[gdal-dev] Generating 200x200 tiles

[Homme Zwaagstra]

On 21/09/15 10:23, Alistair Young wrote:
> thanks for that. I downloaded the TFW and TAB files from the Ordnance Survey, put them in the same directory as the tif and did:  > > gdal_translate -of VRT -a_srs EPSG:27700 sx88.tif out.vrt >

The TFW and tab files should provide this the georeference and 
coordinate system
information.  This means you should just be able to skip the 
gdal_translate step
and use sx88.tif directly.  You can run `gdalinfo sx88.tif` to verify this.

> And ran ctb-tile on out.vrt. It tiled it but into what appear to be weird columns and rows. E.g. Col 14, row 16046 etc. The SDK fails to read this as I suspect it expects 20 cols and 20 rows (it’s 5 metres per pixel resolution)

The weird columns and rows reflect your use of the TMS geodetic profile.
Passing `-profile mercator` to ctb-tile will use the Mercator profile.  
I've not
used the OSGB SDK but if I had to guess I would assume it uses web 
mercator.

The resolution of the tiles will vary with the zoom level that you are 
looking
at.  When you say 'it’s 5 metres per pixel resolution' what are you 
referring to
by 'it'?

> I’m not sure what ullr is for. There’s no  information about the tif (it’s a British National Grid Square 20kmx20km) but I’ve no idea what lat/lon it covers.

ullr specifies the extent of the dataset. Assuming sx88.tif refers to 
the OSGB
national grid square SX88 (which would be 10kmx10km), your gdal_translate
command would be:

gdal_translate -of VRT -a_ullr 280000 90000 290000 80000 -a_srs 
EPSG:27700 sx88.tif out.vrt

As mentioned, however, the TFW and TAB files should provide this 
information.

If you need further help with using ctb-tile, it may be best to email me
directly rather than risk polluting the GDAL mailing list.

Best regards,

Homme.


>  > Alistair > > > ----------------- > mov eax,1 > mov ebx,0 > int 80 > 
 > From: <gdal-dev-bounces at lists.osgeo.org> on behalf of Homme Zwaagstra 
<hrz at geodata.soton.ac.uk> > Date: Monday, 21 September 2015 08:29 > To: 
"gdal-dev at lists.osgeo.org" <gdal-dev at lists.osgeo.org> > Subject: Re: 
[gdal-dev] Generating 200x200 tiles > > > > On 19/09/15 08:14, Alistair 
Young wrote: > > Thanks for that. I tried ctb but just got "Could not 
get transformation > information from source dataset². Chaning 
gdal2tiles to output 200x200 > worked ok but the SDK failed to display 
the tiles. I just have a 4000x4000 > >  tif with no geo referencing 
information so I can only generate raster > profile tiles. > > Alistair, 
you'll have trouble getting anything useful out of any geospatial > 
tools without inputting datasets that are correctly georeferenced with 
an > appropriate spatial reference system.  Assuming you know the 
extents of your > 4000x4000 raster, you should be able to do this by 
creating a virtual raster > with gdal_translate using options along the 
following lines: > >    gdal_translate -of VRT -a_srs srs_def -a_ullr 
ulx uly lrx lry in.tif out.vrt > > Passing out.vrt to ctb should resolve 
the error, and you'll have more chance > with other tools too. > > Best 
regards, > > Homme > > > > Alistair > > > ----------------- > mov eax,1 
 > mov ebx,0 > int 80 > > > > > On 18/09/2015 00:36, 
"gdal-dev-bounces at lists.osgeo.org on >  behalf of Brad > Hards" > 
<gdal-dev-bounces at lists.osgeo.org on behalf of bradh at frogmouth.net> > 
wrote: > >> On Thu, 17 Sep 2015 06:03:15 PM Alistair Young wrote: >>> 
I've been using gdal2tiles to generate zoom levels and tiles and it's 
 >>> working fine but unfortunately the tiles >  are 256x256 and don't 
work with >>> the UK Ordnance Survey mapping SDK, which requires 200x200 
tiles. Is >>> there >>> a way to generate these 200x200 tiles? I can 
generate them using >>> gdal_retile but it can't generate the zoom 
levels. >> I'd suggest just >  hacking the python script.  Make a copy, 
and edit the >> __init__() function to change the tileSize member init 
to be 200 vs 256. >> >> Worth a quick try at least. >> >> Brad >> >> >> 
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 >  >> gdal-dev at lists.osgeo.org >> > > 
http://lists.osgeo.org/mailman/listinfo/gdal-dev > > 
_______________________________________________ > gdal-dev mailing list 
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