In addition to the mouse wheel, use the four arrow keys.
Left/right will provide the lateral movement.
Up/down arrows will vary the vertical angle of view. Together with the mouse wheel you should be able to move some way back.
The space bar will usually take you, in very short steps, in the direction last moved using RMB+move mouse to travel over the terrain. These results apply when the compass movement in Surveyor Options is set to mouse. The behaviour is slightly different when set to keys.
You may also be able to change the -surveyorfov value for a higher number in the trainzoptions.txt file if you want a generally wider angle of view in Surveyor. I say may because I don't have TS12, but I'm guessing that all of this is still possible.