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 :
Well explained and useful