on source material), output in
meters/decimeters, - DEM grid points which are on a profile section
longer than 80 mt are smoothed by passing the grid through a low
pass-filter twice. The filter size (see below) is of 9 cell
diameters (aprox 9 mt). The purpose here is to leave well-contoured
areas untouched while smoothing areas of less than 5-2.5% slope (to
lessen streaking in flat areas typical of multiple-profile DEM
derivation). - cubic smoothing of elevation profile across contours
to 35% of the distance between adjacent contours. These profiles
have a smaller, but still discontinuous change in slope at contour
intersection than if not rounded. - 9 cell diameter for smoothing
reach, - use all 8 directions (from grid point to N, S, E, W ,NE,
NW, SE, SW) for each cell, - no line feeds. export dem
<contour data name> 2 10.00 10.00 2 1 4 80 2 0.35 9 8
0
US Geological Survey
unknown
Digital Elevation Model (DEM)
http://eros.usgs.gov/guides/dem.html
10 mt gridding cell spacing is the maximun that can be
meaningfully extracted from hypsography contour lines. This
allows very good hypsographic contour reproduction in all areas
except very flat ones. Elevation_resolution_ is 1 decimeter (0.1
meter). Elevation accuracy is 24,000 contour data, i.e.
plus/minus half the contour interval.
The fidelity of the relationships encoded in the data structure
of the DEM are automatically verified using a USGS software program
upon completion of the data production cycle. The test verifies full
compliance to the DEM specification.
DEM visually inspected using Delta3D version 2.0, 1995 by John
Dabritz and S. Phan of Infotec Development Inc. Checked for
completness and drainage characteristics matching the USGS
Hydrography Digital Line Graphs published at the same time as the
model. Further validation for logical consistency performed previous
to submission for archiving.
The horizontal accuracy of the DEM is expressed as an
estimated root mean square error (RMSE). The estimate of the
RMSE is based upon horizontal accuracy tests of the DEM
source materials with equal to or less than intended
horizontal RMSE error of the DEM. The testing of horizontal
accuracy of the source materials is accomplished by
comparing the planimetric (X and Y) coordinates of
well-defined ground points with the coordinates of the same
points as determined from a source of higher accuracy.
3 meters (estimated)
Digital elevation models meet horizontal National
Map Accuracy Standards (NMAS) accuracy
requirements.
A vertical RMSE of one-half of the contour interval of
the source map is the maximum permitted. Systematic errors
may not exceed the contour interval of the source graphic.
Level 2 DEMs have been processed or smoothed for consistency
and edited to remove identifiable systematic errors.
6 to 8 meters
DEMs meet vertical National Map Accuracy Standards
(NMAS) accuracy requirements. Vertical Positional
Accuracy Vaue varies with each quad.
U.S. Geological Survey
Unknown
Unknown
Albany
EROS Data Center, SD
U.S. Geological Survey
mylar separate from original color separation plate
unknown
ground condition
CONTOUR1
elevation values for interpolation
U.S. Geological Survey or National Geodetic
Survey (NGS) (ed.)
Unknown
Unknown
project control
EROS Data Center, SD
U.S. Geological Survey
field notes
unknown
ground condition
CONTROL1
ground control points
U.S. Geological Survey (ed.)
Unknown
Unknown
photo ID number
EROS Data Center, SD
U.S. Geological Survey
transparency
unknown
ground condition
PHOTO1
elevation values from photogrametry
The process can be seen as divided into several tasks,
each with associated sub-processes. A. Original Data Source
Preparation: 1. The United States Geological Service (USGS)
office of Map Production (Mid Continent Mapping Center,
Rolla, MO) selects the most recent original printing plates
(1:24,000 or 1:25,000 scale) for each published quadrangle
map. These plates are archived under controlled
environmental conditions and are produced from the original
map scripting materials onto dimensionally stable material
(Mylar). A copy of the separate is made by contact methods
onto photosensitive, opaque, dimensionally stable material.
The separate plate copy is shipped to the USGS Mapping
Applications Center (Reston, VA). 2. The MAC scans the
separate plate with an Ektaprint (a.k.a. Optronics) drum
scanner with an aperture of 24um (corresponding to a linear
resolution of approx 1030 DPI) into a run-length encoded
(RLE) formatted raster file. Contours lines have typically a
thickness of 25 to 30 pixels. The file, typically between 10
and 20 Mb, would be checked for completeness and distortion.
If satisfactory MAC forwards both the raster file, the plate
separate and the corresponding published quadrangle to the
digitization workshop at the New York State Department of
Environmental Conservation Water GIS unit in Albany, NY. B.
