[gdal-dev] Request for clarification on SPARSE_OK=TRUE and empty tiles relation

[Daniele Romagnoli]

Hi list,
I have seen a recent email on that list about filling empty tiles and
SPARSE_OK creation option (titled "Geotiff FillEmptyTiles with no data
value")
I would like to understand a little better how it works.

Suppose I have 2 isolated GeoTiff files of the same datatype, let's say one
covering California and the other covering France.
I do a gdalbuildvrt to mosaic them together and then I convert the VRT to
GeoTiff.
At which level the SPARSE_OK flag and void blocks management are taken into
account?
I was "hoping" that using the SPARSE_OK=TRUE create option when translating
VRT to GeoTiff would have resulted into having an output smaller with
respect to an output generated without that creation option since there is
a wide void area in the middle.
Why I get the same size in both cases? Shouldn't it avoid filling void
blocks in the gap?
Is the VRT Driver iterating on all the tiles involved in the final bounding
box so that it forces a write of each block even if there is no source
dataset for that tile?

Please, let me know.
Best Regards,
Daniele


-- 
==
GeoServer Professional Services from the experts! Visit
http://goo.gl/it488V for more information.
==

Ing. Daniele Romagnoli
Senior Software Engineer

GeoSolutions S.A.S.
Via di Montramito 3/A
55054  Massarosa (LU)
Italy
phone: +39 0584 962313
fax:      +39 0584 1660272

http://www.geo-solutions.it
http://twitter.com/geosolutions_it

-------------------------------------------------------

*AVVERTENZE AI SENSI DEL D.Lgs. 196/2003*

Le informazioni contenute in questo messaggio di posta elettronica e/o
nel/i file/s allegato/i sono da considerarsi strettamente riservate. Il
loro utilizzo è consentito esclusivamente al destinatario del messaggio,
per le finalità indicate nel messaggio stesso. Qualora riceviate questo
messaggio senza esserne il destinatario, Vi preghiamo cortesemente di
darcene notizia via e-mail e di procedere alla distruzione del messaggio
stesso, cancellandolo dal Vostro sistema. Conservare il messaggio stesso,
divulgarlo anche in parte, distribuirlo ad altri soggetti, copiarlo, od
utilizzarlo per finalità diverse, costituisce comportamento contrario ai
principi dettati dal D.Lgs. 196/2003.



The information in this message and/or attachments, is intended solely for
the attention and use of the named addressee(s) and may be confidential or
proprietary in nature or covered by the provisions of privacy act
(Legislative Decree June, 30 2003, no.196 - Italy's New Data Protection
Code).Any use not in accord with its purpose, any disclosure, reproduction,
copying, distribution, or either dissemination, either whole or partial, is
strictly forbidden except previous formal approval of the named
addressee(s). If you are not the intended recipient, please contact
immediately the sender by telephone, fax or e-mail and delete the
information in this message that has been received in error. The sender
does not give any warranty or accept liability as the content, accuracy or
completeness of sent messages and accepts no responsibility  for changes
made after they were sent or for other risks which arise as a result of
e-mail transmission, viruses, etc.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/gdal-dev/attachments/20160516/2a3c769f/attachment.html>