horizon export issue

[Brian Brennan]

Hello users.

Working through a horizon export issue on a Saturday afternoon. Maybe one of you is similarly obsessed and can help me out.

Here is the problem: I've converted a horizon from depth to time within OD. I have also exported the horizon. The export looks like it has the correct values but it also has a lot of what appear to be nonsense numbers. Below is a screenshot of the output file showing both. Export was in ms, so the numbers halfway down look fine. I haven't imported them yet so I'm not sure. But the numbers at the top of the window are clearly not right.

Thanks for any help you can give me. 

Now go back to enjoying your weekend.

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Brian Brennan

Geophysicist

337-258-3641

email: BrianDB...@gmail.com

website: Third Wave Geophysics.com

[Joel Scott]

 Brian,

Could be result of division by zero?

Joel Scott 

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From: Brian Brennan <briandb...@gmail.com>
Sent: Saturday, January 10, 2026 1:55:58 PM
To: us...@opendtect.org <us...@opendtect.org>
Subject: [OpendTect_Users] horizon export issue

 

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[M T]

If you go to some of these coordinates with the Z value in scientific notation at the top of the list, can you tell us what the values should be?

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[Friso Brouwer]

Those errand values are essentially zero. To understand the problem it might be worth plotting average velocity from surface to horizon, horizon in depth and horizon in time side by side. Of the origin is in the data this will reveal it, if this is not the problem you know to look elsewhere. An example of what may have gone wrong is undefined value coded in the velocity volume represented by very high numerical values being treated as real velocities and mapping the horizon back to 0ms. This has happened to me storing velocities in the 16bit format.

I hope this gets you somewhere, have a good weekend.

On Jan 10, 2026, at 15:10, Brian Brennan <briandb...@gmail.com> wrote:



Hello users.

Working through a horizon export issue on a Saturday afternoon. Maybe one of you is similarly obsessed and can help me out.

Here is the problem: I've converted a horizon from depth to time within OD. I have also exported the horizon. The export looks like it has the correct values but it also has a lot of what appear to be nonsense numbers. Below is a screenshot of the output file showing both. Export was in ms, so the numbers halfway down look fine. I haven't imported them yet so I'm not sure. But the numbers at the top of the window are clearly not right.

Thanks for any help you can give me. 

Now go back to enjoying your weekend.

<image.png>

--

Brian Brennan

Geophysicist

337-258-3641

email: BrianDB...@gmail.com

website: Third Wave Geophysics.com

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[Brian Brennan]

Thanks for the help all. 

Is there a way to specify the format of the output file? If I limit the  z field number to 2 decimal places I guess those would all be zeros. 

Or maybe I can just import it and delete all values that are ~zero. 

Sent from my iPhone

On Jan 11, 2026, at 2:29 AM, Friso Brouwer <fr...@i3geo.com> wrote:



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[Paul de Groot]

Hi Brian,

I would import the horizon AS IS and change the values in OpendTect. If you are a Pro user you can use Horizon Mathematics to replace all values close to zero to real zeros or undefined values (undef or 1e30). The formula looks like this:

(Zval < C0 && Zval > -C0)? 0 : Zval

Where Zval is the Z value of the input horizon and C0 is a constant.

If you use the community version, you can do the same in the attribute engine using the Mathematics attribute. Apply the formula to the horizon and save as horizon data. Export the horizon data and re-import as a new horizon.

Best regards,

Paul.

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Paul de Groot

Special Adviser

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Phone: +31 53 4315155 E-mail: paul.d...@dgbes.com Internet: dgbes.com

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