Raster file batch processing 1. The raster file was loaded
into Line Tracer for X Windows (LT4X, Infotec Inc.,
Portland, Oregon) version 3.1. With it is georegistered and
trimmed of any excess margin. 2. The file is put through an
automated raster-to-vector batch process in which a vector
following the center of the raster line is created, with a
minimum vertex separation of 25 pixels. Once the vector has
been calculated and the topology of the resultant data
established, the resolution of the original raster was
reduced to 500 DPI, to allow faster processing in the
succeeding steps. C. Vector Contour Edit, Edge Matching and
Labeling. 1. The vectorized contours are edited carefully to
correct any line breaks, vector webbing (due to pen
thickness or lack of resolution of the original's drafting
process), labels and special line symbols (depressions, road
fills, etc). 2. The contours are labeled with their
corresponding elevations, as tagged in the original
material. 3. The eight adjoining maps' vector contours are
brought in and checked against those of the map being
edited. Vectors of matching labels are snapped together if
the gap is less than 3 line-thicknesses. Otherwise they are
tagged as "disagreement in the original" (see DLG standards
for hypsography layer). For each border only one of the maps
is edited. 4. An independent quality control check of
contour edits and labeling is carried out. 5. The Digital
Elevation Model is interpolated in a batch process (see
"Native Dataset Environment" above). D. DEM Edit and Quality
Control 1. The resultant DEM is loaded in Delta3D (Infotec
Inc., Portland, OR) v. 2.1, together with the corresponding
hydrography vectors. The DEM is checked for the presence of
irregular patterns, in which case it is returned to the
previous process; water body height (e.g. in large lakes) is
set for all grid cells within the water body; and drainage
along vector streams is enforced by lowering cells higher
than the upstream one along the stream. Water retention
areas (wetlands, marshes...) are not modified except for
stream entrance and exit. - Edge matching with the adjoining
eight DEMs. 2. From thirty to thirty-five height reference
markers are collected from the corresponding cultural
separate for the quadrangle. These are compared to heights
as read from the DEM and an statistical RMS is calculated,
this is recorded in the DEM's C record. 3. The quadrangle
record A is filled and checked for consistency. 4. A final
DEM-formatted elevation dataset for the quadrangle is
recorded. E. Final Quality Control and Databasing 1. The DEM
file is shipped to USGS's Rocky Mountain Mapping Center
(Boulder, CO). There it undergoes a separate quality control
process which essentially mimics D. 2. The corresponding
quality control flags are established. The DEM is
sub-sampled to 30 mt grid spacing and the resultant file is
forwarded to USGS's EROS Data Center, were it is catalogued
into the National Elevation database. The 10 mt grid spacing
file is returned to NYS DEC, from where it is forwarded to
Cornell University's Mann Library.
Unknown
row and column
10
10
Meters
North American Datum of 1927
Clarke 1866
6378206.4
294.9787
National Geodetic Vertical Datum of 1929
1
decimeters
Explicit elevation coordinate included with horizontal
coordinates
The digital elevation model is composed of an elevation
value linked to a grid cell location representing a gridded form
of a topographic map hypsography overlay. Each grid cell entity
contains an 8-character value between -32,767.0 and 32,768.0.
U.S. department of the Interior, U.S. Geological Survey,
1992, Standards for digital elevation models: Reston, VA, a
hypertext version of the Digital Elevation Model (DEM) is
available at: http://eros.usgs.gov/guides/dem.html (see Cross
Reference)
Hillshade_USGS_CUGIR_Region.tif.vat
Table
248
OID
OID
OID
4
0
0
Internal feature number.
Esri
Sequential unique whole numbers that are automatically generated.
VALUE
VALUE
Integer
10
10
0
COUNT_
COUNT_
Integer
10
10
0
Mann Library
mailing
Cornell University
Ithaca
NY
14853
USA
607-255-5406
mann_ref@cornell.edu
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.
DEM
zip
http://cugir.mannlib.cornell.edu/datatheme.jsp?id=23
None
20080414
20080414
New York State Department of Environmental
Conservation
Division of Information Services; GIS Unit
mailing and physical address
625 Broadway
3rd floor
Albany
New York
12233-2750
518-402-9860
518-402-9031
enterpriseGIS@gw.dec.state.ny.us
FGDC Content Standards for Digital Geospatial Metadata
FGDC-STD-001-1998
Esri ArcGIS 13.0.3.36057
Hillshade_USGS_CUGIR_Region.tif
1
-75.386459
-73.744480
42.384751
41.243050
Hillshade_USGS_CUGIR_Region.tif
002
252635.190869
696236.665869
878944.445810
1293740.204143
1
Projected
GCS_North_American_1983
Linear Unit: Foot_US (0.304801)
NAD_1983_StatePlane_New_York_East_FIPS_3101_Feet
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