New Page - Tunnels

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Re: New Page - Tunnels

Postby CBenson » Fri Feb 21, 2014 5:39 pm

sketch wrote:And I assume anything that does have valid GPS points for the whole time won't trigger that particular merger function.

That would makes sense, but I'm not quite as optimistic.
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Re: New Page - Tunnels

Postby harling » Wed Nov 21, 2012 7:43 am

martinchaney wrote:There needs to be some way of marking segments as tunnels so Waze knows not to expect GPS reception in them. As it is, Waze is generating automated map errors because it thinks people are getting more directly from point A to point B and thinks there's a missing road.

My introduction to the IGN editors was the addition of a freeway segment connecting two ends of a tunnel in a straight line, intersecting and junctioned with a couple ramps and service roads along the way. They obviously saw the GPS track and concluded that there must be a new bridge there...
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Re: New Page - Tunnels

Postby harling » Mon Feb 24, 2014 10:12 pm

Please forgive my late re-entry into this discussion.

The main thing that distinguishes tunnels from other segments is the lack of GPS data--and the problem we are trying to solve is not how to detect tunnels or designate them on a map, but how to route through them when faced with that lack of GPS data. (In fact, if equipment were installed in certain tunnels that provided both accurate GPS information and data service, they wouldn't require any special handling at all.) A guideline of applying a negative elevation to a tunnel segment is harmless--as long as the routing engine doesn't start making assumptions based on it.

As I have mentioned ad nauseum, there are sections of the Central Artery in Boston where underground ramps crossing both above and below the main tunnels, all directly below both street-level and elevated roads. It's a perilous area to edit, and any one-size-fits-all rule about relative elevation is almost guaranteed to fail at some point. [I am not aware of any place where we have run out of negative elevations and need to assign a non-negative elevation to an underground segment, but it could happen. I am certain that we have had to use a -5 in more than one location.]

As for the more important problem of navigation, I'm still convinced that the only manageable way to navigate a network of branching tunnels (in which GPS and/or network connectivity are unavailable) is to treat the entire "dark" graph of segments as a black box with M inputs and N outputs, and each of the (MxN) combinations has its own total length and transit time. The segments are visible to the driver, editors and routing engine for the sake of calculating distance, displaying the map, generating turn instructions and (maybe) generating the "black box" data structure itself, but any attempt to treat each internal segment between points A and B independently, as is done above-ground, will be a combinatorial nightmare.
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Re: New Page - Tunnels

Postby harling » Tue Feb 25, 2014 4:42 am

kentsmith9 wrote:
harling wrote:Please forgive my late re-entry into this discussion.
The main thing that distinguishes tunnels...

Lots of good thoughts in there, but I am not sure I saw a suggestion to change in our current page. :mrgreen:

Frankly, the time of championing my own ideas regarding Waze (e.g., reviving the Best Practices page) ended a couple years ago. I have plenty of ideas, and read many good ideas from other people, but in my experience all the talk in the world has resulted in very little actual implementation. If anything I post is noteworthy today, I'll leave it to someone else to include it wherever it belongs, and not bother writing functional specs and such until I'm on the payroll.
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Re: New Page - Tunnels

Postby jemay » Mon Oct 29, 2012 4:15 pm

What about any discussion about the Landmark - Tunnel? Should that be added or help in identifying the tunnel?
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New Page - Tunnels

Postby kentsmith9 » Sun Oct 28, 2012 11:34 pm

From my searches of the Wiki I do not find anything that covers more of the "theory of operation" around tunnels. WeeeZer14 mentioned to me that it comes up enough it would be good to have something to reference. Currently on our Map Editing Page we have a TODO item on Tunnels. It is listed as "How to add tunnels", but currently nonexistent. We can link that to this page and cover any aspect of the tunnel.

I propose a full page with the following basic information. Below is the basic content/outline. Any comments or suggestions are welcome. Once we get far enough along we can create the actual "Tunnel" Wiki markup and add the appropriate interpage Wikilinks. I need feedback on the Theory of Operation section since I am making that up based on what I know about the segment tracking.

Also I rarely go though any tunnels, but I have one just north of me (mostly straight) that I can do some basic tests as needed. If someone has more experience with tunnels please speak up.

I did find a few threads talking about tunnels and sound like the problem is worse than I have described. My description appears to be the solution after the Waze client app uses the accelerometer in the phone. Is it possible some phones provide more tracking in tunnels than others? If we don't know I can pose the question to the Waze team to try to get an answer.
http://world.waze.com/forum/viewtopic.p ... 51#p197951
viewtopic.php?f=16&t=22589&p=250978&hilit=tunnels#p250978


-------------------------------------------------
PAGE: Tunnels

Tunnels are no different from any roadway segment(s) including bridges, viaducts, overpasses, etc. The are drawn and modified the same way as any other road using the geometry nodes to shape the roadway through the tunnel.

==Theory of operation==
The complication with navigation through tunnels is that generally they obscure GPS communication and cell phone data connections. The Waze servers track each mobile device (driver) as they enter and exit each segment along their route. With the start and end times of each segment, the Waze server can calculate the average speed of drivers through that segment. This is how the Waze server can determine if the tunnel traffic is flowing normally, or if there is a slowdown of the vehicles in the tunnel even without the GPS tracking information while inside the tunnel.

