Negative altitudes are incorrect on the height indicator

[fbonzon]

Steps

• Enable height indicator option
• Render an elevation profile where some or all altitudes are below 0. E.g. near the Dead Sea

Actual

When mousing over negative altitudes on profile, height indicator has incorrect size. It is much longer than expected. This is because the normalized altitude formula assumes lowest is 0.

Expected

The height indicator has size normalized to the range "lowest altitude to highest altitude".