In QGIS the default projection, or CRS, is WGS84 Geographic Coordinate System. This CRS has become a global standard for latitude and longitude positions, such as those captured with GPS devices. Note that 'unprojected' data, or those with projections that cannot be interpreted will be projected by default in WGS-84 when using QGIS. It is possible to load layers with different CRS into a QGIS project and view them seamlessly in the same coordinate space. This exercise will introduce the basics of managing CRS in QGIS. See also Peter H. Dana's Map Projection Overview . In QGIS the default projection, or CRS, is WGS84 Geographic Coordinate System. This CRS has become a global standard for latitude and longitude positions, such as those captured with GPS devices. Note that 'unprojected' data, or those with projections that cannot be interpreted will be projected by default in WGS-84 when using QGIS. It is possible to load layers with different CRS into a QGIS project and view them seamlessly in the same coordinate space. This exercise will introduce the basics of managing CRS in QGIS. See also Next is a proj4 text panel, where projections can be set by pasting in proj4 format CRS statements. [You can look up proj4 statements by EPSG number at The Search by CRS Name panel provides a drop-down selection of the main Projection Authorities, such as EPSG, and a form to search for a name or ID number within that authority list. Close the Layer Properties window and note that the PROJECT CRS is also set to EPSG:4326 on the lower right of the status bar That is why all the layers are shown correctly, even though we have UNCHECKED the setting for ENABLE ON-THE-FLY CRS TRANSFORMATIONS ! Very often when adding incompatible CRS layers in the same map view, and with the ON-THE-FLY Transformation unchecked, the Map View will be blank QGIS 2.0 will automatically RESET the ON-THE-FLY Transform option, and your layers should now show up in correct relative positions Typically this means that the Project CRS will have been set to the active layer, which will look proportionally correct, while the other data layers will be so tiny that they will be visible as a single dot, or not shown on the screen at all The Map View will attempt to view all the layers, but in this example, the Egypt layers will be very distorted, because the WGS-84 CRS is not appropriate to be transformed to the China CRS Note, in the Project CRS listed in the STATUS BAR it is set to EPSG:2333 (which is a specialized Gauss Kruger Xian 1980 projection for China) The Map View should now seem more or less as we would expect it to, with the layers for Egypt, China, and Spain showing up in their relative positions. That is one advantage of using the Global Geographic CRS, WGS-84, because it should work for a map containing elements from anywhere on the standard global grid, and not be a custom projection that will only work for a specific area of the world. Most Projected Coordinate Systems are meant for specific areas or purposes. WGS84 was meant to provide a global framework for geodata, and is therefore a reasonable default setting for CRS. Source.


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Last Modified: January 26, 2015 @ 12:00 am