I have a potentially useful and fairly large collection of tracks in Kenya, because I regularly drive and fly there and record all my movements. I would like to upload these tracks, but have one question first:

Does OSM detect and avoid unusable parts of these tracks, preferably automatically?

The unusable parts I can think of are:

  • Flight tracks. They could be recognized by the persistently high speed, by the lack of any sharp turns, and by the fact that nobody else ever moves near or parallel to any considerable part of any such track.
  • Game drive tracks. They are actually useful, but even after they have been used for many years, they can become disused and disappear over the course of a few years. The most useful ones could be recognized by having been used multiple times over the course of more than one year. However, OSM would need a mechanism to remove them after they have not been used at all in something like 5 recent years.
  • Tracks into private property. I don't switch off the tracking when I enter a private ranch, for example. This cannot be recognized automatically. I guess though that the resulting mapping is OK, particularly when it is a dead-end road anyway. We do map roads in large private compounds, right?
  • Off-road driving. I guess this should not be mapped. Such tracks can be recognized by not being used multiple times over the course of more than one year, so it is possible to detect and ignore them automatically.

A related question is the recognition of the quality of the road. The only method I can think of is to map classes of roads depending on speed. Since it is always possible to drive more slowly than possible and since the GPS may occasionally jump, I think the extremes should be ignored and the middle speed range should be used. The median is surely a better indicator than the average. Of course a road should never be mapped from just one track. The absolute minimum in my opinion is two similar tracks that are very close to each other and ideally at least several months apart.

But the general question remains: Does OSM have the means to do automatic track preprocessing of this kind at all? If not, perhaps it would be better if I did not upload my mixed tracks.

I know that Tracks4Africa has such software, but I cannot deal with them, because they do not communicate properly. I think though that automatic mapping from tracks is the only method to get useful maps for upcountry Africa and other developing countries, because there simply are not enough people there who have the time and the money to do manual mapping. I certainly will never find the time to turn my tracks through large areas of upcountry Kenya into a perfect map.

In some areas even GPS tracks will be scarce or nonexistent, so it is important to make the very best use of what is available. Please consider that even a mediocre map of a road, made from a few tracks, is infinitely better than not having that road in any map at all.

asked 28 Aug '11, 07:16

hgmichna's gravatar image

hgmichna
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Your question is much more complex than can effectively be handled in this Q&A system. help.openstreetmap.org is aimed at finding the "single best response" to a clear question; you should really post your question on the talk mailing list or the forum for a broader discussion.

Having said that, tracks are just the groundwork upon which a map can be built. Building the map is usually a manual process. Your assumption that "automatic mapping from tracks is the only method to get useful maps for upcountry Africa and other developing countries" is a common fallacy; the same reasoning is used by some people to argue that we have to import third-party areas because "there will never be somebody to do all this work". The problem with that is that a body of data in itself is close to worthless; we also need the community to maintain the data. Without the community, we might as well not import (or auto-generate) the data in the first place.

That's why we don't do automatic track-to-map conversion.

The answer to your question is: Yes, do upload the tracks, and where possible and where time permits, manually make a map from them; even if you don't have the time, your tracks might be useful to somebody else who e.g. combines them with aerial imagery to get an idea of the situation on the ground even if he lacks the first-hand knowledge that you have.

But as I said, your question has several interesting aspects that go beyond the simple structure of a question-and-answer system. Do join the mailing list.

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answered 28 Aug '11, 08:30

Frederik%20Ramm's gravatar image

Frederik Ramm ♦
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accept rate: 24%

edited 28 Aug '11, 08:34

First of all tracks are not the only thing you need to make a map. You also need the type of road and other information. Without this it can be hard to create a map. However your traces might be good to have for other people when they have misaligned satelite images or working from local knowledge. This is how Haiti was mapped and the few traces that was uploaded to OSM was used to align the satelite images.

There is no simple way of identifying what type of trace you have or average out several traces. The easiest way is to manualy trace over the gps traces like OSM is currently doing. OSM can do a lot of manual work because of the great comunity that are willing to do this. It is not about a few people with a lot of time and equipment making a map, but all of the people with little equipment making a better map.

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answered 28 Aug '11, 07:42

Gnonthgol's gravatar image

Gnonthgol ♦
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accept rate: 16%

If you can add anything over your traces it would as you say help,as Kenya as little of the area mapped.There is some bing background but in the area I looked at only a large river could be identified but you could maybe with local knowledge plot a bit more.If you have any 50 year or older maps that will be out of copyright (I assume this is correct for Kenya? please say if you know otherwise) use them to identify what your traces are over. So I would say upload them as others on the ground could and I'm sure will eventually use them

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answered 28 Aug '11, 09:22

andy%20mackey's gravatar image

andy mackey
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accept rate: 4%

Thanks for the good explanations! I will try to select the most useful road tracks and upload them. If I ever get to it, I may try map-making, but after the already high effort to get the tracks, perhaps I can leave the map-making to somebody else with more experience.

If any map-maker is interested in central Kenya, please let me know. Perhaps we can form a two-person team. I can answer a lot of questions about certain roads and areas there.

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answered 28 Aug '11, 13:05

hgmichna's gravatar image

hgmichna
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accept rate: 0%

1

Do not fear to learn to edit the map. It is easy and quite rewarding.

(28 Aug '11, 21:40) Gnonthgol ♦

What you're suggesting could work - I'd drop a mail to one of the mailing lists (see http://wiki.openstreetmap.org/wiki/Mailing_lists). There's a "talk-africa" list, but it doesn't seem very active (http://lists.openstreetmap.org/pipermail/talk-africa/). Maybe trying the main talk list (http://lists.openstreetmap.org/listinfo/talk)?

(28 Aug '11, 21:49) SomeoneElse ♦
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question asked: 28 Aug '11, 07:16

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last updated: 28 Aug '11, 21:49

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