Edge 305: How to increase accuracy of the elevation record

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Edge 305: How to increase accuracy of the elevation record

Postby CHnuschti » Sat Jul 25, 2009 6:29 am

Garmin Edge 305: How to increase accuracy of the elevation / climb record // Elevation jump bug. (Original thread)

Pointing this out once "FYI".
In older firmware, when you hit the start button (to begin the record) of the Garmin Edge 305, you could experience a sudden jump in the (absolute) elevation. Since firmware v2.80, this jump in elevation has been partly corrected. The jump in elevation when hitting start still happens, but now jumps back to the elevation displayed just before you hit the start button.

Now for a good accuracy of your elevation climb record it is essential to have the correct elevation at start. If at start let's say the elevation has an error of 50m, it usually takes more than 30min until the elevation continously converges to the correct value. A known issue, see this pic (red is digital map, blue is the edge record); seen relative, the record of the elevation is correct, however wrong in the absolute value:
Image

To have the elevation as accurate as possible (AND not having wrong climbs/descents) at start of the record you have to follow these points:

- Get out and switch the unit on, wait until it has aquired satellites. Once aquired, change screen so you can see the elevation. Now don't move, do not hit the start button and WAIT, till the elevations climbs/drops to the correct value. From my experience I can tell that in 9 of 10 cases it takes only 1-2min until the elevation has reached the correct value. You can follow on the screen, how the elevation climbs/drops to the right value.

- Once it has the correct value, hit start. Now you will see a jump in the elevation occours (in most cases). This happens within 1-2sec, a jump forth and back. Now the point is, while you still have the correct elevation, this jump (in most cases) has already been recorded, so if say it jumped 100m, you alredy have a ascent/descend of +/-100m. To avoid this record, stop the record, then reset the record (press reset for 3secs). Finally hit start again, the jump will NOT occour again, and start your ride.
Check this pic out of Sporttracks of the described jump. This record lasts only 5sec, but the jump is recorded, and gives a climb/descend of +/-134m !
Image
This jump also shows up when imported into Training Center (TC). However, climb/descend shows up as 0m, so maybe it is filtered out (in the record lasting only 5secs; if this jump is integrated in a hole ride, i don't know what the behaviour of TC is). Not so clear. But imported in Sporttracks, as said, this climb is accounted for, and in the raw record it's there in any case. A point that BTW IMO could easily be fixed in the firmware by excluding the record ot the jump.

- Third point is, use "smart record" in your settings. If you use "1 second record", there might be some problems with the elevation / climb record, see this post.

regards

Additional note: Some Edge 305 users did not confirm this elevation jump, this issues is possibly depending from what device ("age") you are using.
Also it's unknown/unconfirmed so far if this happens in newer devices such as the Edge 705.
CHnuschti
 
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