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Bardia Region Overview - Image processing - Part 8  This exercise is divided into eight parts and requires the use of LEOWorks. Digitalisation In our digital classification, many small river streams are missing, because of their size and also because of the season. The image was taken in February, at a time when these river streams carry a very small amount of water. We can create a digitalised network of missing river streams and merge it with the classified image. Digitalisation is a useful and common method used to merge pixel and vector data. This could be the drainage system. In the following exercises, we will digitalise the river networks from the 'Bardia_landsat_2002_band_453.tif' and merge it with the supervised classification image 'Bardia_2002_maximlike.tif'. Open the 'Bardia_landsat_2002_band_453.tif' image and click on the GIS button. A pop-up menu will open. Choose File>New Theme, name the theme 'River' and select Polyline. To start digitalisation, select Edit> start Edit. Digitise the rivers and streams which are missing in supervised classification. If you make a mistake, just do one or more left clicks to delete the last vertexes. Once you have finished the digitisation, choose Edit>Stop Edit to stop digitalisation. Select Edit>Properties and set the colour and thickness of the vectors. Save the theme 'River' to your folder 'Bardia'. Open the image 'Bardia_2002_maximlike.tif'. Choose GIS and Open Theme River.shp, specify 'Arbitrary' and 'Map based', and then set the colour and thickness options with Edit>Properties.
1. Assess the accuracy of the digitised rivers.
If you find mistakes within the system, choose Edit>Start Edit and Edit>Edit Vertex or Move and correct the error(s). Then save the shape file again. You will do more exercises on change detection and GIS.
Last update: 16 April 2013
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