iPhone: GPS on custom map + CATiledLayer

Really hope someone can help me as I'm a bit stuck :S

I have a custom map of an event using the CATiledLayer so users can zoom in and scroll around the map. What I would like to do now is add the functionality to let the user know where they currently are on the map. I know it can be done as I've seen an app do this before. I'm not sure how to go about doing it though, maybe I need to convert lat/lon into pixels but I'm not sure if thats possible (depending on how big the image is, etc).

On another site it was mentioned to 开发者_开发百科find out the boundaries of the map and then I can add pins to the map, but I'm not sure how to go about doing this? Will I need to find every coordinate (lat/lon) within the boundary so I can add the pin of where the user is currently?

If anyone can give me with any advice or pointers, I'd much appreciate it

You can use the route-me library by adding your own map source class. A good article that explains how to do it is here http://mobilegeo.wordpress.com/2010/07/07/route-me-native-iphone-mapping-framework/

I'm facing a challenge right now in trying to map GPS coords to a map that's an artist's rendition. In particular this is for a ski mountain, so the artist's rendition is a "trail map". The trail map is not accurate in that the whole mountain has been squeezed onto the one view, yet the actual topology of the mountain doesn't conform to the drawing.

I've tried several approaches:

1) Triangulation using known GPS coordinates of the lift stations. This is fairly simple to implement, yet this is not accurate enough and the algorithm fails if the rendition differs enough from the GPS map.

2) Creating a uniform grid for both the GPS map and the Trailmap, then doing a mapping from cells in the GPS map to the Trailmap. The downside to this is it can be a lot of busy work with no easy UI for doing it.

3) Calculating the vectors of each lift (being a straight line), find the closet lift station to a given GPS point, and calculate the estimated Trailmap location using this vector.

I'm considering #2, which is essentially the simplest solution. But if you've found a better way, I'd love to hear it.