by Amith ES
Are you one among those thousands mappers out there literally scratching and banging your head to effectively draw a roundabout owing to your not-so-good drawing skills? If yes, then read on.
Well, I assure that you’ll be able to do effectively draw a roundabout once you finish reading this tutorial.
This tutorial will explain a procedure for using an overlay image to provide a circular path upon which you can trace the path of the roundabout, resulting in a nice-looking, perfect circular road.
Firstly start looking around for an unmarked or not-so-perfect roundabout. Done with finding an unmarked roundabout? Great, I say.
Here is an example of an un-mapped roundabout:
1. First, select a transparent circular image to be used as an overlay, on which you will "trace" the path of the roundabout. For instance, the image attached below would do the trick. The image is also located here: http://i.imgur.com/GytlT.png
2. In MapMaker, select "Overlays" > "Manage overlays". If the Overlay button is not displayed at the top right corner of the Map Maker window, enable it in MapMaker Labs. Click the gear icon in the upper right corner and click Labs. Select Enable for the Overlays lab.
3. Add the URL to the circle image in the Image field, and click Add. The image will be added to the MapMaker window. Click OK to close the overlay source window.
4. Google Map Maker does not currently import images with the correct aspect ratio, so your circle image will likely be drawn as an oval. Using the handles on the corners and center of the image, resize and position the circle over the physical roundabout as shown in the following images.
5. Once the overlay image is properly sized and positioned, you may begin drawing the road to create the roundabout, tracing along the overlaid circle.
NOTE: You cannot draw a roundabout in a single operation. You will have to draw two semicircles. When drawing the semicircles, try to leave the endpoints where the roads coming into the roundabout will intersect the roundabout itself, so as to avoid creating unnecessary intersections. See the example below. Half of the roundabout has been drawn, with the endpoints of that first segment positioned at the points where the not-yet-drawn green roads will intersect the roundabout.
The video tutorial embedded below gives you a fair idea on drawing a roundabout with perfect geometry. Please note that basically I was drawing the roundabout over an already marked roundabout. That’s the reason why I could not show the entire process in the video.
#1. Always uni-directional (One way).
#2.Roads within the round-about should have the segment usage as 'Roundabout/traffic circle'.
#3.The roads within roundabout should be given the priority of the highest among the connecting roads.
#4.Speed and number of lanes to be given suitably.