1. Image Rectification of Three Niagara River Islands
Spencer Podsiadlo, GEG 418 (518), Tao Tang, Department of Geography and Planning
Buffalo Niagara Riverkeeper is completing a project called the Niagara
River Greenway Habitat Conservation Strategy. One thing they would like
to do is characterize loss of island habitat within the river over time. The
challenge of this project is not the acreage change itself but first obtaining
and properly aligning current satellite images with older images so that the
acreage change analysis can be done.
What was first needed were current satellite images which were obtained
from the New York GIS Clearing House site. This site contains a page with
an interactive map where you can zoom in to a particular area and
download the satellite images. By current that means the images came
from 2011.
Next images from 1978 and 1927 were obtained from a page on the
University of Buffalo’s website. Current and historic images were collected
for Buckhorn Island, Luna Island and Three Sisters Islands.
Finally the 2011 images for each island were rectified to the 1978 and 1927
images. This is because the historic images do not have a coordinate
system so doing the acreage change analysis would be invalid if all images
were not using the same coordinate system which is NAD 1983 State
Plane New York West.
Methods or Approach
Introduction
References
Interpretation of Findings
Conclusions
Results
Acknowledgements
Top: Buckhorn 2011.
Bottom: Three Sisters and Luna 2011.
Clockwise from top left: Buckhorn 1927, Buckhorn 1978, Three Sisters and
Luna 1978, Three Sisters and Luna 1927.
The images were successfully rectified with some possible error. The process is not
perfect. Not everything will line up between two images but this is better than
attempting to compare an image with a coordinate system to one without a coordinate
system.
The rectification process for Buckhorn Island, rectifying the 1978 image to the 2011 image.
In general all images for each island and time period line up correctly. There
will of course be some error due to poor image quality thus making the
process of placing control points difficult. Particularly when comparing
Buckhorn images from 1927 and 2011. The landscapes are vastly different
and so identifying physical features where control points could be placed
became complicated.
Three Sisters and Luna Islands post-rectification with the 2011 image
on top and the 1978 image beneath it.
This project is only a portion of a larger project to complete
acreage change of these islands for the Buffalo Niagara
Riverkeeper’s restoration project.
Without completing this step and applying the NAD 1983 State
Plane New York West coordinate system to the historic images,
measurements of distance and area could not be conducted
properly.
Others may be interested to use this process if specific
measurements must be completed for an image with no
coordinate system assigned to it.
Current satellite images are digital orthographic aerial
photographs from New York GIS Clearing House site.
NYS GIS Clearinghouse
http://gis.ny.gov/
Qiao, Jundong. (2014) “Acreage of Island Habitat in Upper Niagara River
Compared to Historic”. Buffalo State College, CIE 507 GIS Class
Project. May, 2014.