elevation vs altitude

Temperature is measured with a sensor on a pole, perhaps two metres above the ground, which is not a particularly significant amount at 2000m above sea level. You could just as well call the height of the sensor 2000m above sea level, treating the height of the ground and the sensor fixed to the ground as more-or-less coincident.

Elevation is usually used to describe the height of the ground, or a feature fixed to the ground.

Use elevation.