[Qgis-user] Which android tablet

[Richard Greenwood]

As others have noted, your image performance is very bad. You can
convert your JP2 to TIFF with internal JPEG compression with
gdal_translate. You will get similar file size but I think much better
performance. Something like:

gdal_translate sourceImage.jp2 outputImage.tif -co COMPRESS=JPEG -co
PHOTOMETRIC=YCBCR

You can also use GDAL to add overviews (pyramid) with the following:

gdaladdo.exe --config COMPRESS_OVERVIEW JPEG -r average -ro --config
PHOTOMETRIC_OVERVIEW YCBCR --config INTERLEAVE_OVERVIEW PIXEL
sourceImage.jp2f 2 4 8 16 32 64 128

Rich

On Thu, Jul 12, 2012 at 4:11 AM, Tim Sutton <lists at linfiniti.com> wrote:
> Hi
>
> On Thu, Jul 12, 2012 at 12:01 PM, Bernhard Ströbl
> <bernhard.stroebl at jena.de> wrote:
>>
>>
>> Am 12.07.2012 11:48, schrieb watercress at gmx.de:
>>
>>> Hi,
>>>
>>> has anyone tested the performance of qgis on android.
>>>
>>> I want to collect and store the position of 50 trouts tagged with radio
>>> transmitters directly in the field.
>>>
>>>
>>> What I did so far:
>>> I have to aim at the targets from different locations at the river bank.
>>> What I do now is simply draw lines on printed orthophotos. The fish is
>>> located where the lines intersect. It is always quite a mess to
>>> determine your own position. I could save the origin with a gps-device
>>> but this takes too much time, would include "postprocessing" and adding
>>> another step will increase the source of error.
>>>
>>> ... and it is not possible to walk into the stream ...
>>>
>>>
>>> I am thinking of using a tablet, locally store the orthophotos (5 to 8
>>> pieces, format: .jp2, each around 130 MB) and save the points (e.g.
>>> postgis). All metadata could be entered at once. No paper work. I know
>>> where I am and can easily store, edit,.. fish data in the field.
>>>
>>> But I am bit worried about the performance. I takes about two til four
>>> minutes to load those raster-layers at my desktop (Ubuntu 12.04, 16GB
>>> Ram, QuadCore,...). The performance appears very poor.
>>
>>
>> This is weird. I am not a specialist with raster formats but one of my
>> aerial photos (geotif) 281 MB loads and displays within seconds, this is
>> with pyramids (maybe you need to build these?)
>> I even put some 50 of these photos into a GDAL virtual raster (VRT), it
>> takes some 20 seconds to load but displays almost immediately.
>> My machine is similar to yours hardwarewise (less RAM, though) running
>> OpenSUSE 64 bit.
>>
>
> I think the jp2 drivers are quite slow. A nice solution is to load
> your rasters into an mbtiles sqlite database - its not the best for
> size, but its very good for performance.
>
> Note it needs a recent (unreleased?) version of GDAL.. Otherwise
> convert your data to tiffs as Bernhard has done and optimise them for
> performace by e.g. creating pyramids.
>
> Regards
>
> Tim
>
>> Bernhard
>>
>>
>>>
>>> What can I expect from a tablet solution? Anything missing in my chain
>>> of thoughts?
>>>
>>> I really appreciate any hints, ideas ,..I also would like to contribute
>>> my experience as a case study for the qgis-website.
>>>
>>> Regards,
>>> Jens
>>> _______________________________________________
>>> Qgis-user mailing list
>>> Qgis-user at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/qgis-user
>>>
>>>
>>
>>
>> __________ Information from ESET Mail Security, version of virus signature
>> database 7291 (20120712) __________
>>
>> The message was checked by ESET Mail Security.
>> http://www.eset.com
>>
>>
>>
>> _______________________________________________
>> Qgis-user mailing list
>> Qgis-user at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/qgis-user
>
>
>
> --
> Tim Sutton - QGIS Project Steering Committee Member (Release  Manager)
> ==============================================
> Please do not email me off-list with technical
> support questions. Using the lists will gain
> more exposure for your issues and the knowledge
> surrounding your issue will be shared with all.
>
> Visit http://linfiniti.com to find out about:
>  * QGIS programming and support services
>  * Mapserver and PostGIS based hosting plans
>  * FOSS Consulting Services
> Skype: timlinux
> Irc: timlinux on #qgis at freenode.net
> ==============================================
> _______________________________________________
> Qgis-user mailing list
> Qgis-user at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/qgis-user



-- 
Richard Greenwood
richard.greenwood at gmail.com
www.greenwoodmap.com