How to build an Atlas with QGis

The purpose of the Atlas function is to automate
the production of a series of maps. You
create
a
model,
a series of geographical areas and this
function
produces
automatically for each area.

We will discuss the necessary concepts
to put it into practice.

Firstly
, when you
open
a
new
project, you obtain, also, a set manager for empty pages . 

You must start by creating
your
project
: load the data in the cartographic window,
select the desired symbology for each layer
, etc.

Then you will create the desired page
layout with the page layout manager where you will
have the map(s), legend, titles and texts , scale bar , etc.

The only thing to remember at this moment
is
that you must create a
page layout setting that can be
used
for each section of your working area. The
easiest way is to zoom in one of the desired maps and to format the layout page
setting by, always, using this
zoom
level . You
must work as if
your only goal were to
obtain, as output, nothing but that map.

Once satisfied with your
layout page setting, the real Atlas creation starts.

How to create
the
Atlas master layer.

This layer must
contain
the entities that will serve to define the extent of each map of the
Atlas . Forcibly, it has to be “polygon type” .

Green areas can do the trick .
Each
output map will have the same scope and
scale
. But the layer of communes can,
also, be used . In this
case,
each map will be centred in one commune, alternatively. They
will
have different scales or you
can
set
up a parameter to
determine a common scale for all the maps.

This layer does not only contain
the extend of each map of the Atlas . It contains, as
well, all the variables associated with each map.
For example , if you would
like that each map of green areas to have a different title , a text attribute
for each entity, containing the text to be used when creating
each map, will be needed.

How to set
up the Atlas function

In the page setting manager,
when you
have
formatted
your output, click on the tab ”   Atlas
  ”  

Go
to the function setting.  

Check the Create an Atlas
box to start the function.

The Setup panel allows you to set up the Atlas operating
options:

1- Coverage layer: select
the Atlas master layer with the areas corresponding
to each map.

2- The option Hide the
cover layer stops the
printing of the entities of the master layer mistress
in your maps.

3- The Page name is
an attribute of the master layer used to identify the maps in
the format manager. It is not used for the outputs.
  

4- The option Filter with
allows creating a filter on the master layer.
This allows you to
use a single master layer
for
several different Atlas, by selecting through filtering the entities to be taken
into
account
for the creation of cards.

5-The Order By option
allows
to determine the sequence of maps. By default, if this
option is not used , maps will be produced
according
to the order of the recordings of the master layer.

The Output panel is used to give structure to the file name of each map, if you want a file by map. You can, as well, check the box to produce one single file with the set of maps . The first option applies, for example, to a series of images png , while the second applies mostly to a files pdf.

How to display the Atlas

In the format manager menu page,
click Atlas and Atlas Overview.
The
following menu options: First entity ,
Entity previous ,
Entity Next , Last
entity are activated
. They allow you to display in the format manager
window on each page of the Atlas maps.

The other menu options allow you , once the setting up is
finished,
to achieve the desired outputs: individual maps or
single
file

How to set up
the Atlas variables

You can personalize
all
the Atlas maps across variables. The most common need
is
the customization of the title of each map.

Therefore , you must create
a
Title
element in your page
setting. In the text window of the item, you can
enter
the classical text and references for one or
many
attributes
of your master
layer .  

In this example
we are referring to an attribute named Title2.
The
fact of delimiting the by [% and %]
identifies
it as a variable to be replaced by a
value
when creating the Atlas. The variables are as
well, replaced when viewing the Atlas with
the Atlas Preview.

But the variables are not
limited to the textual elements of the page. You
can
use the Atlas variables anywhere in QGis :

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