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 Post subject: Geoid Undulation
PostPosted: Fri Aug 17, 2012 3:57 am 
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Joined: Mon Feb 22, 2010 2:35 pm
Posts: 83
Location: Honduras, Central America (FIR MHTG)
So here is a quick question in regards to Geoid Undulation, currently you need to calculate it using EGM96 but I have read discussions that EGM2008 is more accurate and that ICAO needs to change the requirement

e.g.
geoid heights (m)
EGM2008 = 5.3750
EGM96 = 5.1717
EGM84 = 4.1055

any suggestions what to do? How determining may the difference be?

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Civ. Eng. Antonio Locandro
AIM COCESNA GIS Specialist
http://www.cocesna.org/ais.php
email: antonio.locandro@cocesna.org
Tegucigalpa, Honduras (FIR MHTG)


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 Post subject: Re: Geoid Undulation
PostPosted: Fri Aug 17, 2012 2:00 pm 
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Joined: Fri Feb 26, 2010 9:31 am
Posts: 5
Within the draft document on data origination at Eurocontrol it is recommended to use EGM96, but it is also stated, that in case that higher accuracies are needed, then the EGM2008 can be applied. But as said, it's just a draft version. ICAO Annex 15 requires (shall) to use EGM96. The difference between EGM96 and EGM2008 is in the range of some decimetres.

What is worrying is the fact, that ARINC 743 describes that a geoid model has to be used within a GNSS sensor and makes a reference to NATO STANAG 4294. The later document describes a geoid model based on an article dated 1973. Therefore I assume, that GNSS sensors may use in some cases a different geoid model than EGM96.

So, if you need an accuracy in the meter or sub meter range, then EGM96 is ok. Higher accuracies can be achieved with EGM2008. But bare in mind, that if an airplane derives an altitude from a GNSS sensor, then there might be some smaller discrepancies to your altitudes. Or more generally, if you compare altitudes with different geoid references, then you have to expect the mentioned differences.


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 Post subject: Re: Geoid Undulation
PostPosted: Fri Aug 17, 2012 2:30 pm 
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Joined: Mon Feb 22, 2010 2:35 pm
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Location: Honduras, Central America (FIR MHTG)
Thank you for the answer!

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Civ. Eng. Antonio Locandro
AIM COCESNA GIS Specialist
http://www.cocesna.org/ais.php
email: antonio.locandro@cocesna.org
Tegucigalpa, Honduras (FIR MHTG)


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