Generalise river network

• RivEX can simplify a river network by reducing each polyline to a straight line.  You may want to do this when displaying continental scale river networks.

• A copy of the network is created and the polylines are generalised.  A new field is added to the attribute table called StraightLn and this is the length of the straight line.

• All other attributes are copied to the new file. No nodes are removed which means the topology of the network is unaltered by this process.

• Select your network, polyline ID, From and To node fields and press Build to construct the data dictionaries.

Whilst the data dictionaries are not used during the generalisation process they do provide a useful validation of the network.

• The slider bar does not alter any parameters, it simply changes the image for you to appreciate the output of generalisation.

• Select the generalise tab and press Go!, the output of this process is written to the C:\RivEX\Output folder using the naming convention of adding "_generalised" to the layer name.  For example, if your network is called worldrivers then the filename of the generalised data will be called worldrivers_generalised.

• In the image below, the network to the left is generalised into the image on the right.

• Each polyline is reduced to a straight line between the original From and To nodes.  Be aware that intersecting polylines can be generated as shown by the yellow line in the image below.

• RivEX will generate metadata for the above process which you can read in ArcCatalog.  Remember the style sheet filters what you see, so you will need to swap between different style sheets to see specific information generated by RivEX.