FINAL REPORT - International Joint Commission

ANNEX 2
Figure I-4: South Colwell Pond (New York) color infrared photograph
GIS Standards Development
The Study Board established geographic information system (GIS) standards in the first year of the Study.
The initial standards were developed for the following:
• Characteristics of base maps
Base layers include standard topographic and planimetric information usually portrayed on a map.
Topographic data include elevation contours, spot heights, and shorelines. Planimetric data include
roads and streams as well as administrative and political boundaries.
• Map Projections
Map projections are used to portray a portion of the Earth on a flat surface. Some distortions of
conformity, distance, direction, scale, and area always result from this process. A Lambert Conformal
Conic projection with associated attributes was selected for use for all study geospatial datasets.
• Horizontal and vertical control datums to be used
Geodetic datums define the size and shape of the Earth and the origin and orientation of the coordinate
systems used to map it. The Study used the NAD 83 horizontal datum with the GRS 80 ellipsoid.
Two common vertical datums for North America were used in the Study, the North American Vertical
Datum of 1988 (NAVD 88) and the International Great Lakes Datum of 1985 (IGLD 85).
• Measurement units
Since Canada and the U.S. use different measurement systems, it was decided that all data would be
in metric units.
148 Options for Managing Lake Ontario and St. Lawrence River Water Levels and Flows