The most common difference between a "performance" laptop and a "gaming" laptop would maybe be the dedicated graphics card. Some performance laptops have one and some don't, but most gaming laptops will. This makes a large difference in rendering due to not having to steal memory or CPU cycles from the motherboard. While popular with gaming, any video intensive application would benefit from this. Your description of the topographical maps sounds like it would benefit from a dedicated GPU.
Another possible difference is the monitor size. A performance laptop doesn't necessarily need to go above the 15" models. However, for gaming, a 17" can be a big draw...at the cost of lugging around a heavier machine and usually less battery life. If, however, your mobility is from one desk to another, the full size keyboard and larger screen add up to productivity increases even in non-gaming applications. Personal concerns and usage patterns, then, have a lot to do with that choice. A good docking station at home can allow you to have a large monitor and regular kb/mouse for gaming with mobility if you will be using the laptop from your car instead of a remote office.