Locations of visitors to this page

HOW TO DRAW ROUNDABOUTS




This article is on how to correctly draw roundabouts for Garmin auto routing GPS maps ©


When the correct roundabout polylines are used in Garmin maps, the GPS unit will give correct instructions such as

"...Enter roundabout and take second exit to Queen Victoria Drive..."


  • Remember key point is to draw polyline in correct direction of traffic flow !

  • Draw clockwise direction for traffic in UK, Thailand, Malaysia etc or

  • Counter clockwise direction for traffic in USA, Laos, Vietnam etc

  • After drawing polyline, make sure that one way box is ticked on both Properties and Routing tab.

  • Select "Roundabout" in Properties tab and also under Routing tab (which is actually called Collector/Roundabout)

  • Must draw this in two sections - ie must not be a single circular polyline as auto routing does not allow polyline to self intersect!

  • Remember to connect nodes when finished.

  • When drawing in roundabouts - need to be careful not to place too many nodes closer than 5.4m otherwise it may cause problems in compiling - easy method to overcome this is to make the roundabout slightly larger.

  • One extra node between two intersections is usually enough for small to medium sized roundabouts (eg. total of 8 nodes in a roundabout with 4 streets should suffice.

  • If drawing in some one way lanes with triangular dividers, I use 12 nodes to maintain a circular shape.

  • I have found out that including too many nodes on the roundabout causes the compilation process to arbitrarily generalise the nodes and actually sometimes <>severely distorting the shape of the roundabout!)

  • I also set all my roundabouts at 20kph speed limit (could use 40kph at larger ones) as realistically most of the time this is about the speed of traffic going round a busy roundabout. I am trying to aiming for auto routing on the maps to be able to estimate a more accurate time to destination.

  • Here is an example of a roundabout template I use...

  • Roundabout (clockwise) drawn for left hand side traffic flow

    • eg. UK, Malaysia, Australia, NZ etc

    • NOT USA, Europe, Vietnam, Laos etc


  • Ignore labeling of roundabout, not necessary to do so.

  • Click diagram for larger display





    GO BACK TO MAP AUTHORING ARTICLES




    GO TO MAIN ARTICLES PAGE




Advertisements


HOME

Site Counter

DONATE to RCMAPS