Thursday, October 21, 2010

Generate Map (or Stats) on Students' Transit Access Using Postal Codes


A Student Association is trying to determine how many students do not have convenient access to transit, which it defines as being more than a 15-minute walk from a transit station or bus stop. It is in negotiations with the local transit company about a proposed student transit pass. I have a couple of questions:

Would the Student Association be eligible to use DLI resources for this purpose (assuming they will be of help)? I suspect not since it is a separate organization from the university. This issue is of interest to the university’s planning office as well, however, and it has provided the Student Association with a list of the number of students living in each 6-digit postal code.

Could any of you with GIS experience suggest how to best approach this, with or without DLI resources? Unfortunately, our Library does not subscribe to DMTI Spatial’s Platinum Postal Suite (or any DMTI products), nor do we have PCensus. We do have ArcGIS installed on some workstations.

I’m afraid that I have very little experience – aside from some excellent DLI training sessions and the National Summer Institute last year – on using mapping software. I have spent a bit of time thinking about various approaches I might recommend to the Student Association with the limited resources we have available, and could probably spend all day bumbling around trying them out. I actually wouldn’t mind this, in order to get some experience using the tools, but the Student Association needs the info fairly urgently.

The transit company provides PDF route maps on its website and has also made route data available in Google Transit Feed Specification (GTSF) format. The Student Association has generated a PDF map showing its rough boundaries of ‘convenient access.’

Any help will be appreciated.


Here is how I would basically approach this request.

The first step would be to geocode the student list using their postal codes. Using the PCCF (if use allowed) you would assign each student latitude and longitude coordinates based on the postal code they live at. You would then add these students as x/y points to the map.

The second step would be to obtain a point shapefile of all the bus stops and SkyTrain stations. I had a quick look at the Google Transit Feed Specification and I think this could probably be created from one of the files if you don't have access to the actual shapefile from TransLink.

The third step would be to create buffers around each bus stop and SkyTrain station using some distance that would approximate a 15-minute walk (500-1000 meters).

The fourth step would be to select by location all the students that fall outside those buffers. This would give you the number of students without convenient access to transit.

Additional information

We consulted the DLI Executive and they confirmed that the Student Association and/or the university's planning office would be allowed to use DLI products (such as the PCCF) for this specific project. As students and staff, they are authorised users and this project can be considered academic planning and is therefore allowed according to the DLI licence. The students would of course need to be made aware of the licence and its restrictions (e.g. the DLI products can't be used by the transit company).

I hope that this is helpful. If you have any other questions, please don't hesitate to let us know.

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