Matronics Email Lists :: View topic - Appeal to European Europa owners, aviation Garmin question

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Appeal to European Europa owners, aviation Garmin question

Matronics Email Lists Forum Index -> Europa-List

View previous topic :: View next topic

Author Message

Richard Lamprey

Joined: 15 Jul 2011
Posts: 95
Location: Kenya

Posted: Mon Aug 27, 2018 10:44 pm Post subject: Appeal to European Europa owners, aviation Garmin question

Dear all,

An appeal from a fellow Europa owner, Europa Classic Mono 5Y-LRY in Kenya, East Africa.



I would be truly grateful to anyone in UK with an aviation Garmin, especially Garmin 96, 196, 295/6, 396 or 495/6 who can help me.  Do you live by the sea?  Can you walk on your beach (when convenient!), turn on your GPS, let it settle, and tell me what altitude/ elevation above / below mean sea level (MSL) that your unit reads?  It would be best if, beforehand, you can set the coordinates to latitude/ longitude, datum to WGS84, turn off WAAS or EGNOS augmentation



Generally speaking, GPS units measure altitude as a distance to the 'reference ellipsoid' of WGS84, this being the squashed-ball representation of the earth.  But much research has shown that the gravity of the earth is lumpy, and that MSL is therefore lumpy.  This lumpiness is incorporated into the 'earth geopotential model' ('geoid') EGM96 (now updated to EGM2008), generated by NASA from satellites measuring gravity. Some GPS units also incorporate EGM96 into their altitude corrections, but, despite my constant queries to them, Garmin has been absolutely tight-lipped about whether they do this for their aviation units, and there is no reliable information online.



The 'height' difference between EGM96 and the reference ellipsoid WGS84 is highest in northern Europe (something like 70m), hence my question to UK Garmin owners (or in France or Scandinavia)!  In East Africa this difference is just 15m.  



Please note this is not a question about the general precision / accuracy of elevation measurements using GPS units, which is much researched, but about geoid offsets that might be hardwired in to GPS units.



This information is vital for our research into use of GPS elevation logs in aerial wildlife surveys in Africa (my field of work).



So... earth physics lecture over, just need your altitude above/ below MSL!!

Thanks, your help very much appreciated!  



Richard,

Europa Classic 5Y-LRY, Mono, 912UL, Kenya

- The Matronics Europa-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?Europa-List

Ivor

Joined: 23 Jul 2015
Posts: 51

Posted: Sat Sep 01, 2018 11:03 am Post subject: Re: Appeal to European Europa owners, aviation Garmin questi

hi Ritchard not sure if this is relevant to your question but on Friday at 

Lydd EGMD that is 10 feet above sea level my Garmin 496 was showing a    GPS altitude of 25 feet

- The Matronics Europa-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?Europa-List

Richard Lamprey

Joined: 15 Jul 2011
Posts: 95
Location: Kenya

Posted: Mon Sep 03, 2018 1:41 am Post subject: Re: Appeal to European Europa owners, aviation Garmin questi

Ivor, thanks very much, this is very useful and relevant!  If you have a chance, could you just confirm in your Units page, if your map datum is WGS84 (or the datum it is set to)?  And in System Setup, also that WAAS and EGNOS are turned off?



After 6 months of prodding to Garmin UK Technical Department, still no clear answer on geoids, but will keep trying!

Thanks again

Best

Richard

- The Matronics Europa-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?Europa-List

Ivor

Joined: 23 Jul 2015
Posts: 51

Posted: Mon Sep 03, 2018 2:13 am Post subject: Re: Appeal to European Europa owners, aviation Garmin questi

Ritchard  

i am not going to the airfield for a couple of weeks but will try and check for the information you require next time i do,



regards

Ivor

- The Matronics Europa-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?Europa-List

Richard Lamprey

Joined: 15 Jul 2011
Posts: 95
Location: Kenya

Posted: Tue Sep 04, 2018 11:49 pm Post subject: Re: Appeal to European Europa owners, aviation Garmin questi

Thanks Ivor, much appreciated!  Best

Richard

- The Matronics Europa-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?Europa-List

Display posts from previous:

	Matronics Email Lists Forum Index -> Europa-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum