In the object properties panel, with the camera selected, you'll see a little padlock in front of the height value, click it to switch it off, then your camera won't move anymore.
This parameter was introduced in Vue7 so the camera is always at the set value compared to the highest object in the scene. So if you only have a ground plane, the camera is at 1.8m above ground. If you load a sphere, the camera will be 1.8m higher than the sphere, but 7.8m higher than the ground.