[Gdal-dev] SoC: GDAL2Tiles: georeferenced rasters on the web

[Frank Warmerdam]

Petr,

I've read your three related messages over, and also thought a bit about
our discussion along with Adam Nowak in IRC.

My hope for this project was that we could have a read-write GDAL driver
that would support at least one "web tiled format" and ideally more than
one.

After discussions in IRC it seems that the naming conventions for TMS,
GQT and WorldWind are all distinct but that associated Google Earth kml
files could be generated for any of them.

I don't see too much benefit in targetting GeoQuadTree since there is a
limited amount of client interest in this.  However, with the agreement
to dual license GQT, I would like to see support for it incorporated into
GDAL.  This doesn't have to be part of your project, though I can see
that aspects of the GQT GDAL driver might be educational for you.

This leaves us with the decision of whether to use the WorldWind or
TMS tile naming convention as our basic tiled organization.   I'm inclined
to chose TMS since it gives us convenient support within clients like
OpenLayers, Worldkit and Cadcorp SIS.

If so, I would see your primary objective for the summer as writing
a GDAL driver that supports writing a tiled raster format that is
TMS compatible and Google Earth compatible.

I would also like the driver to be able to read these datasets (if
produced by GDAL) even if you need to write some sort of extra metadata
file at the root to make this easier (and less lossy of metadata) as
well as supporting "in place update".  That is to be able to open the
dataset in update mode and replace parts of the imagery on demand.
This also implies implementing the GDALDriver pfnCreate function
instead of (or at least in addition to) the pfnCreateCopy function.

I'd suggest you not try to address reproject in your project.  Assume
that gdal_merge, gdalwarp, or whatever will be used to handle
mosaicing or reprojection.  Although I would note that implementing
read/write/update support in the driver will make it possible to
mosaic additional images into an existing mosaic using something like
gdalwarp.

Additional optional objectives for the summer might include:
  o Producing whatever is needed to use the dataset with google maps.
  o Tweaking options for the driver such as supporting a wide variety
    of file formats for the tiles, tile sizes, compression options,
    extra metadata.

Does this seem reasonable?

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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