Presets for activities?

Gammalerik · September 21, 2011, 09:59:52

This post is not so much a feature wish, but more of a question. Could it be wise to have presets for your chosen activity when starting a new track recording? The arguments here are accuracy versus battery consumption.

When driving a car you need the intervals between points to be very low to be able to record sharp turns accurately. I guess 1 sec is appropriate. Perhaps 4-5 seconds when bicycling. Running could be 7 seconds. Walking perhaps 10 seconds. At sea in a kayak or canoe, one tend to paddle in a straight line quite slowly. 60 seconds will do then. Just suggestions. The crucial bit here is to have the presets as low as possible so people do not feel their track is inaccurate. Also, the more activities to choose from the better so people can find their thing. Suggested activities:

Car trip (motorcycle)
Road bike (racing)
Mountain bike/commuting
Running
Walking
Hiking (more twists and turns than regular walking on a road)
Kayak/Canoe
Custom (Manual track intervals input)

Now it also depends on if the points recorded really DO add to battery consumption? Anyway, having these presets will eliminate some of the fiddling with options in settings, which for some people are a lot of. Me personally like 100s of settings, but it can sometimes be forgotten to tweak the interval before I start an activity.

There is no need to actually remove the "meter" and "second" interval setting from options, they can still serve as an override of the preset activity.

Khaytsus · September 21, 2011, 17:08:07

I've seen a few apps in the past that will analyze the data and if things are moving fairly consistantly in a straightish line, point records will go slower, but if you're accelerating or turning, the points will increase. Now this pretty much assumes a location is being taken every 1-2 seconds or so for this to have accuracy in turns, just the data is not recorded if not necessary. So in terms of actually gathering data, it probably doesn't help, but it does reduce unnecessary track points.

But the real reason I'm responding is to suggest if you need to record tracks often, I suggest you get a bluetooth GPS. It'll greatly reduce battery consumption vs the internal GPS, it's more accurate, more sensitive, and you could even opt for one that has a built-in track logger and not use the phone at all to do it! Of course for live tracks, or a 'record in, follow out" type of scenario you'd want a the phone to record it.

Personally for all of my tracking I have a Columbus V900 that has a built-in track log and I record everywhere I go and then the data is analyzed (per the first paragraph) based on some parameters (I have a default, or I can specify walk, bike, car, low, all, etc..) and it's imported into a database that I can view in a web browser against Google Maps, or live export from KML into Google Earth etc.. It's kinda neat if I'm curious the last or times I was at a location, going to that spot in Google Earth then turning on my "all time" KML and seeing points. I have to click etc to see 'em, so it's not perfect, but several times has quickly answered 'when was I here last?" type questions. I keep saying I'm going to write some code to summarize that for me, but never get around to it

Gammalerik · September 22, 2011, 10:55:34

By the way which of the two settings governs? Interval in meters or intervals in seconds?

Gammalerik · September 22, 2011, 13:32:37

Up till now I have recorded tracks in more or less constant speeds. Today I jumped on my racing bicycle to test these variables with a combo of 15 meters intervals (minimum distance between recorded points) and 5 secs intervals. I found out that the time interval is the only thing that is taken into account when recording. When reaching a top speed of 43km/h (12m/s) there was as much as 75m between recorded ponits. Regardless of the 15m interval I had specified in settings.

Am a bit confused now

PS, maybe this thread belongs in "discussion" section

Menion · September 22, 2011, 13:38:12

don't be

both values are used in same time and ONLY IF BOTH met criteria, point is stored. So only if time since last point is bigger then 15 and also when time since last is bigger then 5s, point is stored

.. pretty simple ..

supermaz · September 23, 2011, 13:07:51

Ouch, I thought it would be an OR criteria. Record if the last point is 5s or 5m away. Wouldn't this make more sense?

For the unnecessary points I use prune on the exported GPX files which has functions to automatically reduce the number of points without loosing accuracy.

svartbjorn · September 23, 2011, 21:23:24

Quote from: "supermaz"Ouch, I thought it would be an OR criteria. Record if the last point is 5s or 5m away. Wouldn't this make more sense?

I disagree. I find the current definition to make sense - and exactly what you want and what you need. You want to specify a min time internal to reduce the number of stored points, and you know from your activity which interval makes sense. At the same time there is no reason to store a new point of you haven't moved. And the definition of moving is the up to you by setting the min distance interval. So as Menions is saying - these are AND conditions, and that makes absolutely sense to me. I use them all the time.

A couple of hints:
- if you want the stored information of a track to show both moving time and total time, you need to set min distance = 0m. This is because Locus uses the stored points to calculate this information.
- because of the inaccuracy of GPS position, setting min distance = 0m will cause your track to show a lot of small movements in all direction while standing still. This will also add some meters to you total distance. This is particularly a problem if you set "Time between GPS locations" > 10 seconds or so, since the GPS receiver will wicth off as soon as the position is found. The accuracy won't be as good as when the receiver is on all the time and constantly works on maximum accuracy. Setting min distance > 20m (depends upon the satellite coverage) will reduce or eliminate those small movements.

Bottom line: Locus has a very strong set of configurations here - "Time between GPS locations", "Interval in meters" and "Interval in seconds" - that allow the user to tune accuracy, stored track size and battery usage (setting "Time between GPS locations" > 30s reduces battery drain significantly) to his/her specific need for each trip. I have not seen such a strong feature set in any other GPS program.

durian · September 23, 2011, 21:41:33

I think supermaz has a point as well. Imagine you have an activity with variable speed, and you set 5 meter/5 seconds. If going slowly, you probably get one point per 5 seconds, so far so good. But when speed is increasing, the 5 meters will be covered in less than 5 seconds, so you want a point each time that happens too, to keep the smoothness/accuracy of the track.

Actually, even better would be an algorithm which sees that you are changing direction, and than store more points. When going in the same direction, less points can be stored. But that takes maybe to much CPU power.

-peter