[Qgis-user] Atlas generation - help please

[Alexandre Neto]

Hello Sergio,

If I understood you well, You have several layer\tables? One per specie?
Because that wasn't  the case study presented by John, where all species
were in one unique table\layer. If you have several layers, atlas won't be
able to iterate over them or turning them on and off for you without the
same amount of work that would involve making the species maps one by one.

Anyway, regarding the basemap, I'm not sure about what you are asking. but
you can create the grid yourself.

Alexandre Neto



On Fri, Sep 12, 2014 at 1:51 PM, Sergio Vignali <vignalisergio30 at gmail.com>
wrote:

> 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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