[gdal-dev] Should we make also GTiff to use TILED=YES as default?

[Rahkonen Jukka (MML)]

Hi,

On the other hand those QGIS users pay the price every time when they zoom close to the same image because then QGIS must read many super wide rows of data instead of just the tiles that intersect the view. Not even overviews which are created on top of striped image do not help when user hit the native resolution. But perhaps it is not so important what is the default, experienced users maybe know what they want.

-Jukka Rahkonen-

Lähettäjä: Javier Jimenez Shaw <j1 at jimenezshaw.com>
Lähetetty: tiistai 30. marraskuuta 2021 11.09
Vastaanottaja: Rahkonen Jukka (MML) <jukka.rahkonen at maanmittauslaitos.fi>
Kopio: gdal-dev at lists.osgeo.org
Aihe: Re: [gdal-dev] Should we make also GTiff to use TILED=YES as default?

Hi Jukka

I don't think it is a good option.
TL;DR: tiled without overviews is extremely slow for a global view.

If you have a (big) image with TILED=YES but without overviews, it is really really slow in QGIS (from seconds to many minutes).
The reason (I guess) is that QGIS is by default sub-sampling the image using nearest neighbor. If the image is not tiled, then it has to read only every nth line. However, when tiled, at the end has to read the full image from file.
The bigger the zoom level, the faster it goes. But waiting 5 minutes to see the global view of your image to know where to zoom in... you close QGIS and blame somebody.

That changes dramatically if there are (proper) overviews available, of course.

Cheers
.___ ._ ..._ .. . ._.  .___ .. __ . _. . __..  ... .... ._ .__
Entre dos pensamientos racionales
hay infinitos pensamientos irracionales.


On Tue, 30 Nov 2021 at 08:04, Rahkonen Jukka (MML) <jukka.rahkonen at maanmittauslaitos.fi<mailto:jukka.rahkonen at maanmittauslaitos.fi>> wrote:
Hi,

There are loads of questions in the stack.exchange site where users have problems with performance when they do something with reading and writing very large image files. Big files have obviously become much more common now due to clouds. Users try to solve the problem by increasing GDAL_CACHEMAX and using multithreading etc. but they use the default GeoTIFF settings and keep on writing huge striped TIFFs. I wonder if we should make tiling the default also for the GTiff driver like it is in the COG driver.

-Jukka Rahkonen-
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