One of my best life decisions was trekking in Patagonia for six weeks in my early twenties. I went alone, armed with the Lonely Planet Guide to Patagonia and an enormous backpack. I expected to pick up some backpacking necessities in local shops, and indeed I found everything I needed except a map.
|Lago Nordenskjold, I believe|
Yes, there were maps, but none with the detail I was hoping for. Most I found looked like a US national parks map - it shows the trail and information about the area, but not much in the way of topography. This is true for many international destinations - the United States Geographic Service does an exceptional job producing (expensive to make) topographic maps of the US, and some governments don't want to widely distribute sensitive geographic information to protect national security.
Hillmap.com has two different map layers that cover many international locations, including Patagonia and Torres del Paine. They are not as detailed as the US or Canada map layers, but they display more topographic information than the maps I found at local shops. It has been a few years, so there may be better maps available now (and if you've been and found great maps, please share in the comments so others will know!)
Here are snapshots of the map layers
Google Terrain and Satellite
I did not take a gps with me, but you can find gpx trax for the Torres del Paine Circuit on the Without Baggage blog, and import the gpx track to hillmap to explore the terrain further on both map layers.
Print a few maps at home for free, and bring them on your trip.
|Los Torres at dawn|
Torres del Paine was one of the parks I visited, and I was ok without a detailed topo map since I stuck to the well worn trail. All visitors must camp or stay at the hostels along the route, camping where you want is not allowed. It is possible to get a permit for climbing and other adventures that take you off the main track.
If I return I will certainly explore beyond the trail.....