Road alignment and angles
In line with our Revised Waze Editing Philosophy, our mapping standards have changed in 2020. For more information, see new technology, new mapping standards.
Segment positions need to be aligned with reality as closely as possible, typically to the centre of the road. To do this:
- Determine whether the satellite imagery in the area is trustworthy by comparing it with the GPS points layer.
- If the satellite imagery is trustworthy, align the segments to the geometric centre of the roadway using the satellite imagery.
- If the satellite imagery is not trustworthy, align the segments to the geometric centre of the tracks in the GPS points layer as closely as possible.
But first, what's geometric centre refer to?
On two-way segments, the geometric centre will not always be the same as the roadway centre line that splits the two directions of traffic. The geometric centre of the roadway will temporarily shift near intersections and exits where lanes are added, or where physical or painted traffic islands change the shape of the road. The snapper intelligence is smart enough to understand that roads widen closer to intersections, so in these cases, pretend the extra lanes are not there, avoid abrupt changes and keep the road straight and smooth. Some visual examples to help you understand are included below.
Determine trustworthiness of satellite imagery
You should determine the trustworthiness any time you are adjusting geometry to save yourself or another editor double handling the work.
First, turn on the GPS points layer (shift+G) and turn off the road layer (shift+R) in WME.
If the bulk of the arrows on the GPS points layer line up well with the roads on satellite imagery (some outliers are okay), it is trustworthy, and you should use it as the basis for roadway alignment.
But if the arrows show a lot of traffic that is not aligned with roads visible in satellite imagery, you cannot continue to rely on the satellite imagery.
See the following examples of trustworthy images and their captions below. You can click on the images to enlarge them.
In cases where imagery is trustworthy, align segments with the satellite imagery as close to the geometric centre of the road as practical. The lane lines on multi-lane roads may assist you in finding the centre of the road.
Imagery is not trustworthy if it is either misaligned or out of date. See the following examples and their captions below. You can click on the images to enlarge them.
If the imagery is not trustworthy, segments should be aligned with GPS tracks:
Bridges and overpasses
Even in areas with otherwise-trustworthy imagery, high-rise bridges and overpasses may be significantly misaligned. This is due to a phenomenon known as parallax.
Because the satellite’s camera is not always directly above the places it’s photographing, anything not at ground level might not be aligned. Where this error occurs, use satellite imagery to align segments at ground level, but follow the GPS tracks as you near the peak of the bridge or overpass.