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pan mietek
Joined: 01 Jul 2008
Posts: 104
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 Posted: Tue Jun 26, 2012 3:03 pm Post subject: reliable values at low speed (what is in the "spd" |
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hi everyone
As I mentioned in the topic question, what speed is in the spd?
Is it speed calculated by the gps module and just displayed in the trekbuddy interface or is it speed calculated by trekbuddy using other data as time and position change?
pm
Last edited by pan mietek on Wed Jun 27, 2012 7:39 am; edited 1 time in total |
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Ranger
Joined: 12 Dec 2006
Posts: 4727
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pan mietek
Joined: 01 Jul 2008
Posts: 104
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| Posted: Wed Jun 27, 2012 7:49 am Post subject: |
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thx Ranger,
I've changed the topic as my goal is to get reliable speed values at the low speed range (c.a. 2-12 km/h)
If -as you've mentioned - "spd" variable gets its value directly from the GPS module i'd like to correct it to get more reliable readings.
My idea is to get average speed based on last 5 seconds to use it with running and walking.
Firstly my concept was to calculate it in hecl using time and distance, but maybe it'll be enough to make 5 seconds average of "spod" value?
What do you think?
pm |
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Ranger
Joined: 12 Dec 2006
Posts: 4727
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| Posted: Wed Jun 27, 2012 9:27 am Post subject: |
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Averaging ? I don't think so, cause low speed from receiver can be more reliable or not, depending on device used.
Second one - distance change with speed 2km/h means move around 0,55m per sec, 3km/h - 0,83m, 12km/h - 3,3m, etc.
Do you really get so reliable position data from typical consumer receiver, on typical data access level ?  |
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pan mietek
Joined: 01 Jul 2008
Posts: 104
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| Posted: Wed Jun 27, 2012 10:47 am Post subject: |
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right
so, let's say 10-15 sec avg?
Looking on logged tracks of running with stable 9-10km/h speed one can observe pretty regular ups and downs of speed curve.
Last 10-15 sec. averaging would aproximate it pretty good (as for running purposes).
Question is - should this averaging base on modules speed value (spd) or rather it should be calculated based on distance/time (as Bas mentioned i polish section)?
pm |
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Ranger
Joined: 12 Dec 2006
Posts: 4727
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| Posted: Wed Jun 27, 2012 11:27 am Post subject: |
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Both cases are device specific
If ie receiver gives you constant 0 speed value up to 5km/h, averaging just do nothing.
Counting speed from position changes means, that you need detailed info about position changes, sometimes in cm. Is it system so precise for consumer usage ?
I just don't think, that precise, current low speed value is so important in real navigation, rather for statistics
Logs can be post-processed outside app, and so on. |
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