Bottlang Height reference: which geoid model?
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Bottlang Height reference: which geoid model?
My question is:
As we all know, in the Jeppesen Bottlang Airfield Manual, the airfield elevation (elevation of ARP) is stated. I assume that this is above MSL, or, technically speaking, above the "geoid".
However, "GPS height" refers to the WGS-84 reference system, with heights given as meters above the spheroid (or "ellipsoid"). To convert one elevation into another, I need to know the difference between the geoid height and the spheroid height. There are software programs available that allow me to do this.
However, for this I need to know the geoid model used by Jeppesen (there are hundreds of models that can be used).
So,
Which geoid model is used by Jeppesen for the calculation of MSL height?
Thankyou for your comments,
SF
As we all know, in the Jeppesen Bottlang Airfield Manual, the airfield elevation (elevation of ARP) is stated. I assume that this is above MSL, or, technically speaking, above the "geoid".
However, "GPS height" refers to the WGS-84 reference system, with heights given as meters above the spheroid (or "ellipsoid"). To convert one elevation into another, I need to know the difference between the geoid height and the spheroid height. There are software programs available that allow me to do this.
However, for this I need to know the geoid model used by Jeppesen (there are hundreds of models that can be used).
So,
Which geoid model is used by Jeppesen for the calculation of MSL height?
Thankyou for your comments,
SF
Join Date: Nov 2002
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I am quite sure Jeppesen/Bottlang does not do any calculation regarding airfield elevation. Normally (always?) they re-publish data off the National AIP which defines which height datum is used. Normally this will be the nationally defined MSL.
As GPS is not (yet?) in use for height measurements in aviation, the issue is not operationally relevant.
If you want this confirmed, why not ask Jeppesen? You can access their homepage on www.jeppesen.com.
Is this satisfactory?
LIN
As GPS is not (yet?) in use for height measurements in aviation, the issue is not operationally relevant.
If you want this confirmed, why not ask Jeppesen? You can access their homepage on www.jeppesen.com.
Is this satisfactory?
LIN
Join Date: Mar 2000
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With the GPS fitted to most aircraft--
Oddly enough, GPS indicated height (with the local station pressure inserted) above MSL, is within 50 feet of the pressure altimeter, at altitudes below 17,500 in the USA where QNH is used.
QNE would be a different case altogether.
Oddly enough, GPS indicated height (with the local station pressure inserted) above MSL, is within 50 feet of the pressure altimeter, at altitudes below 17,500 in the USA where QNH is used.
QNE would be a different case altogether.
You'd have to be lucky to get it within 50 ft at higher levels. The barometric altimeter is subject to a temperature error of about 0.35% (of height above datum) per degree Celsius deviation from ISA. At 15,000 ft, that's 50 ft per deg C. I've not seen a GPS with a temeparture input as well as QNH/altimeter-setting.
