Abstract: This shapefile contains polygons representing the historical
land cover within the watersheds near Sandy Pond, in New York, on the
eastern shore of Lake Ontario. These land cover boundaries and types
were interpreted from aerial photos dating from 1938.
Purpose: To evaluate broad changes in land cover over time.
Supplemental_Information: This dataset was developed as part of the Lake Ontario
Biocomplexity Project. For more information, see:
Browse_Graphic_File_Description: preview of the dataset
Completeness_Report: The maps for the historical time periods (1938, 1955, and 1975)
are not spatially complete. In all cases the shoreline is most complete
but watershed coverage is spotty. North and South Sandy Pond watersheds
and South Colwell watershed are represented in part or in full for some
years. Floodwood watershed is not represented in any of the historical
years. This is because Floodwood and South Colwell are in Jefferson and
Lewis Counties. We were unable to locate any historical photos for these
counties from any federal, state, or local agency. Private firms were also
dead ends for locating historical photos and the NY Office of Real
Property Services who purported to have some historical coverage would not
allow our project to use their photos. Oswego County had good coverage
though in some years even it was not continuous and hence the sometimes
incomplete maps for N and S Sandy Ponds. For the purposes of historical
analysis for the Biocomplexity project the shorelines and some of the
subwatersheds (for which we do stream sampling) can by viewed in their
Horizontal_Positional_Accuracy_Report: It is important to note that the aerial photos used for this
project differed in resolution, scale, and distortion. Therefore the
level of detail within each of the landcover maps varies.
Additionally, due to this distortion the resulting maps do not align
perfectly at boundaries such as shorelines and embayments and even
fixed objects. The project group took as much care as possible to get
good registration, and achieved the best possible without advanced
triangulation and other interpretation techniques that were beyond the
scope of this project. Users of these maps should be aware of these
limitations and use them as general depictions of the land use and
land cover and use them to only evaluate broad changes over time.
Process_Description: Files were created by aligning historical aerial photographs
along flight lines and tracing landcover classes onto clear acetate
overlays. The polygons on the overlays were then digitized into
ArcView GIS in Sibley Hall at Cornell during the Summer of 2003 by our
REU intern, Seth Lozano. Interpretation of the aerial photos was done
by Seth, Andrea Parmenter, and the rest of the summer field interns.
All photos for the project were provided by the Oswego County Soil and
Water Conservation District in Fulton, NY. (One exception to the above
protocol was for the 1995 land cover. For this time period the Digital
Orthophoto Quarter Quadrangles in near infrared were printed at a
scale of 1:24,000 and the acetate laid on top of them. These DOQQ's
are available for free online from the NY State GIS server and are
considerably more detailed than any other photos used in the study.
They are also more spatially accurate in terms of georeferencing.
Therefore, we believe this map to be the most accurate of any in the
eight watersheds. It is also the only spatially complete map in the
eastern study sites containing the Floodwood watershed. The DOQQ
photos exist in UTM, Zone 18, NAD83. We digitized the overlays from
the DOQQ's by registering them to tics in this same Datum. The final
map was then projected to UTM, Zone 18, Datum NAD27 to match the
others in the study.) Registration of the acetate overlays to real
world coordinates was accomplished by using a series of tic marks
(e.g. road intersections for which we knew the coordinates and could
locate on the photos). In all cases care was taken to minimize the
root mean square (RMS) error, and hence distortion caused by registration.
The RMS values and tic IDs used for each map can be found in the red
airphoto documentation notebook in 306 Rice Hall.
Process_Description: CUGIR staff defined the dataset projection as UTM18N (meters,
NAD27), removed extraneous attributes, and exported the data as a
Distribution_Liability: 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.