CREATING AUTO ROUTING MAPS - EXTERNAL NODES

How to create External Nodes

To be able to auto route from one map tile to another map tile within the SAME MAPSET, all routeable polylines (roads and highways) that exits or enters separate map tiles must be "defined" as an external node.

Therefore, roads and highways that are meant to join must not overlap each other across map tiles.

This is depicted as a large BLUE DIAMOND on GPSMapedit.

To do this.

Go to the last polyline node at the edge of the map tile.
Use Node tool (M)
Right click - NODE PROPERTIES
Click on Routing Tab
Tick the box "Is external node"
Click "OK"
That's it !

"Click on the screenshot to enlarge"

The tricky part is to make sure that these "External Nodes" are aligned EXACTLY to the nodes on the adjoining map tile!

The coordinates MUST be exactly the same on both map tiles.

Open the other map tile where the roads will be connected to.
I find it easier to open a second GPSMapedit session.
Go to the road which joins up with the road in the first map tile.
Perform the same steps as shown above - to tick box "Is external node"
Check alignment of coordinates by clicking "Position" tab.
Ensure that Latitude and Longitude matches exactly with those on the other map.
If they don't match, auto routing will FAIL !
Just copy and paste one set into another to synchronise both sets of coordinates.
That's all !

"Click on the screenshot to enlarge"
Do the same for all the other polylines at map edges.

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