This GIS dataset portrays the distribution of glacial landforms within the Calgary-Lethbridge Corridor area, based on the compilation of existing government survey mapping and research literature, supplemented by new analysis of remote sensing data. The original line features have been modified where necessary for map production at 1:250 000 scale.
This dataset contains the line features of Alberta Geological Survey Map 579, Surficial Geology of the Calgary-Lethbridge Corridor, and has been exported in a shapefile format for public distribution.
Digital versions of existing maps were combined with new mapping data and digitization of existing maps for which digital versions were unavailable to produce a single GIS dataset with complete coverage of the Calgary-Lethbridge Corridor study area. We processed the data as follows:
1. Existing digital data from previously published maps were combined into a single GIS dataset. These features were classified according to a uniform map legend;
2. Maps and figures for which digital data were unavailable were scanned and georeferenced. Line features on these maps were then digitized and classified according to the uniform map legend;
3. A digital elevation model (DEM) dataset was assembled, consisting of shaded-relief images produced from 5 m resolution, bare-earth LiDAR DEMs. Areas of the province currently without LiDAR coverage were supplemented by shaded relief images produced from the Alberta Environment and Parks (AEP) DEM;
4. Multiple shaded-relief images from differing light source directions were generated in areas exhibiting a complex linear landform assemblage, using both the LiDAR data and AEP DEM. These images were reduced into a three-band image using principal components analysis (PC1, PC2, PC3) to eliminate any potential directional bias in the visibility of linear features;
5. The compiled glacial landform digital data were overlain on the LiDAR DEM and/or AEP DEM to confirm whether they had any distinct topographic expression. Any inconsistencies in previous mapping and classification were either corrected, or if hypothesized features exhibited no topographic expression, they were not included in this dataset. In areas where compiled line features occurred as closely spaced or segmented lines, individual lines were selectively removed;
6. Additional data sources, consisting of reports and published research papers were consulted, scanned and georeferenced where appropriate. Because much of the data in these sources were presented as small-scale figures, these sources of information were used as a guide for delineating additional landforms by using the LiDAR and/or AEP DEM to re-trace the previously identified landforms where visible on our imagery sources;
7. New digitization of landforms was performed where necessary, using the LiDAR DEM and/or AEP DEM.