[gdal-dev] Tiled GeoTiff that reduce the amount of reads in XYZ maps

[Even Rouault]

On dimanche 17 juin 2018 10:19:34 CEST Guy Doulberg wrote:
> Hi all,
> 
> I am trying to use cloud optimized geotiff(cog) to reduce the block fetched
> when accessing a raster.
> 
> The use case I am trying to build, is a TileServer that serves tile in
> openlayer map.
> The rasters are to be stored on a remote location, in my case azure blob
> storage.
> 
> We were able to do that, and you can see the code here:
> https://github.com/satellogic/telluric/blob/master/telluric/
> georaster.py#L1497
> 
> The problem is, when running in verbose mode I can see that there are many
> requests to the blob storage,
> 
> I am responsible of creating the raster, is there a way in your opinion I
> can create the raster aligned to the XYZ tiling system so when I try to
> fetch a tile from the raster I will be able to do that with a single or
> close to that call?

If your raster source is not already in WebMercator projection, you could use 
gdalwarp with the appropriate -te and -tr to align on the boundaries of XYZ 
tiling scheme at a given zoom level.

If your raster is already in WebMercator, gdal_translate -projwin -tr would do

If you don't want to compute the bounds, you could use gdal_translate to 
MBTiles that will use gdalwarp internally to reproject and align on XYZ tiling 
scheme automatically, followed by gdal_translate to TIFF with -oo 
USE_BOUNDS=NO so that the extent used aligns on tile boundaries.

Even

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