Faulty altitude reading

[Robin2]

When at sea level, I noticed the altitude reading in GPS status showed about 194 feet above sea level. My home address is about 60 feet asl, and shows 250 ft. Anyone else seen this? Is there a fix?
Robin

[Dave]

Altitude really isn't that accurate and can be anything from 50ft or above off. This really is what WAAS was originally designed for (e.g. flying planes) and can help better. WAAS has come on since then and is much more useful for other types of Navigation, but do expect altitude to be off, it won't be 100% accurate or anywhere close.

[Robin2]

Thanks for your reply Dave - I must remember not to use it in a light aircraft! But seriously, if it is so inaccurate, it's surely not worthwhile CoPilot displaying it
Robin

[Darren]

GPS altitude calculations are calculated using a theoretical ellipsoidal 'basemap' model of the earth. Because there is no way that geodetic altituide data for every location could be stored in a receiver.

As a result the altitude data is at best a very rough guide to height above sea level and should never be relied on. Some handheld GPS receivers encompass a barometric altitude readout which is more accurate.
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