geo_minx,geo_miny.. and extent_minx, extent_miny difference?

[Majid Hojati]

Hi,

Can you please explain a bit about these fields in raster_coverage table?They are the same for SRID=4326 but Does they face any difference when we change SRID?

As I guess fields with geo must refer to geographic coordinates but those which start with extent are based on native SRID of covarage, is it right?

thanks

[mj10777]

On Monday, 25 September 2017 21:57:04 UTC+2, Majid Hojati wrote:

Hi,

Can you please explain a bit about these fields in raster_coverage table?They are the same for SRID=4326 but Does they face any difference when we change SRID?

To understand this properly you must know that the main intention was that RasterLite2 would be WMS capable.

So many aspects that you see  are that they are needed for a WMS Server.

- one can assume that 99,9% of WMS servers understand what WSG84 is and after a GetCapabilities request an area in Wsg84 without any extra Transformations.

As I guess fields with geo must refer to geographic coordinates but those which start with extent are based on native SRID of covarage, is it right?

Yes, that is correct. 

thanks

[Majid Hojati]

Dear Mark,

Thanks very much,

[a.fu...@lqt.it]

On Mon, 25 Sep 2017 13:11:32 -0700 (PDT), 'mj10777' via SpatiaLite
Users wrote:
> On Monday, 25 September 2017 21:57:04 UTC+2, Majid Hojati wrote:
>
>> Hi,
>> Can you please explain a bit about these fields in raster_coverage
>> table?They are the same for SRID=4326 but Does they face any
>> difference when we change SRID?
>
> To understand this properly you must know that the main intention was
> that RasterLite2 would be WMS capable.
> So many aspects that you see  are that they are needed for a WMS
> Server.

the whole RasterLite2 has a general design closely inspired by the
WMS technical specifications, and there are several good reasons for
adopting such an approach:

- WMS is an international standard; it was initially introduced by
OGC (Open Geospatial Consortium) but it was finally adopted by
ISO itself (ISO-19128), so it's now a mandatory normative
reference for any industrial branch, not only for GIS tools.

- WMS was initially conceived for WebServices, but its conceptual
model can be easily adapted so to support an innovative approach
fully based on SQL functions more than on classic C/C++ API

- last but not least, WMS is extensively and detailed documented;
and when designing an innovative library just relying on an
already existing and well established technical specification
is surely better that "reinventing the wheel" yet another time.

If you are curious to learn more about WMS you can get for
absolutely free all the technical specification documents
from here:

http://www.opengeospatial.org/standards/wms

bye Sandro

[Majid Hojati]

Dear sandro, 

Thanks very much for the reference, In fact now I have faced an image wide and hight determination problem, I know that I must set these parameters base on requested area but It does not give me any results, can you please help me in this case?

I have explained it in this related topic

https://groups.google.com/forum/#!topic/spatialite-users/pCVoXat8bwY