[Qgis-user] Atlas generation - help please

[Sergio Vignali]

Hi Alexandre,
many thanks for your explanation! This is the first time I use the atlas
generation and I begin to understand how it work. But I have another
question, you suppose to have several point layers of species distribution,
but all in the same area, so in this case you need to have a basemap good
for all the species but you want to change only the points above the
basemap. Something like the Atlas of species distribution in which you have
a basemap with an utm grid and above a dot only in the square where the
specie occurs.
This is what I'd like to do, I have all the data in a postgis database
where I have also several tables with the centroid of the square in which
the specie occurs.
What solution you suggest?

All the best

Sergio

2014-09-03 15:51 GMT+02:00 Alexandre Neto <senhor.neto at gmail.com>:

> Hello all,
>
> On Mon, Sep 1, 2014 at 9:52 PM, Nyall Dawson <nyall.dawson at gmail.com>
>  wrote:
>
>> I'm 99% certain that what you are after is possible in QGIS 2.5 (the
>> unreleased development version of 2.6). But do you mind posting this
>> question over at gis.stackexchange.com with some screenshots of your
>> data format so I can be certain? I'll send through a step by step answer
>> over at stack exchange with screenshots for you.
>>
>> Cheers,
>> Nyall
>>
>
> Nyall, I think I will post the question myself, as I'm curious about how
> is the correct way to do this in QGIS 2.5 :-P
>
> On Tue, Sep 2, 2014 at 12:30 PM, Sergio Vignali <vignalisergio30 at gmail.com
> > wrote:
>
>> Hi Alexandre,
>> you say that you know a way to do that with postgis,
>> please could you explain that?
>>
>
> Sergio, not really, it would still need qgis help. Postgis would only
> facilite things (see below).
>
> On Wed, Sep 3, 2014 at 1:18 PM, Thomas Colley <
> t.colley at neath-porttalbot.gov.uk> wrote:
>
>> How about creating a polygon layer with a bounding polygon for all points
>> per species? The polygon features would have the species name as an
>> attribute.
>>
>>
>>
>> You can then use this polygon layer for your atlas and use rule based
>> styling to filter the points based on the species name attribute of the
>> atlas feature.
>>
>
> Like I said before I think this is not possible since you cannot access
> the atlas feature atributes from the expression builder, but the idea was
> that one. Using postgis would just make the task of creating the polygon
> layer for each specie easier.
>
> Meanwhile, talking with Giovanni Manghi, he came up whit a workaround idea
> that can actually work quite nice.
>
> One thing you can get from the atlas feature is the feature id (that
> represents his position on the table). So instead of using the specie name
> attribute, one could use this ID.
>
> Having a layer with a bounding polygon for each specie, with a column with
> the specie name, I would do the following:
>
> - Using field calculator, add a new column (boundary_id) in the boundary
> polygons layer (the one that will be used in atlas) with it's ID using $id;
> - In the data layer (the one with all species presences) join the boundary
> polygons layer using the specie name;
> - Now use the rulebased symbology on the data layer to filter only the
> points where "boundary_id" = $atlasfeatureid
>
> Runing atlas generation with the boundary polygons layer, should do what
> is asked.
>
> The caveat of this procedure is that any change on the dataset (for
> example adding a new specie, or removing all presences from another) would
> require changes in the  boundary feature. This can originate id changes,
> and to make sure all spicies maps are printed , one should repeat all the
> steps described before. But, that's much better than doing the map on by
> one!
>
> BTW, I don't think any other GIS software allow this kind of interation
> and filtering. Can anyone comment on that?
>
> Best regards,
>
> Alexandre Neto
>
>


-- 
Sergio Vignali
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