Choosing between projection systems

Question

I'm a Python/Django developer who is new to GeoDjango (and GIS, in general). I was hoping someone could provide some guidance with respect to the different projection systems offered by the City of Toronto.

The City of Toronto is great with publishing Open Data. Here's a link to their Open Data repository.

All shapefiles are available in both "MTM 3 Degree Zone 10, NAD27" as well as "WGS84" formats. GeoDjango is able to import both formats. What are the consequences of choosing to import data from one format as opposed to another? What factors should I consider when deciding?

Answer 1

Depends on how you are using the data. If you are layering it on top of other datasets, choose a common coordinate system for all datasets so that your mapping framework doesn't have to reproject the data every time a map is drawn. WGS84 is a very popular coordinate system, and would be a good choice for mixing with other data.

If you are just using it to generate maps in the Toronto area, MTM 3 Degree Zone 10 is probably your best bet, as WGS84 will introduce slight distortions when drawing a map on the screen, although casual (and probably advanced) map users will be unlikely to notice it.