Re: How transform specific geometry column using Django GIS GeoQuerySet

[Alex Mandel]

On 03/26/2014 06:28 AM, Shoaib Ijaz wrote:
> Sorry i mistype queries
>
> Network.objects.transform(srid=3857).values('geometry', 'bbox')
>>
>> SELECT ST_Transform("tbl_network"."geometry", 3857), "tbl_network"."bbox" FROM "tbl_network"
>>
>> Network.objects.transform(srid=3857).values('bbox')
>>
>> SELECT "tbl_network"."bbox" FROM "tbl_network"
>>

You might get more responses on the GeoDjango mailing list:
geod...@googlegroups.com

I think you syntax might be wrong.
https://docs.djangoproject.com/en/dev/ref/contrib/gis/gdal/#coordtransform

But since your mixing django code and SQL code it's hard to tell what
your doing.

Thanks,
Alex

[Alex Mandel]

On 03/27/2014 04:53 AM, Shoaib Ijaz wrote:
>
>>
>> I am doing sql queries in django, the queries that i mentioned above are
>> print queries of django

>
>
> Network.objects.transform(srid=3857).values('geometry', 'bbox')
>

> *This is printed SQL query output of above django query *

>
> SELECT ST_Transform("tbl_network"."geometry", 3857), "tbl_network"."bbox" FROM "tbl_network"
>
> Network.objects.transform(srid=3857).values('bbox')
>

> *This is printed SQL query output of above django query *

>
> SELECT "tbl_network"."bbox" FROM "tbl_network"
>
>

I see so the 1st query works and the 2nd one fails to do the transform.
I think the problem may be related to you having 2 geometry columns in
the same Postgis table.

Are both of them listed in the geometry_columns view of Postgis.
Typically only 1 can be the default. In this case geometry, so
Geodjango/Postgis is recognizing it as a spatial column. But when it
get's to bbox it doesn't recognize it and doesn't know what the FROM
(current) srid is so a Transform wouldn't work.

One option would be to return the data and then transform it once you
have the spatial objects into python variables.

Thanks,
Alex

[Shoaib Ijaz]

Can you elaborate following statement, i am at beginner level in django what why i cannot understand your reply

   One option would be to return the data and then transform it once you  have the spatial objects into python variables.  

   Thank you