Document and store a processing model with QGis 2.8

Document a model

Warning: The update of the help file does not work for
versions 2.8, 2.8.1 and 2.8.2.
A bug causes all changes performed with
the help editor to be lost.
Normally, the next update of QGis should
have this problem solved
.

You can inform the Model Help by clicking the
Model Help Editor button in the Graphic Modeller window.

This will open the Help Editor window that has three panels. At the top
is an HTML page with placeholders for the description of the algorithm, and
sections for the input and output parameters. At the bottom left you have an
element selection box, and at the bottom right, a text entry box. To edit an
item, select it in the left window and use the box on the right to enter a descriptive
text. Click OK when you are done.
This help information will then be available in the Help tab when
the tool is in run mode.

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Run and edit a processing model with QGis 2.8

Run a model

The model can be run in two ways:

  • from the graphical modeller window, or
  • from the Processing Toolbox panel .

To run a model from the Graphic Modeller window, click the Launch Template button :

To run a model from the Processing Toolbox panel, first save and close the model. Then, find the model by accessing Processing |Toolbox |Models , right click on the model to run and select Run in the context menu.

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The processing algorithms with the QGis 2.8 Graphic Modeller-Adding algorithms in the graphic modeller

The algorithms are added in   the graphic modeller as if they were data input. Simply select algorithms tab instead of Inputs data, to observe the corresponding display in the  Boxprocessingtool display.

Once the algorithm to be added is found, double- click, or glide toward the graphic window of the Modeller. To search the algorithm you can do it   as you would in the processing toolbox, typing the name in the search box at the top of the algorithm tab.

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ArcGis <-> QGis sharing data: the geodatabase file WORKING WITH THE GEODATABASES FILE ( .GDAL AND GDB) USING QGIS Posted on February 1st , 2015 by Nick Burkhart

Despite the very widespread false idea according to which the geodatabases file ( .gdb ) cannot be read and modified using tools within the Esri ArcGIS platform, recent versions of GDAL (and therefore using applications such GDAL- queQGIS ) are capable of, effectively, read and extract information from the geodatabases file . The geodatabase file format has become a very common format for storing and exchanging data space , in particular since it allows the storage of multiple data layers and that allows the storage of data layers exceeding the limits of others specifications . ArcGIS users, regularly, use geodatabases file when the attribute tables exceed the storage capacity of a shapefile attribute table ( a DBF file is limited to ~ 2 GB in size ).

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SpatiaLite databases with QGis 2.8 Wien tutorial

This tutorial provides you with the necessary steps to manage databases in QGIS. Although QGIS can handle several types of databases, we used SpatiaLite because it provides a lot of features without the need for a particular installation and very little administration work.
By using the database manager included in QGis, you can perform a certain number of database operations.
The main operations are: indexes creation, spatial and non-spatial views, import and export data, queries execution. After discussing the QGis database manager and the SpatiaLite usage guidelines in this tutorial, you’ll be well equipped to write more complex queries and take full advantage of the SQL and SpatiaLite SQL commands.

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Requests and views of a SpatiaLite database with QGis 2.8

One of the main differences between data management with shapefiles and a database is the ability to create different “views” for the same data. In this article, the last in the series devoted to SpatiaLite with QGis, we’ll discuss how to build SQL queries to generate SpatiaLite views.
DB Manager has a SQL window that allows the construction and execution of SQL queries on a database. This article shows how to use the SQL window to query a table and create a SpatiaLite spatial view.

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How to import tables into a SpatiaLite database with QGis 2.8

In a previous article we have discussed ( How to create  a SpatiaLite database with QGis 2.8 ) how to import a shapefile into a SpatiaLite database. The method is the same for other types of spatial data (kml, gml, …). We will now discuss how to import non-spatialized data (Excel, txt, csv, …) and especially those containing location attributes (XY, Lat / Lon, …) while creating their geometries. We will also discuss how to export SpatiaLite tables as shapefiles.

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Introduction to QGis 2.8 Toolbox

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:

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The ArcGis spatial-temporal cube: 1- discovery

One of the GIS areas where much remains to be done is the domain of time analysis. Indeed, if almost all the available tools focus on the spatial evolution of a phenomenon, one finds oneself quite helpless when it comes to visualizing or analysing a phenomenon that, also, evolves as a function of time.

We have had, for quite a long time,  animation tools that allow us to see a sequence of maps and perceive changes as a function of time. But, although useful for communication, these tools do not allow any serious data analysis.

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Model Builder: migration to ArcGis Pro

The ArcGIS Pro ModelBuilder is very similar to ModelBuilder in relation to the ArcGIS Desktop applications. The model diagram view is similar, and you build the models by adding data and geoprocessing tools   connecting them to shape processes. In ArcGIS Pro, you can view, edit, and run models that you have built in previous ArcGIS Desktop versions.

Despite these similarities, there are some differences. Knowing these differences will make your migration to use ModelBuilder in ArcGIS Pro easier.

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