7.3.1. Setting a coordinate system and saving the new QGIS project (*.qgs)
Similar to the ArcGIS section (6.3.1.), it is important and recommended to first set the coordinate system according to the data used for the analysis or the target projection of the final map product, respectively (Fig. 72):
- Go to Settings.
- Select Project Properties.
- Select Coordinate Reference Systems (CRS).
- Activate the checkbox on top called Enable “on-the-fly” CRS transformation.
- Select the projection called CH1903 / LV03 with the EPSG-code 21781 within the list of the Coordinate reference systems of the world (Group Swiss. Obl. Mercator, see Fig. 72) with a double-click.
- Click OK to apply these settings and close the Project Properties dialog.
- Verify by checking if the EPSG-code 21781 is written in the Status Bar
(see Fig. 68).
Note: This step is very important for the rest of this tutorial, because choosing the wrong CRS may lead to various problems in geoprocessing.
Advanced users who deal with a variety of different projections might appreciate the possibility to filter the list of all coordinate systems (Fig. 72) by names or the identification number of the EPSG Geodetic Parameter Dataset (http://www.epsg-registry.org). Switching back to the General tab of the Project Properties, the Layer units will be now set to meters, because the Swiss oblique Mercator projection uses metric units.
- Save the new project and settings, go to File.
- Select Save Project As, or click the button to the desired destination folder (A QGIS project file with the extension *.qgs will then be created).
- It can be reopened directly by a double-click on the file or within the QGIS main menu File > Open Project or the open project button from the File toolbar.
Fig. 72. The Coordinate Reference System (CRS) of the project has to be defined within the Project Properties. In the same dialog the on-the-fly CRS transformation can be enabled or disabled.