It is about 2 1/2 hours travel time to get to Dorset and 250 kilometers. Dorset is just south of Algonquin Park (about 30 minutes drive).
* Take Highway 400 north towards Barrie
* Take Take provincial Route 11 North toward Orillia/North Bay
* Take the District Route(provincial route) -117, Cedar Lane exit- exit number 193- toward Baysville
A website that I like very much is this online roadmap :
In this next link I already choose the map with the area of Dorset for you (coordinates N27 on the map).
With this website you can click on a part of the map of Ontario, and get the roadmap for that area. You can zoom in very good on an area, so it makes the map easy to read. Another option is to go to the index of place-names, and search the map that way. The maps are quite large, so it might take some time to download.