Data Acquisition and Manipulation

A digital version of the Canadian Topographic Map series (NTS from Natural Resources Canada) of the Sunshine Coast and Squamish region was acquired. After identifying the relevant areas on a hardcopy in the SFU map library, the librarian (thank you Walter) forwarded the digital data in an ArcView shapefile format. There were five separate topographic maps necessary to cover the required area for this project. These were: NTS # 092G05, 092G06, 092G11, 092G12, 092G14.

In addition, in order to locate provincial parks, a shapefile was obtained from the Ministry of Sustainable Resource Management's website . The area of interest was clipped and exported to IDRISI as a vector file for analysis.

Amongst the numerous layers available on each topographic map only the layers relevant to this project were identified and imported into ArcMap from each map (buildings, built-up areas, creeks, public parks, waterbodies, and contours). It was a simple matter to open the layers up in ArcMap to look at the data, and then merge the data layer-by-layer in order to build one complete map for each layer required for my analysis. Each resulting merged layer was then dissolved separately in order to create a data set in which all the features had the same value for a specific attribute. The compiled data was then imported into IDRISI as vector files.

However, the contour layers proved to be problematic. When importing one of the contour layers into IDRISI and then converting it to a raster file I discovered that the contour measurements were not maintained, instead the contours were identified by the ID number. This was useless for my purposes.

Several methods of data manipulation were attempted. First the contour layers were merged within ArcMap, but I was unable to dissolve the resulting layer as it was too big. Using the 3D analyst I converted the new contour layer into a TIN (triangular irregular network) format, then converted the TIN to a raster format. The data did not look correct, there seemed to be a distinct difference between the boundaries of each map, they did not appear to have merged correctly. After consultation with Jasper (SFU's resident SIS expert) I decided to try creating a TIN and then converting this to a raster for each individual map before merging them together using ArcInfo's GRID module. Again the result was a map with distinct differences at the boundary of each individual map. After zooming into the boundary areas it was found that the contours were not only not meeting up in some places but were of vastly different measurements. With the help of my TA (thank you Rob Feidler) we speculated that some of the maps were in meters and some in feet! Click here for more details related to problems with the contour layers.