[Qgis-user] OnTheFly Reprojections

[Jonathan Moules]

One further thought on this - is it supposed to be so incredibly slow?
Especially given it's basically only reprojecting from/to the same
coordinate system (with a few decimal places of difference). I know that if
I open things in different projections in ArcGIS there's no noticeable lag.
Cheers,
Jonathan



On 24 February 2014 13:58, Jonathan Moules <
jonathanmoules at warwickshire.gov.uk> wrote:

> Thanks for the responses. I think that's going to have to be the longer
> term plan.
>
> Jonathan
>
>
>
>
> On 21 February 2014 18:46, Etienne Tourigny <etourigny.dev at gmail.com>wrote:
>
>> In this case you a probably better of making copies of the files with all
>> the same CRS.
>>
>>
>> On Fri, Feb 21, 2014 at 11:41 AM, Jonathan Moules <
>> jonathanmoules at warwickshire.gov.uk> wrote:
>>
>>> Hi List,
>>> Two issues,
>>>
>>> First, I'm noticing that quite a few of the layers we have that are in
>>> British National Grid aren't actually treated that way when I load them
>>> into QGIS. This seems to be because they have a very slightly different
>>> definition than the one QGIS has.
>>> For example:
>>>
>>> +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000
>>> +y_0=-100000 +ellps=airy +towgs84=375,-111,431,0,0,0,0 +units=m +no_defs
>>>
>>> +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000
>>> +y_0=-100000 +ellps=airy
>>> +towgs84=446.448,-125.157,542.06,0.1502,0.247,0.8421,-20.4894 +units=m
>>> +no_defs
>>>
>>> QGIS definition
>>> +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000
>>> +y_0=-100000 +ellps=airy
>>> +towgs84=446.448,-125.157,542.06,0.15,0.247,0.842,-20.489 +units=m +no_defs
>>>
>>> Three different definitions for the same thing.
>>> This becomes a problem because On The Fly reprojection (which I've now
>>> been forced to disable permanently) is super slow. Even a simple polygon
>>> layer with a few dozen features on top of a WMS creates a very noticeable
>>> (several seconds) lag.
>>>
>>> So my question:
>>> Is it possible to make QGIS recognise all the different definitions as
>>> one single definition?
>>>
>>> Using a Master build from a couple of months ago.
>>>
>>> Thanks,
>>> Jonathan
>>>
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>>
>>
>

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