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SAGA Quickstart
SAGA (System for Automated Geoscientific Analyses) is an open source geographic information system (GIS) used for editing and analysing spatial data. It includes a large number of modules for the analysis of vector (point, line and polygon), table, grid and image data. Among others the package includes modules for geostatistics, image classification, projections, simulation of dynamic processes (hydrology, landscape development) and terrain analysis. The functionality can be accessed through a GUI, the command line or by using the C++ API.
Contents
Running
To run SAGA GIS on the Live DVD, open the Desktop GIS group on the Desktop and click on the SAGA link.
When opening SAGA for the first time, you are presented with 3 subwindows: the Manager, the object Properties and the Messages window. The information in the object properties window will change depending on your selection in the Manager window.
You can close any of the windows (Manager, Object Properties, Data Sources and Messages). Try closing one of the windows to get more place for your map. You can show closed windows again in the **Window** menu.
Opening data
Open the SAGA GUI and load the grid `/home/user/data/saga/DGM_30m_Mt.St.Helens_SRTM.grd` via the **File|Grid|Load** menu.
You will get a message in the General tab of the Messages window regarding the success or failure of this task. You should see something like `Load Grid: DGM_30m_Mt.St.Helens_SRTM.grd...okay`. Once you loaded the dataset, it will show up in the Data tab of the Workspace window. It will be listed under Grids and the grid system it belongs to.
In this case, the grid system information will look like **30;312x 458y; 557970x 5108130y**. The first number is the cell size (30 meters), the next two numbers show the number of cells in x and y direction respectively, and the last two numbers are the origin of the grid.
SAGA's grid systems are referenced by the bottom left corner. This, and some more useful information on the dataset show up if you select the Description tab of the Properties window. Once you click on the tab, you will see not only more detailed information on the grid system, but also the Value Type of the grid (here FLOAT), the Value Range, some statistical measures and the Memory Size.
You can also load data by dragging and dropping it on the application. Try this with one of the datasets in the **/home/user/data/gdal_natural_earth/** folder.
Displaying data
To display the dataset in a map view:
Double click on the dataset in the Data tab of the Workspace window. A new Map window will open up with the dataset displayed. The canvas is framed: top and left the x- and y-world coordinates are displayed. Bottom and right you see rulers in map units.
Try moving the mouse pointer over the map and watch the x-, y- and z-coordinates displayed in the bottom bar of the SAGA GUI window. The z-coordinates displayed correspond to the elevation values of the dataset (be aware that the values displayed are always those of the dataset selected in the Data or Maps tab).
Now use the navigation tools to zoom and pan. The Zoom tool is selected by default. A left click on the map zooms in, a right click zooms out. Holding the left mouse button down, dragging to the opposite corner and letting the mouse button up allows you to zoom to an area of interest.
If you zoom in a lot and turn on Show cell values on Settings tab, you will see that the cell values are getting displayed. To pan, select the Pan tool and click and drag to move the map. Have a look at the other buttons in the tool bar: these allow you to zoom e.g. to Full Extent.
Saga zooms very fast, if you are lost while browsing your data, click the 'Zoom to Full Extent' button in the toolbar
Creating a shaded relief map view
We will enhance the map display by calculating a shaded relief map.
Switch to the Tools tab of the Manager window and click on the triangle left to the **Terrain Analysis - Lighting, Visibility** module library: the list with the modules of this library will show up.
Now select the Analytical Hillshading module and then select the Settings tab of the Properties window. This will show up the module parameters (also have a look at the Description tab, which will display more information about the module and its parameters).
Click in the right column of the Grid system parameter (where [not set] is displayed) and select the grid system of the Mt. St. Helens dataset (**30; 312x 458y; 557970x 5108130y**).

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String updated in the repository

  1. OSGeoLive
  2. saga_quickstart
  3. English
You will get a message in the General tab of the Messages window regarding the success or failure of this task. You should see something like `Load Grid: DGM_30m_Mt.St.Helens_SRTM.grd...okay`. Once you loaded the dataset, it will show up in the Data tab of the Workspace window. It will be listed under Grids and the grid system it belongs to.
You will get a message in the General tab of the Messages window regarding the success or failure of this task. You should see something like `Load Grid: DGM_30m_Mt.St.Helens_SRTM.grd...okay`. Once you loaded the dataset, it will show up in the Data tab of the Workspace window. It will be listed under Grids and the grid system it belongs to.
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read-only
Source string location
../../build/doc/quickstart/saga_quickstart.rst:59
String age
a year ago
Last updated
a year ago
Source string age
a year ago
Translation file
locale/pot/quickstart/saga_quickstart.pot, string 10