This exercise continues to use the dataset from exercise 1. You can download this from
here.
This exercise will classify the elevation model to show are
1) Ensure that GB OST50 UK CLIP is open in the map window.
2) Navigate to Statistics. Note the minimum and maximum height values in the details pane on the right hand side. Based on the details decide upon some suitable height intervals to use for the classification for example height intervals of 200m.
3) Navigate to Raster > Raster Operations > Classify.
4) Under Classify Options choose a cold to hot (blue to red) style from the Derive Class Colours From drop down.
5) Select the Intervals button, select Method and choose Interval Spacing.
6) Set the Value to 200 and click OK. Now you can manually adjust the intervals or round up numbers, if you have selected Output Type as classified you will be able to enter your own Class name instead of the default Class 0, Class 1, Class 2 etc.
7) Navigate to the Output File Explorer and and name the file UK Classified Elevation.
8) Click Process, you will see the task pain open and sow progress. Once finished the new classified grid should appear in the map window.
The new grid paints a very different picture to the original grid, it is clear to see that there are a few very high areas in the UK as opposed to original map that made the terrain look more equal in elevation.
Note: Although this output may not be visually appealing, it does precisely visulise the highest elevations in the UK. In many cases when raster data is used for analytics the aim will be to identify particular areas or hotspots in a dataset. Classifications and colour stretches are key to identifying areas of interest.
This exercise contains OS data © Crown copyright and database right 2016. OS OpenData is free to use under the Open Government Licence (OGL). OS Terrain 50 user guide and technical specifications can be found here.------------------------------
Chris Jenkins
Pitney Bowes Software Ltd
Henley-on-Thames
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