Ensuring Projections are all Matched

One of the major problems with all the different data sets that we obtained from our various sources was that the projections were either undefined or in different projection systems. Therefore, it was very important for all projections systems to be defined in order to view all the shape files simultaneously.

For the first data set we were told that is was projected in BC Albers 83, the coordinates were present but the projection was not defined. In order to define the projection we imported BC Albers 83 from the BC_lakes map from the GIC’s data base. We used arcToolbox, under data management tool>projections>define projection wizards (shape file) and found the BC_lakes map from the imported files. Once one shape file was assigned this coordinate system we imported the coordinate system from the first altered shape file to all other shape files to ensure that all coordinate systems matched.

The second and third data sets were also undefined. All the data had coordinates in decimal degrees and therefore we defined the projection to NAD 83 for it to be projected the same as the first data set within arcGIS. Again, arcToolbox under data management tool>projections>define projection wizards (shape file), was used to define the projection. NAD 83 projection was found from the provided selection under geographic coordinate systems>NorthAmerica>NAD 83. Once one shape file was assigned this coordinate system, we imported the coordinate system from the first altered shape file to all other shape files to ensure that all coordinate systems matched.

The last data set that was provided to us had an undefined projection system and the coordinate system matched that of NAD 83, therefore the two shape files that were of use to us were defined by importing the NAD 83 from the second data set following the same method as above.

Clipping Hornby Maps from BC Maps

Before starting the analysis of the data there was still additional preparations needed. Some of the data sets that were provided were for the whole BC coast. Since we were only interested in Hornby Island we went through and clipped Hornby Island from all the shape files. This was performed by doing a selection by location process. One of the shape files was just of Hornby Island and therefore we used it as a base map. For each data set that extende beyond Hornby, we selected by location the shape files we wanted to clip to and selected everything that intersects with the shape file of just Hornby Island. Then after each selection we exported the data and saved it to a desired file to ensure that the selection that was created was exported into its own layer.

For example, we selected by location the dempts.shp of Hornby Island that intersected with geology.shp and then exported the selected data to create a separate layer. This provided us with a data set that just included Hornby Island. It is these shape files of Hornby that were used for data manipulation.

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