When we need to use a tool of the QGis toolbox, it is
usually
in
the heat of the moment and we omit some preliminary
configuration points . As usual,
at one time or another we will have to come back to lift a blockage .
So here are a few
tips to be aware before getting started with the toolbox.
The processing toolbox serves as a portal for accessing specific processing to QGis but also for third-party providers . Historically , processing from other GIS packages was only accessible with the third party software environment or through a command line environment. The processing toolbox allows running directly third party processing from the QGis interface. The following suppliers processing are accessible using the toolbox:
• geoalgorithms of QGIS
•
GDAL / OGR
•
GRASS
•
SAGA
•
TauDEM
•
LAStools
•
R
•
Orfeo Toolbox
•
Models
•
Scripts
The last two lines are not third party packages, but refer to the models you can create with the QGis graph modeler and PyQGis scripts that you can create with the Python Console.
How to format the processing toolbox
Firstly, we will make sure the processing
toolbox is correctly formatted
to access and
run
the GRASS, SAGA, TauDEM and LAStools algorithms . Most
libraries required are installed
automatically
, but the configuration of these tools
vary
according
to the operating system and to how you have installed
QGIS.
For
example , if you have
used
the
OSGeo installer
you can use the Installation
advanced option to install GRASS 7 otherwise
you
must
manually install GRASS 7 and configure the directories
in
the toolbox.
If
you cannot find a configuration option in the toolbox for a given package, it
means it is not installed .
Refer
to http://docs.qgis.org/2.6/en/docs/user_manual/processing/3rdParty.html for
details installation of different third-party
libraries .
The toolbox formatting includes essentially the activation or deactivation of a library , as well as the definition of the directories used. To open the formatting window you must click on the menu Treatment-> Options …
To start, you must ensure that each of the libraries you plan to use is activated and, according to your operating system and installation chosen , you will, perhaps, specify the necessary directories to execute TauDEM , LAStools , and R. The following figure shows that each of the libraries is activated and that the directories required are thoroughly specified .
Clicking OK updates the display of the toolbox. If you do not use some libraries simply uncheck the Activate box. This simplifies the toolbox.
Overview of the toolbox structure For the time being, we have not really discussed the interface. We have simply formatted an perhaps, installed the libraries required to make the function available in the toolbox. To display the toolbox, you must click on the Process menu ->Toolbox
The processing toolbox appears on the right side of the QGIS interface .
However, by default, most providers algorithms are not visible. You must click on the option Simplified interface that is located the bottom of the toolkit window, scroll through the available options and select so display advanced .
After selecting the advanced interface option , finally, you will gain access to the algorithms complete list toolbox:
At first, you see a list of various libraries and the number of available algorithms in each of them . When you click the + next of entries, the list expands to display the subdirectories that bring together different tools . In addition to browsing manually through these directories, there is a search field at the top of the toolbox. If you are already familiar with libraries and you look for a specific tool, this can be a more efficient way to access the algorithms . Even if you are not familiar with the libraries, you can always use the search box to discover which are the available tools. For example , if you are interested in the different ways to visualize or explore the topographic relationships , you might search by typing ” topograph ” in the text box and discover that there are ten tools from three different suppliers that relate to the topography .
To launch a processing, you just have to double click on its name in the toolbox window. The setting window opens automatically . The processing toolbox provides, also, an additional option allowing access to underlying processing. To that end, you can open an online command window by clicking on the Process menu ->CommandLine.
It should be noted that by typing “grid” in the search box , you get a list of the available algorithms concerning the grids. The main difference between the two types of research is that when a tool is selected in the drop list of the command line, it opens automatically . Therefore, once you have a certain degree of familiarity with the names of the specific tools, the command line can increase, significantly, your productivity . Now that the QGIS processing toolbox is correctly formatted and that you have an idea of how it works and its overall organization , you can start using it and you will save a few blockages !
