Georeferencing Topo Sheets and Scanned Maps — QGIS Tutorials and Tips

Most GIS projects require georeferencing some raster data. Georeferencing is the process of assigning real-world coordinates to each pixel of the raster. Many times these coordinates are obtained by doing field surveys - collecting coordinates with a GPS device for few easily identifiable features in the image or map. In some cases, where you are looking to digitize scanned maps, you can obtain the coordinates from the markings on the map image itself. Using these sample coordinates or GCPs ( Ground Control Points ), the image is warped and made to fit within the chosen coordinate system. In this tutorial I will discuss the concepts, strategies and tools within QGIS to achieve a high accuracy georeferencing. Hipkiss’s Scanned Old Maps website has an excellent collection out-of-copyright scanned maps that one can use for research. 1.Georeferencing in QGIS is done via the ‘Georeferencer GDAL’ plugin. This is a core plugin - meaning it is already part of your QGIS installation. You just need to enable it. Go to Plugins ‣ Manage and Install Plugins and enable the Georeferencer GDAL plugin in the Installed tab. See Using Plugins for more details on how to work with plugins. Source.


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Last Modified: April 18, 2016 @ 9:01 am