Why does the altitude differ between my sailplanes altimeter and what Soaring Pilot shows and which one is correct?
Basically, the barometric pressure in the atmosphere does not decrease evently as you climb. In addition, barometric pressure is not constant for given altitude eveywhere. Given this, it is not uncommon for an altimeter to read around 200 feet lower than GPS altitude when flying at around 3000-4000 feet AGL. So, that means that technically GPS altitude is more accurate. However, as with the accuracy question above, there have been numerous discussions on this subject on the rec.aviation.soaring and sci.geo.satellite-nav newsgroups. In addition, GPS altitude is an MSL calculation. It has been said that the Height Above the Ellipsoid (HAE) will provide a value closer to pressure altitude. MSL is the default altitude reference but can be changed to HAE on the Final Glide settings page.
Related Questions
- To record altitude data, can we use another brand of altimeter that has the same performance specifications as the Adept A1-TA?
- Why does the altitude differ between my sailplanes altimeter and what Soaring Pilot shows and which one is correct?
- How can you determine pressure altitude without setting the altimeter?
