[Qgis-user] [Qgis-developer] Projection of ESPG/ESRI

[Alex Mandel]

Right, that's because they have on the fly projection turned ON by
default. I thought at some point QGIS added a warning if it can't read
the existing proj, maybe you have to toggle it in your settings.

If we don't have that we probably should add it.

Like you though, I follow a general rule: Before doing any analysis
always convert everything to the same projection.

Projection on the fly is for data exploration and occasionally
cartography (though it can slow cartographic rendering and sometimes has
rendering errors when compared to reprojected data).

Enjoy,
Alex

On 11/27/2013 11:36 AM, Randal Hale wrote:
> Yeah - that's how I do it in ESRI but it tends to scream more with a
> undefined projection. QGIS just accepted it and moved onward - Luckily I
> haven't had any undefined things show up until I started deleting prj
> files trying to figure out what was going on with the EPSG:102667
> incident last night.
> 
> I appreciate the help.
> 
> randy
> 
> 
> -----------------
> Randal Hale, GISP
> North River Geographic Systems, Inc
> http://www.northrivergeographic.com
> 423.653.3611 rjhale at northrivergeographic.com
> <mailto:rjhale at northrivergeographic.com>
> twitter:rjhale
> http://about.me/rjhale
> 
> On 11/27/2013 02:31 PM, Alex Mandel wrote:
>> On 11/27/2013 11:18 AM, Randal Hale wrote:
>>> Awesome - OK - I didn't know project on the fly would assign a
>>> projection. I usually leave it off - All the data needs to be in one
>>> projection anyway.
>>>
>> No it's not that it assigns a projection, it's that it ignores the
>> projection and just operates on pure coordinates. So if you bring 2
>> things in that are different projections (ie a UTM layer and an unknown)
>> then unless they are actually the same projection they won't line up at
>> all.
>>
>> If you were to turn projection on the fly on, then the auto guess
>> incorrect WGS84 would do way screwy stuff even if both layers were the
>> same projection.
>>
>>
>> So basically, load up your unknown layer. Then load a known reference
>> layer. If it matches you have a winner, if it doesn't drop it and try a
>> different reference layer (different projection), and so on till you
>> find the match.
>>
>> Enjoy,
>> Alex
> 
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