<!--
1. Is this correct? Again the few times I have passed through my short tunnels I did not pay attention.
2. Do we want to get into more details than this?
3. What does it do if there is a junction inside the tunnel and only the outside ends of both segments are accessible to the server. Does it simply take a weighted average based on proportional length of the two segments and assign average speed to both based on the one reading?
-->

==Creating a tunnel==
Due to the GPS and mobile device data communication problems inside tunnels, the mapping process of the tunnel is difficult if it does not follow a straight path from the entrance to the exit. The important point of any tunnel mapping is to at least connect the two entrances to enable the routing engine to use the roadway through the tunnel as appropriate for destinations on the other side of the tunnel.

Find on the visual map the locations of the two entrances of the tunnel. If you know the tunnel is a straight path through the tunnel you can simply draw a new straight road between the two entrances and name the segment appropriately. If you don't know the path of the tunnel personally, check to see what is shown with the GPS tracks through that area. If it shows a consistent path of curves, then the active mobile devices are able to track and communicate the data back to the Waze server and you should lay out the road following that path by altering the geometry nodes to match it.

If you know the roadway is curved by personal experience and there are no matching curved GPS tracks, consider estimating about where the curves exist inside and shape the segment using the geometry nodes. Then once that new roadway segment is live on the client app you can drive through that tunnel and if the mobile device has the ability to generate its own internal GPS estimate you can see about where on the map your vehicle is in relation to the roadway. Note where the road may turn before or after the map display and make adjustments when you return to the map editor later. Although it is not critical that it match exactly, it is helpful for drivers to have the visual route be similar to the real road as they pass through the area.

==Junctions in tunnels==
Some roadways through tunnels include splits or exits to other routes inside the tunnel. Creating the split is done the same as with any other junction. As described in the section above, the GPS tracking and navigation may make it difficult to know exactly where in the tunnel that turn truly exists. In the case of splits and exits, it is more important to be more accurate in the estimate of the actual roadway split or exit so the navigation directions match the roadway as closely as possible.

==Tolls for tunnels==
If a tunnel requires a toll to be paid in order to pass through the tunnel, use the same toll road controls as for any other roadway segment.
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Re: New Page - Tunnels

Postby kentsmith9 » Tue Oct 30, 2012 4:38 am

Sure enough. I forgot to add that to my post. Thanks for the reminder.
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Re: New Page - Tunnels

Postby kentsmith9 » Wed Feb 19, 2014 6:00 am

I was thinking about moving ahead with this current proposal (I had since forgotten about it). I am bumping this one in case anyone missed it the first time around.
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Re: New Page - Tunnels

Postby kentsmith9 » Thu Feb 20, 2014 2:26 am

sketch wrote:Should we add a rule that all tunnels shall be set to negative elevations? All to -3 (unless tunnels cross underwater)?

edit Just found this: https://www.waze.com/forum/viewtopic.php?f=212&t=64030

CBenson and I were just talking about this. My response and proposal:
Kentsmith9 to CBenson wrote:If I recall they were using that logic in an upcoming feature for Tunnel recognition, but there was no functionality related to it yet. I would just leave it out of the Wiki, or possibly put it on the talk page of Tunnels after it is built.


sketch wrote:Should we add text explaining that Street View can be used to determine a curved tunnel's geometry, the location of ramps, etc.?

Great idea. I had not considered this, but as long as the inside of the tunnel is recorded by Google Street view we are golden. Also I just played around with this is Berkeley and Street View will show you were on the visual map you are in relation to the Street View bubble. As you step forward in the street view the bubble on the Visual map shows you the current location underground. I can now map the road to the bubble as I step through the tunnel.

Or do we already know the GPS location of the street view is not that accurate and this is all for not? :(
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Re: New Page - Tunnels

Postby kentsmith9 » Fri Feb 21, 2014 4:54 pm

sketch wrote:I would imagine whatever Street View says is better than nothing, and nothing is exactly what we have for GPS data in tunnels. I use it sometimes to help in New Orleans, where big old trees can make some roads basically impossible to see from the air.

Nice. Had not considered that one either. Frankly I had no idea the street view was forcing the icon to the correct GPS location. I think there may be other things we can get from that. I think we should add that tip to nanoRep and the Best Practice pages.

sketch wrote:Regarding the elevation, I'm basically thinking "why not?" It certainly makes sense to have tunnels at a low but not railroad-low elevation—well; underwater tunnels, anyway, rather than tunnels through mountains and all.

I think the "why not" is because tunnels are not always below other roads when in the mountains as you mentioned. Current guidelines say to use relative elevation, but we have 0 saying "ground" in the editor. So mountain tunnels could be negative only if you consider there is ground above them. I suppose if the road entering the tunnel were elevated at +1 being on supports, the tunnel section could be -1 with no problem.

But before we go through all this, shouldn't we understand what Waze back end does with this information? If they assume a tunnel when below "ground" elevation, what is happening to our underpasses we have below ground?
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