1>c:\***\thegame\terrain.cpp(13): error C2758: 'Terrain::mCamera' : must be initialized in constructor base/member initializer list
1> c:\***\thegame\terrain.h(72) : see declaration of 'Terrain::mCamera'
This tells you that you need to initialize the reference in the initializer list of the constructor.
1>c:\***\thegame\terrain.cpp(128): error C2327: 'Terrain::mCamera' : is not a type name, static, or enumerator
1>c:\***\thegame\terrain.cpp(128): error C2065: 'mCamera' : undeclared identifier
1>c:\***\thegame\terrain.cpp(128): error C2228: left of '.getPos' must have class/struct/union
1> type is ''unknown-type''
Without seeing the code here, I can't tell you exactly what's going on here, however it basically is just telling you that it has no idea what mCamera is, its not encountered it within the current name scope. The code you pasted is, pretty much, useless.