High resolution digital elevation models are available
for the State of New York including Long Island. These have a horizontal
resolution of 10 meters and are based on
7.5' topographic maps. For those quadrangles with 10' contour intervals, interpolation results in
elevations with an uncertainty of about 4'. The appearance is as
if one were viewing color-enhanced images of a barren terrain, for
example Mars. This allows one to see much greater detail than is possible on
a standard topographic map. The images shown on this web site have a much lower
resolution than are obtainable from the files directly.
Digital
Elevation Models for Long Island and surrounding area can be downloaded as self
extracting zip files at http://www.geo.sunysb.edu/reports/dem_2/dems/
A ca. five foot long version (jpg) of the DEM of Long Island (see
above except with scale and north arrow) for printing can be downloaded
at this link. The file is 7 MB, so
be patient.
A DEM of Long Island (shown above) in PowerPoint can be downloaded
at this link.
The geomorphology of Long Island has been evaluated earlier
based on US Geological Survey topographic maps (see for example, Fuller, 1914;
and Sirkin, 1983). Most of the observations presented here are consistent with
previous interpretations. Reference to earlier work is made mainly where there
is a significant disagreement based on the higher quality of the information
obtainable from the DEM's. Also, it is intended that this presentation encourage
others to download DEM files and re-evaluate the geology and geomorphology of
other areas on Long Island. It is also hoped that this presentation will
encourage others to look for more information that will substantiate or negate
some of the interpretations presented here, i.e., test the hypotheses
presented. If you have any questions or comments on this presentation, send them
to gilbert.hanson@sunysb.edu. If
you wish, the comments or enhancements may be added to this web site. This
presentation will continue to be considered a work in progress.
This presentation gives a short overview of the geology and
geomorphology of Long Island with a more detailed description of the Stony
Brook-Setauket-Port Jefferson area. The
geomorphology is re-evaluated from 7.5' quadrangle Digital
Elevation Models (DEM) files created by the USGS from USGS 7.5 minute quadrangle
topographic maps with a pixel spacing of 10 meters. Each pixel has longitudinal, latitudinal and
elevation characteristics.
These maps were originally downloaded from the
Cornell University Geospatial Information Repository (CUGIR).
CUGIR is an active online repository providing geospatial data and
metadata for New York State. The data images were created in
Global Mapper. dlgv32
Pro is a free limited-feature version of the commercial software Global
Mapper that can be downloaded at
http://mcmcweb.er.usgs.gov/drc/dlgv32pro/
These images show elevation as a function of color and shading as if the sun
were shining on the surface (shaded relief). Relief can be variably exaggerated and the colors
can be adjusted. Also, culture is not included in the DEM's. Culture on standard
quadrangle maps makes
interpreting the geology more difficult.
Surprisingly few features that are clearly a result of human activity are
discernible in the DEM's. Railroads, highways and gravel pits can sometimes be
identified.
Another
program for viewing DEM files is MicroDEM a very capable viewing and analyzing
DEM tool. MicroDEM was developed by Peter Gauth of the US Naval Academy. The web
site describing MicroDem and where you can download this program for free
is at
http://www.usna.edu/Users/oceano/pguth/website/microdemdown.htm
There is a sharewareMac program for viewing DEM files (MacDEM) that
can be downloaded at:
http://www.treeswallow.com/macdem/
You may wish to visit
GeoCommunity
which has listings of programs that can be used for GIS or DEM
viewing. |