[Qgis-user] spatialjoin

Wed Dec 21 10:23:10 PST 2016

Hi,

i thought it was more easy ...

In fact , i don't use a GPS because these points don't need precision : 
they are only used to identify the parcels . And i would like to catch 
their identity ( a number for each parcel and the owner ) if possible 
with a dynamic spatialjoin...

With booth data ( number of parcel and name of owner ) , i could talk 
with the fisc administration :-)

Randy was right ...i didn't have the same EPSG for the two layers . It's 
now OK ! but without the feature "dynamic" .

Indeed , i would avoid building many temporaries layers and i thought it 
existed a plugin for this  " dynamic" feature.

If no , i will ask my users to make spatialjoins some time to time ...

Waiting , i will try the solution of Bernd...

Thank you anyway !

laurent

Le 21/12/2016 à 17:46, Bernd Vogelgesang a écrit :
> Hi,
>
> for me this sounds more like he is getting new points once in a while and
> wants to join those attributes to the new points "automatically" from the
> parcel layer.
>
> The biggest problem for users is to rethink the workflow from the end to
> the beginning and to know the limitations.
>
> The outcome should be a point layer with the polygons attributes. If 
> those
> points (layer A) are from GPS as Randy assumes, they have to be
> reprojected to the parcels layer (layer B) before being able to join them
> spatially(layer C). The spatial join in the toolbox produces layer D.
>
> Most probably, the resulting layer D is going to to be edited in some way
> (adding notes about size, the progress, classifications, whatever), so 
> you
> will have to find a way to preserve those new attribute while being 
> able to
> add new points without much trouble.
>
> The processing toolbox is a good way to do these steps, though it 
> produces
> a lot of temporary files cluttering the project.
>
> A better way for all those repetitive tasks, is to use the graphical
> modeller, to create a workflow which only has to be triggered once new
> points come in, and the resulting file can be saved as new a file e.g.
> with the current date in the name, so you have kind of an archive and 
> do not
> overwrite previous files (and destroy your work in case something goes
> wrong).
>
> So I can imagine a model with input layer A (new points in WGS84 
> without attributes) and a parcel layer B (in whatever projection).
> reproject layer A and C will be created as an intermediate step.
>
> Next input layer is the latest result layer D, reprojected and with 
> attributes.
> Merge layer C and D -> E. Now delete all columns which are from layer 
> B (from the last spatial join. Unfortunately, you can only delete one 
> field at a time in the modeller, so you'll will have to add the 
> command several times in a row to the model) -> Fn
> Do the spatial join of Fn with B.
>
> The last result G will now hold all points with the corresponding 
> parcel info plus additional fields you might have added to the points.
> G will be the input D in the next run with fresh points.
>
> So, do not add new points to the already existing collection of points 
> in WGS84 (it is never save to edit layers without backup), but just 
> import them as a new input set and then run the model with the parcel 
> layer and the last result layer.
>
> The modeller is not as intuitive as it should be, but it can save you 
> a lot of time once you managed to set up a model.
>
> Maybe I was completely wrong analysing the problem, but maybe someone 
> else has the problem that fits to my solution ;)
> Cheers
> Bernd
>
>
>
>
>
> Am 21.12.2016, 14:07 Uhr, schrieb Randal Hale
> <rjhale at northrivergeographic.com>:
>
>> 2 things:
>>
>> 1. In QGIS there is a processing toolbox (I assume you are one 
>> something as new as version 2.14.8). Open it (it's at the top -> 
>> Processing -> Toolbox). You can search for tools. Search for "join" 
>> and you should see a "Join Attributes by location". This is a spatial 
>> join.
>>
>> 2. THE MOST IMPORTANT THING. You mentioned you had collected points 
>> with a GPS. Possibly these points are in EPSG:4326. I'm going to 
>> guess that your parcel layer isn't. If you right click your parcel 
>> layer (in the layers panel) it will allow you to select properties. 
>> On the General Tab you will see the Coordinate Reference System 
>> mentioned and many times it is something like EPSG:xxxx . A Spatial 
>> Join must have the layers in the same coordinate system.
>>
>> If it is different - Right Click on your GPS points and "Save as". 
>> When the "Save vector layer as...." window comes up. Save it as a 
>> shapefile and MOST IMPORTANTLY change the CRS to match your parcel 
>> layer. Click on the small globe (that appears to be wearing a hat) 
>> and in the filter type in the number you see for your parcels. You 
>> can then select that projection and Save your file. It should save. 
>> You can then perform the "join by location".
>>
>> It should work. You are very close though so don't worry.
>>
>> Randy
>>
>>
>>
>> On 12/21/2016 01:24 AM, Erwan Conseil wrote:
>>> Hi
>>> In my layer B , I have the name of the owner and the number of the 
>>> parcel : this number , a polygon , have a WKT location . All this is 
>>> in a SHP . As I grab points in layer A directly in Qgis (2.18) , I 
>>> have also a SHP . And i need a dynamic join because I have no desire 
>>> to make the spatial join each time...
>>> Regards
>>> Laurent
>>>
>>>> Le 21 déc. 2016 à 01:30, Randal Hale 
>>>> <rjhale at northrivergeographic.com> a écrit :
>>>>
>>>> In your layer B - Do the Names of the Owners have a location (like 
>>>> a tax parcel) or are they a spreadsheet (like Microsoft Excel)?
>>>>
>>>> Randy
>>>>
>>>>
>>>>> On 12/20/2016 06:03 PM, Laurent Bourlet wrote:
>>>>> Hi at all
>>>>>
>>>>> I'm a beginner in Qgis and i would make a dynamic spatialjoin.
>>>>> In fact , i have created a vector layer ( for example  A) and i 
>>>>> grab points in it when I'm outdoor ( these points are buildings 
>>>>> unknowned by the government and so these building are not taxed 
>>>>> ...) . I have also a layer (B) with the name of the owners of 
>>>>> these lands .
>>>>> You see what i would ?...
>>>>> I would have these names transferred as attribut from B to A .
>>>>> For that , i think about a spatialjoin with a dynamic feature . So 
>>>>> i have downloaded the two plugins "reffunction" and "spatialjoin".
>>>>> But i have certainly maked something wrong because i don't succeed 
>>>>> ...
>>>>>
>>>>> Is it the good method ?
>>>>>
>>>>> And If yes , and if exist a doc about these plugins ...i'll take 
>>>>> it :-))
>>>>>
>>>>> regards
>>>>>
>>>>> Laurent
>>>>>
>>>>> ( pour les francophones ...je repère et saisis des points 
>>>>> représentants  des batiments construits et visibles par Google Map 
>>>>> mais inconnus par le cadastre et donc les impôts ...je voudrais 
>>>>> donc enrichir la couche de saisie par les références des parcelles 
>>>>> et les noms des propriétaires par une jointure spatiale dynamique 
>>>>> ..à chaque point saisi , "monte" cette référence )
>>>>>
>>>>> _______________________________________________
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>>>> -- -----------------
>>>> Randal Hale
>>>> North River Geographic Systems, Inc
>>>> http://www.northrivergeographic.com
>>>> 423.653.3611 rjhale at northrivergeographic.com
>>>> twitter:rjhale
>>>>
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