[postgis-devel] [WKT Raster] Regular blocking in gdal2wktraster.py

[Pierre Racine]

I now better see your point: What if regular_blocking is set to false but still, tiles are not overlapping and are then proper for such an application?

Good question.

Probably we should split the regular_blocking flag in three:

-same_size: tiles are all the same size and blocksize_x == blocksize_y
-overlap: at least two tiles overlaps
-firsttileupperleft: the tiles are ordered in the table as they should be ordered in a file. (I'm not sure this can be garanteed by a select statement)

(Is this sufficient?)

if same_size && ! overlap && firsttileupperleft then regular_blocking = true

Really, I find this regular_blocking constraint, constraining :-( :-)

Pierre

>-----Original Message-----
>From: postgis-devel-bounces at postgis.refractions.net [mailto:postgis-devel-
>bounces at postgis.refractions.net] On Behalf Of Pierre Racine
>Sent: 27 mars 2009 14:19
>To: PostGIS Development Discussion
>Subject: RE: [postgis-devel] [WKT Raster] Regular blocking in gdal2wktraster.py
>
>Well, if your application does not support display of overlapping objects then you should not store
>overlapping tiles in your db... As if your application does not supports tiff then you should probably
>not store your data in tiff... It is not because some applications do not supports fonctionalities
>that we most stop developping functionalities. Overlapping rasters exist and they will always exist.
>Most desktop applications are able to display overlapping rasters. Your application would take for
>granted (checking first with SELECT regular_blocking FROM raster_columns WHERE name="mycoverage") that
>tiles are not overlapping.
>
>Pierre
>
>>-----Original Message-----
>>From: postgis-devel-bounces at postgis.refractions.net [mailto:postgis-devel-
>>bounces at postgis.refractions.net] On Behalf Of Mateusz Loskot
>>Sent: 27 mars 2009 14:03
>>To: PostGIS Development Discussion
>>Subject: RE: [postgis-devel] [WKT Raster] Regular blocking in gdal2wktraster.py
>>
>>Pierre Racine wrote:
>>> Does applications like Google Earth profit from regular blocking?
>>> Why is it better to query for
>>> regular blocked tiles in chunks than just querying for tiles with a
>>> proper SQL query and display them as independent raster forming a
>>> layer? This is the way vector layer works and nobody complains.
>>
>>
>>There is coverage composed of two overlapping tiles
>>(size of tiles does not matter now):
>>
>>+--------+
>>|        |
>>|  +-----|------+
>>|  |     |      |
>>|  |     |      |
>>+--+-----+      |
>>   |            |
>>   +------------+
>>
>>(I hope my ASCII-art format is preserved)
>>
>>How do you render it in a basic client (desktop, web, whatever)?
>>
>>--
>>Mateusz Loskot
>>Senior Programmer, Cadcorp
>>http://www.cadcorp.com