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Study Design
Background Research
Data Acquisition
Data Preparation and Manipulation
Methodological and Operational Errors
Conclusion
References

    A multi-criteria evaluation was conducted in order to find the most suitable areas of the GVRD for the creation of a new skate park. The spatial analysis for this geographic information science project was conducted in the IDRISI software program. To view the cartographic model for the multi-criteria evaluation click here.
   
    In order to start the multi-criteria evaluation, I needed to decide which images would become constraints and factors. The image of parks in the GVRD was chosen to be a constraint image, because it does not make sense to rescale an already boolean image and there is no need to take into account the surrounding areas as only land in parks will be considered for a new skate park. The final analysis can only be in park areas, so it makes sense to make it a constraint which will "mask out" the final data in the multi-criteria evaluation. The transit image (bus stops and SkyTrain) was chosen to be a constraint image, because attempts to run the transit image as a fuzzy factor failed to come up with a reliable final image. It is postulated that the distances from the transit were too large in the fuzzy set membership for the whole image extent and ultimately confused the multi-criteria evaluation. The railway image was chosen to be a constraint image, because for the same reasons listed for the transit image. The two images on the population density of males at various ages was chosen as a factor variable, because high density is important, but if all the other constraints are true then a medium density is acceptable.

    All the data was obtained in vector format and needed to be transformed into raster so the Idrisi software program could use it in the multi-criteria evaluation. After this conversion happened it was possible to adjust the images so that they would work in the multi-criteria evaluation. In order to have the park, transit, and railway images work in the multi-criteria evaluation they first needed to be transformed into boolean images. An image containing only parks needed to be extracted from the GVRD land use image. This was done by using the module assign to create a boolean image. To view the parks image click here. An image containing the transit bus stops and SkyTrain had the buffer module applied to it in order to create a 528 meter area around and containing transit routes. A 352 meter buffer was used, because it was assumed that teens would only be willing to walk for approximately three blocks to the nearest transit pick up location. To view this image click here. An image containing the railways had a buffer applied to it so that the railway and 255 meters area surrounding the railway were excluded while everything else was included. A 255 meter buffer was used, because it was assumed that a buffer of between one and two blocks was enough for the safety of the skate park users. To view this image click here.
   In the process of doing the multi-criteria evaluation the two population density of males images were turned into fuzzy images, meaning they were rescaled from the original 0 to 120 to 0 to 255. The fuzzy images were created using a monotonically increasing J-shaped membership function, because the function drops from high suitability very steeply. This suited the data, because only high density of males was wanted in the final multi-criteria evaluation. The control points were selected as: a=0 and b=180, because the range of values in the data was 0 to 120 meaning only the top 10% of the density of males in the GVRD lies between b and d. To view the fuzzy images of the two population density of males images click here.

    Once all the input images to the multi-criteria evaluation was completed it was then necessary to specify the relative weight of the factors used. In this case the only two factors that were used were both population density factors, so they had equal weight. Once the equal weighing was specified the multi-criteria evaluation module ran in Idrisi to produce a final image of the most suitable locations for a new skate park in the GVRD. To view this image fast forward to the Conclusion.

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