Contrast topographic elevation with bathymetric depth.

Topographical elevation is a height in reference to a geometric sphere. Most maps use sea level as a reference sphere, and have topographic elevation above or below that line.

Bathymetric depth is a depth below the surface of water. This is used to make maps of the sea floor and lake beds, and can even be used in rivers.

To contrast the two, I would say that topographic height can be used anywhere, as it is applicable to any height on any surface, whereas bathymetric depth is only useful on underwater surfaces, and as such is always negative. 

The uses of these two types of numbers also vary. People will use topographic height in land navigation, and bathymetric depth while navigating the sea.