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At which point do I stop uploading traces for some region/route? For example, I could upload two GPS traces every day for trip to work, but those roads already have lots and lots of the traces. From the mapping perspective, there is no additional benefit from new traces, unless road configuration changes. On the other hand, there might be some uses of huge trace database, for example, average travel speed calculations. So at which point do I stop uploading traces for some roads? |
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Upload as much as you can. Even though there may already be lots of traces for a single road, the traces may be put to new uses in the future, exactly as you suggest. The only caveat is that if you always start or end from a significant place such as your home or place of work it would be possible for someone else to identify these places. 1
About new uses in the future: You also have to remember that some people might edit their traces, so you never know whether e.g. speeds are real.
(11 Jul '10, 19:21)
driver2
Most (almost all?) of the edits are to trim off the ends to hide the start and/or the end of the journey, so the remaining detail remains intact.
(11 Jul '10, 19:49)
ChrisH
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I don't know about that, Chris. I edit traces and move all trackpoints to be one second apart in 1970. Which would really stuff up the speed calculations!
(27 Oct '10, 01:22)
samwilson
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More GPS traces help to minimize the GPS error. However when averaging traces be sure to check the final result from some other source (i.e. aerial imagery, place survey). Fix the road location is important thing to do, but there probably are more applications, like measuring average speed on the road (as you said). |
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I recommend not to upload traces you know that are erroneous. For example you know a place where due to reflections the GPS track is always off. Also areas where the GPS receiver was not moved and is recording random GPS-clouds should IMHO not be uploaded for not hiding actual GPS tracks. I don't feel we have the absolute need to have a hundred traces covering the same road. But a few more than a single one make it a lot easier to be confident about the actual geometry of highways. Especially those areas that don't have high resolution aerial imagery available can benefit from different tracks for the same highway. |
