Altitude and HAE

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Balazs Hober
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Altitude and HAE

Postby Balazs Hober » Fri May 29, 2015 12:20 pm

Question:
I am writing to you this email because I have not been activated on your forum of your website even though I become a member. I hope I can get any reply from you.

We are using DigiTerra Explorer Professional 7.14.12.19. My question is about Altitude and Height Above Ellipsoid fields. For Altitude the help menu says “Field value will be the height of the geometry = Mean Sea Level (MSL) if a geoid separation value is specified. On the other hand, again accoding to the help menu, HAE is the height above WGS84 (assuming data coming from GPS). It has been calculated using MSL and Geoid Undulation in NMEA GGA sentences, h= H (MSL)+N(geoid undulation).

Here is the question. For my project I am defining two fields: Altitude and HAE with no geoid file (so geoid undulation is always zero.) and antenna height (or upward offset) that is zero also.
When I get height using GNSS Survey (3 or 5 epochs), those two fields altitude and HAE must be equal but they are not. Sometimes there are 10 cm differences sometimes 70 cm sometimes. When I changed epoch time to 1 seconds, they are equal.

Would you please let me know how DigiTerra Explorer calculates those two fields, particularly for the case of epochs more than 1 second? Also let me know what I am missing?

Please let me know if you need further information about the question.

Thank you,
Best sincerely,

Eray SEVGEN [Mr.] | Geomatics Engineer, M.Sc.


Reply:
The difference between "Altitude" and "Height Above Ellipsoid" is the following:

Image

Altitude: this is the Z coordinate in the local projection system you are using after the received WGS84 LAT, LON, HAE position has been transformed into the local spatial reference system.

HAE (Height Above Ellipsoid):
this is the received Height value above the WGS84 ellipsoid (without transformation)

:idea: Comment: You cannot change the epoch time on the GNSS Surveying panel, this is a misunderstanding. It is planned however to be able to average positions by time also. We are currently averaging by the number of received positions with the Mean option - if you are thinking on this.

More information about the GNSS Surveying panel available at: https://digiterraexplorer.com/downloads ... survey.htm
Image

If any further question arises please do not hesitate to let me know. We are always here to help!

Best regards,
Balazs
Senior Product Manager

eraysevgen
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Re: Altitude and HAE

Postby eraysevgen » Fri May 29, 2015 1:02 pm

Altitude: this is the Z coordinate in the local projection system you are using after the received WGS84 LAT, LON, HAE position has been transformed into the local spatial reference system.

It does not make sense. You mean orthometric height or mean sea level using the term of Z. In local projection it is not defined as Z, it is height, but this time it is capital, H. Z term is being used for geocentric coordinates, like ITRF. Vertical component of local spatial system is handled differently. There are two different height, Ortometric and Ellipsoidal.

I am working in WGS 84 UTM Zone 37 N (this is my local projection), without geoid undulation. So my height is still in HAE. But I have two different heights for "Altittude" and "HAE". Th's is the problem. I think the problem is clearer right now.I am waiting your reply.

HAE: It is the height coming from GGA.

Average: Thank you for this.

Thank you.

Eray

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Balazs Hober
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Re: Altitude and HAE

Postby Balazs Hober » Fri May 29, 2015 2:38 pm

Dear Eray,

Let me correct it. "Altitude" always means Orthometric height in DigiTerra Explorer. When you are using a Geoid undulation model the Altitude is "height above sea level". In geoinformatics "x" is the East, "y" is the North and "z" is the height. You are correct that the CAPITAL "Z" term used to mark the "Z" axis of the geocentric coordinate system.

If you are using WGS 84 / UTM zone 37N WITHOUT geoid model the ellipsoid height (Height Above Ellipsoid) and orthometric height (Altitude) should provide the same value.

One more question: are you using external antenna at Settings > Antenna tab like this below?
Image

To investigate this issue for you please send me over the project in a .ZIP file and also log an NMEA logfile at your current location, that you can make by opening the Settings panel > Logger and using the following settings as below:

Image

Waiting for your reply.

Thanks,
Balazs

eraysevgen
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Joined: Tue May 26, 2015 7:57 am

Re: Altitude and HAE

Postby eraysevgen » Fri May 29, 2015 3:49 pm

Dear Balazs,

I am happy to see that you got the point about the problem I was trying to explain. I am going to provide what data you have requested next week.

I am aware of antenna height and it is always zero in this case.

Thank you very much.

Eray

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Balazs Hober
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Re: Altitude and HAE

Postby Balazs Hober » Fri May 29, 2015 11:45 pm

Dear Eray,

I am looking forward to your reply on the next week with the requested data to investigate this issue for you. It is okay to send it in email to this address: support@digiterra.hu, but you can also attach them here in the forum. We'll be attempting to do our best to resolve your issue in the most timely and professional manner we can!

Thanks & best regards,
Balazs

eraysevgen
Posts: 7
Joined: Tue May 26, 2015 7:57 am

Re: Altitude and HAE

Postby eraysevgen » Mon Jun 01, 2015 2:30 pm

Dear Balazs,
I have sent the email to support@digiterra.hu.

Thank you in advance.
Best regards,
Eray

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Balazs Hober
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Re: Altitude and HAE

Postby Balazs Hober » Wed Jun 03, 2015 3:51 pm

Dear Eray,

We have found and fixed what caused this issue to you. Please have a look at this link: http://www.screencast.com/t/EHn2Ek99
The HotFix can be downloaded at http://goo.gl/Y2IIUo

Please follow these instructions at https://digiterraexplorer.com/downloads ... mobile.htm regarding installation of this HotFix.

Apologize for the issue that this bug caused to you. If you need any further help please let me know.

Thanks,
Balazs

eraysevgen
Posts: 7
Joined: Tue May 26, 2015 7:57 am

Re: Altitude and HAE

Postby eraysevgen » Thu Jun 04, 2015 1:13 pm

Dear Balazs,

Thank you for a quick reply. I did not expecting you to fix this issue this fast.

We are using DigiterraExpolorer on Panasonic FZ-G1 Toughbooks with Windows 7 64 bits OS. So, our Digiterro Explorer is Desktop version. Am I going to download the desktop version of the update not the mobile version ? Then I am going to follow the instructions for desktop version.

Thank you again.
Best regards,
Eray

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Balazs Hober
Site Admin
Posts: 260
Joined: Fri Aug 08, 2008 12:53 am
Location: Hungary, Budapest
Contact:

Re: Altitude and HAE

Postby Balazs Hober » Thu Jun 04, 2015 2:51 pm

Dear Eray,

Thank you for your response. We are committed to help you on time. In your case the update process is much easier for the Desktop:

1. Open this link in your browser: http://goo.gl/Y2IIUo
2. Click "Desktop"
3. Then click "DTEXPV7DesktopSetup.exe" to download as you can see it on this screenshot below:

Image

4. Finally double click on the downloaded "DTEXPV7DesktopSetup.exe" and follow the instructions of the installer. It will automatically update your software and install this HotFix.

I am always happy to help, so please do not hesitate to contact me again if any further question arises.

Thanks,
Balazs

eraysevgen
Posts: 7
Joined: Tue May 26, 2015 7:57 am

Re: Altitude and HAE

Postby eraysevgen » Thu Jun 04, 2015 3:13 pm

Dear Balazs,

It is still same. Nothing changed after update. I mean altitude and HAE still not equal. I have resent an email to support@digiterra.hu.

May I missing something?

Thank you.
Best regards,

Eray


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