[gdal-dev] GDAL WKT Raster Driver weekly report #5

[Jorge Arévalo]

Hello Frank,

2009/6/30 Frank Warmerdam <warmerdam at pobox.com>

> Jorge Arévalo wrote:
>
>> Hello,
>>
>> This is the report #5 of GDAL WKT Raster driver:
>> http://www.gis4free.org/blog/2009/06/27/gsoc-09-weekly-report-5-1906-2606/
>>
>> The project can be followed here:
>> http://trac.osgeo.org/gdal/wiki/WKTRasterDriver
>>
>
> Jorge,
>
> I appologise for not staying on top of my mentoring duties.  I am reviewing
> the design document at:
>
>
> http://www.gis4free.org/blog/wp-content/uploads/2009/06/gdal-wktrasterdriver-spec-0.2.pdf
>
> Is this still the most current version of your design?  I see Even,
> Mateusz,
> Pierre and others have provided some feedback.  Their comments seem good.


Don't worry. As you said, this is not the current version. Even, Mateusz,
Tamas... and myself, have commented a lot of things that must be added.


>
>
> I would also support the suggestion to put the design in a more malliable
> form, such that others can contribute more directly - such as a trac wiki
> page. I also think the design needs some further updates from the 0.2
> version.  I notice you have your own trac now, though it does not seem to
> have any public access which I think is unfortunate. Don't hesitate to keep
> the design in the GDAL trac.


OK. I'll use the GDAL trac to create a web version with more information.

>
>
> I would like design to better address the relationship between WKTRaster's
> data model and the GDAL data model.  So, for instance, you might note
> things
> like:
>
> 1) The fPixelSizeX, fPixelSizeY, fUpperLeftX, fUpperLeftY, fRotationX,
> fRotationY values will become the GeoTransform in GDAL, possibly noting
> how the transformation will take place.   Actually, the f* fields I note
> are actually on a single WKTRaster objects after fetching and instead
> you really need to populate the Geotransform based on the extent,
> pixelsize_x
> and pixelsize_y fields from the RASTER_COLUMNS table and that
> for now only north up images will be supported (unrotated).
>
> 2) Note that WKTRaster uses an SRID lookup into the spatial_ref_sys which
> may contain WKT and PROJ.4 representations of a coordinate system, but
> that GDAL needs WKT.  Note perhaps that the spatial_ref_sys lookup code
> from the OGR PG driver can be used essentially unchanged, and that things
> only get messy when there is a need to create new rasters as it is
> sometimes
> hard to establish what SRID to use for a given WKT (or whether to create a
> new one), but that this matter can also be done using the same approach as
> the OGR PG driver.
>
> --
>
> In general I was surprised to find no mention of the RASTER_COLUMNS table
> and the implications for the WKTRaster driver.  To a significant extent
> this table was defined to make it easier to write the WKTRaster driver.
> It encapsulates a concept of simplistic rasters that can be easily mapped
> onto the GDAL data model and that can be efficiently manipulated by GDAL.
>
> I would like the design talk about steps in implementation.  The first
> complete step should be a read-only driver that supports
> "regular_blocking" type images defined via RASTER_COLUMNS.   I would
> hope this would be accomplished by the mid-term review.
>
> After that some additions you could work on are:
>
>  1) Supporting rasters that are not "regular_blocking".  I think it will
>    be hard to make this really efficient, but it is definately doable.
>
>  2) Support in place update for existing rasters.
>
>  3) Support creating new rasters.
>
>  4) Support access to overviews.
>
>  5) Support "outdb" rasters.
>
> I would like a sense of which of these you hope to do this summer,
> in what order, and what you see as the issues with them.
>
> I would personally be quite happy if you did a bulletproof and efficient
> implementation of read-only access to WKTRasters with overviews and
> all applicable metadata and access to "outdb" rasters.
>
> Make sure the project plan includes time to extend the python test suite
> with tests for the WKTRaster driver, and to write up user driver
> documentation.
>

Understood. Since now, I'm working on an extended version of the document
(1.0 this time), describing more in detail all the work,  including your
comments, and any other information that can be useful.

Many thanks for your comments, I'll keep you (and the list) informed.

Best regards
Jorge


>
> --
>
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam,
> warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | Geospatial Programmer for Rent
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/gdal-dev/attachments/20090630/ee9faf48/attachment-0001.html