Extent of Canada's wetlands indicator: data sources and methods, chapter 4


4. Methods

The contributing datasets use varying methodology to identify wetlands, although most are based on remotely sensed data. Wetlands are mapped as vector data, which are integrated into a master geodatabase at the national scale.

Information from each contributing dataset was classified based on the Canadian Wetland Classification System,Footnote [1] which contains five main wetland classes (bog, fen, marsh, swamp, and shallow water) that represent the types of wetlands encountered in Canada. An additional category, "partially classified," was used to preserve boundary information for wetlands that could not be classified into the main categories with existing information.  

Where two or more datasets overlapped, the best dataset was selected based on the quality of collection methods and the accuracy of the data. Not all datasets had known accuracy. In these cases, accuracy was assessed by comparing a sample of wetlands polygons to Landsat imagery.

The national wetland layer contains wetland data compiled from the best available data layer for each region, classified by wetland type.

To produce the wetland map, the proportion of wetland in a 25 km by 25 km grid was calculated using ArcGIS software. These proportions were mapped as density classes using previously defined thresholds.Footnote [2]

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