R: [Users] Trace Re-sampling in OpendTect

[Arnaud Huck]

Dear Antonio,
Thanks for your feedback. See below my comments.

Best regards,
Arnaud.

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Corrao Antonio wrote:
> Arnaud,
> I am interested in using the re-sampling feature, especially in some plugins I am working on.
> But before moving to developed code, I did check what you suggested.
> Actually copy cube and export do support user supplied sampling rates, but create seismic output does not: you can specify ranges X/Y/Z but sampling is fixed.
>   
You are right. I did not check this third option.
> I am not surprised by that, as when I asked Nanne about oversampling he said it was not possible (March 19, during SSIS II meeting).
> I checked version 3.0.1c as well as 2.4.2 and they both do not allow that.
>   
Oversampling might not work when creating an output you are right too, 
but it works by decimation when using the copy cube option. So you can 
always go back to your newly created cube and decimate it, or you might 
want to decimate your input cube prior to computing an output with it.

> AC
>
> Antonio Corrao
> Senior Geophysicist
> GEOS dept. - Eni E&P Division
> V. Emilia 1 - 20097 San Donato Milanese - Italy
> Tel:+39.02.520.61150 - Fax:+39.02.520.63897 - mailto:antonio.corrao at eni.it
> _____________________________________________________________________________
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>   
>> -----Messaggio originale-----
>> Da: users-bounces at opendtect.org@ENIEXT at ENI Per conto di Arnaud Huck
>> <arnaud.huck at dgb-group.com>
>> Inviato: martedì 29 maggio 2007 13.32
>> A: dGB OpendTect userlist
>> Oggetto: [Users] Trace Re-sampling in OpendTect
>>
>> Dear OpendTect users,
>> You might not know it because there is no special button for it, but
>> OpendTect can re-sample your (seismic and attribute) traces.
>>
>> Already for computations along picksets and surfaces, re-sampling is
>> necessary. Indeed, picksets and surfaces are not snapped to the nearest
>> sample. As a result, when applying an attribute to those locations, the
>> traces are re-sampled on the fly to get under-sampling accuracy.
>>
>> Now, it is possible to store a re-sampled volume.
>> For over-sampling or under-sampling,  i.e. in order to modify the
>> sampling rate of your volume, you have to use the "copy cube" option,
>> available from the seismic manager. By using the default "Volume
>> subselection", which is set to "none", the sampling rate will not be
>> modified. If you press the "Select button", and mark the "Sub-volume"
>> option, the new sampling rate will be defined as the one specified in
>> your survey settings. By modifying the step value, you will re-sample
>> your volume (if the specified step is different from the original).
>> Please note that over-sampling will be done by decimation.
>>
>> In general, there are many places in the software where you have this
>> "Subselection" option; Import - Export - copy cube - create output. All
>> of them will behave like I explained above.
>>
>> In order to apply shifts that are below the sampling rate (general
>> situation), please use the reference shift or delta-resample (3.0 and
>> later only) attributes. Reference shift is for applying a constant shift
>> to whole volume, while the new attribute delta-resample will use
>> variable shifts originating from a stored volume or an attribute.
>>
>> A third order polynomial interpolation is used for the re-sampling.
>>
>> Best regards,
>> Arnaud.
>>
>> -- dGB Earth Sciences B.V.
>> -- Nijverheidstraat 11-2, 7511 JM Enschede, The Netherlands
>> -- mailto: arnaud.huck at dgb-group.com, http://www.dgb-group.com
>> -- Tel: +31 53 4315155 , Fax: +31 53 4315104
>>
>>
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