difference in elevation; altitude difference
Used for vertical distance between two points, often in geography, construction, or sports contexts.
This course has a steep elevation change.
Measure the difference in elevation between the two points.
高低差 specifically means a difference in elevation between two points, while 落差 more often describes the drop of falling water like a waterfall.
Compound of 高低 (high and low) and 差 (difference).