Forum: General Topics
Forums / General Topics / Minor "simplify track" problem report
| Subject: | Minor "simplify track" problem report | |
shchenka 18:00 | I've been often using the "simplify track" function to reduce the number of points in track. In fact I've been using it recursively with a success, as it would always converge to a number of points where the algorithm could not "simplify" the track any further. Very useful (and in fact I wondered why you had not engaged such recursion as a default behaviour). But recently (a couple of times but only today) it would just remove almost all the points from the track, reducing it to a useless zig-zag. "Number of track points reduced from 1815 to 43 points" seems a bit too optimistic ;-) Only reporting. I'll see if this happens in the future again. | |
Stephen 18:36 Location: Phone Model: | Its been a while since I wrote the Simplify Track code, but from what I remember you *may* get this weird effect if the track has a very long section of widely spaced points (eg, motorway driving with a large 'min distance' setting) followed by a short section of dense points (eg walking with a small 'min distance'). The Simplify algorithm initially removes points that are a lot closer together than the track average, so you might find the dense points get trimmed a bit harshly, though 1815 to 43 does seem rather extreme, as you say!! (This slightly erratic behaviour is why it isn't used by default!) | |
shchenka 18:47 | That might be, since I'm now alternating between "driving" and "geocaching" profiles as mentioned in another thread, and both produce very different track patterns (I set my "geocaching" mode to be *very* dense). | |
Stephen 19:16 Location: Phone Model: | I should probably alter the code to treat each section independently, which should prevent the effect you've been seeing (assuming that the driving and geocaching parts were separated into different sections). Might not have this ready for the next version though... | |
shchenka 20:47 | I'll try to investigate this a little more and will share any conclusions. I did not start new section manually, and I tend to jump out of the car rather quickly, so I don't expect a new section would initiate due to inactivity. | |
shchenka 16:08 | Today I had 1830 reduced down to 415, then 415 to 286 and down to 267 and 262, so it reduced a lot, especially in the first shot, but it still makes sense. The "high density" parts have been almost completely deleted. I've forgottent to start new sections when changing the activity profile, though. I'll see next time. | |
shchenka 7:12 | Yesterday's track reduced from 3600 down to around 600, again mixed driving-walking, so this is pretty consistent. The "dense parts" of the track get almost wiped out. | |
Stephen 13:52 Location: Phone Model: | I'm planning to completely rewrite the simplify track code to make it more reliable and also to allow a 'simplication amount' value to be specified. Might have it ready for the next version, but we'll see (I'm hoping to have the next version ready by the end of the week)... Cheers, Stephen | |
shchenka 15:16 | Of course, I don't consider this a major problem, although I've learn to use the feature a lot (it helps to speed up startup e.g in a case of a crash). I forgot to mention that this time I've tried to start a new section each time I'd changed from the dense to the sparse mode or vice-versa. | |
ChrisM 15:56 Location: Phone Model: | If it doesn't do so already, wouldn't it make sense to automatically create a new track section when changing the profile (say from Driving to GeoCaching)? I think this would be what you want more often than not, and you could always use the option to combine the track section if necessary. Maybe it could be another option; 'Create New Section When Changing Profile (y/n)' ...? What do others think? Chris. | |
Stephen 11:22 Location: Phone Model: | Could be useful in principle, though it might be a bit fiddly to implement - currently when you change profile in the main Activity Profile menu or shortcut menu it instantly changes between the profiles, so if you were just changing from, say, Walking to Driving, it would switch to Cycling in between, which would then generate an extra unwanted track section. I guess I could make it wait a few seconds before creating the new section, more for it to 'think' about though! | |
ChrisM 11:36 Location: Phone Model: | If it's tricky, don't worry about it on my behalf! Maybe it would be easier to choose the profile you require, then activate it (say by pressing the 'fire' button) ?? Chris. | |
shchenka 20:02 | Or if there was a way to avoid cycling between the profiles ... | |
shchenka 8:14 | I just wanted to report that the problem seems to have gone with 0.6.3 but you don't mention it in the realase changes announcement, so maybe I'm just lucky. Or I'm only deluding myself :-) Cheers. | |
Stephen 9:33 Location: Phone Model: | Good point, yes the new version does have a completely new Simplify Track algorithm. I forgot that I'd changed this - also I didn't completely finish testing it, so let me know if it does anything odd. It now uses the Minimum Track Distance setting from the current profile to determine how much detail should remain in the simplified track. The higher this distance, the more aggressive the simplification. I might add a new menu option to control this so that its not directly linked to the profile, but will see how it goes... | |
shchenka 8:18 | I'm happy with it depending on the profile. Knowing that gives the user somecontrol over how aggressively it behaves. Thanks. | |
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