Maximum Nerdage - GPS track + Google Earth

Supposedly the newer patch antennas are improved over the older eTrex's. I sometimes run mine in my pack top pocket, sometimes in the front pocket of my shell (so I can easily check my vertical footage quota ;)) It makes a little beep when it loses signal, but for the most part it does really well, and there were only a few errors for the day. I am actually surprised at how much you can smother it and it will keep receiving.

If you think this is geeky, last season I kept a spreadsheet of my days. Location, skis, conditions, notes, partners, and any stats I could derive from those basic values. What else is a fuggin egghead supposed to do when all he can think about is skiing, but is forced to code shit?

I'm gonna give that MotionBased Lite a whirl. I draw the line at paying though, no matter how cool it is. :nonono2:

Hey bio-smear...
I'm curious how much of an adjustment you see with the altitude calibrations performed by motionbased.

For instance, for a couple hours of skiing MB totaled 19K vert for me (which worked out when I thought about the lifts I rode and hikes I did); in contrast, my GPS recorded over 35K. There were not many "dips" (short ups & downs), so I know that was not the culprit -- I think it's the intra-day fluctuation of the barometric altimeter in the Garmin unit that is the cause.

I'm interested to know what their "calibrations" are. I have yet to play with it[MotionBased], but the only way they could be correcting recorded altitude is by 1) Omitting outlying recorded elevations that are obviously erroneous, like a spike that occurs in an extremely short time interval(huge huck?) or 2) compare the altimeter setting(the calibrated sea level pressure) from the nearest reporting station(like Reno/Tahoe Intl Automated Weather Observation) records. Sounds contrived to me.

Temperature can affect realtime altimeter readings too. The problem MB is trying address I think is the jockeying around of readings due to varying temp for a barometric altimeter(rare), or signal irregularity for GPS altimeter(less rare.)

After searching their forums, they seem to want to smooth their elevation data out and eliminate the irregular points. I dont care how dirty my data is(if it's dirty at all.) My irregularities might be me throwing a switch-cork-7-dong-slap-grab off the Cutthroat rock.

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Originally Posted by upallnight

I think it's the intra-day fluctuation of the barometric altimeter in the Garmin unit that is the cause.

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Originally Posted by bio-smear

Omitting outlying recorded elevations that are obviously erroneous, like a spike that occurs in an extremely short time interval(huge huck?) or 2) compare the altimeter setting(the calibrated sea level pressure) from the nearest reporting station(like Reno/Tahoe Intl Automated Weather Observation) records. Sounds contrived to me.

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WOW.....NERDS!!

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Originally Posted by bio-smear

After searching their forums, they seem to want to smooth their elevation data out and eliminate the irregular points. I dont care how dirty my data is(if it's dirty at all.) My irregularities might be me throwing a switch-cork-7-dong-slap-grab off the Cutthroat rock.

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Yeah, sort of. After using their service for several years -- and specifically recording over 60 ski days with it this year, I've started to see that their corrected data is much more accurate than what my Garmin unit reports.

The cool thing is that they give you the ability to turn the correction on and off, as you like.

I'm curious if you do some experiment...like track some runs on a lift of known elevation, and compare what you think you should have to what your GPS reports & what motionbased calculates.

They have spent alot of time figuring out the calibration, and they discovered that the Garmin devices (a) record plenty of bad data and (b) fail to throw the bad data out. Garmin acknowledged the problem (when the MB team reported it to them), but chose not to do anything about it with "older" devices.

Motionbased is now part of Garmin, actually.

MB is focused on tools for endurance athletes, but it's interesting stuff (to me) nonetheless.

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Originally Posted by upallnight

I've started to see that their corrected data is much more accurate than what my Garmin unit reports...
...what motionbased calculates.
They have spent alot of time figuring out the calibration...

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Upallnight-

Can you tell me what they're correcting exactly, other than eliminating bad points? It seems like without benchmark reference data, there is no way to correct a single altimeter reading, or determine if it is erroneous. I can see correcting summary data, like total vertical, by recalculating from the raw data, but I'm having a hard time understanding how they reject certain points. I'm sure they know what they're doing, I'm just having a hard time getting it.

The Vista C has an altitude calibration page where you can specify a known elevation, and it will calibrate all readings from that. I rarely do that though, and hadn't given much thought to the accuracy of my data. Important for instrument flying maybe, but for skiing I can accept some high tolerances.

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Originally Posted by Tin Woodsman

Awesome. But that topo is pretty broad brush. AAre there any software packages that approach/approximate a standard USGS 1:24,000 series?

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I used OziExplorer to overlay the track from a tour around Shuksan Arm at Mt. Baker onto a standard USGS map. Click the thumbnail to see a larger image.

http://img188.imageshack.us/img188/8...narm3lg.th.jpg

I gotta get me one 'a these.

Too bad Google Earth's resolution in the Alps is horrible, but still it's inspiring me to get a GPS. Why? What's the point of something like this? I dunno but it's somehow kinda cool!

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Originally Posted by bio-smear

Upallnight-

Can you tell me what they're correcting exactly, other than eliminating bad points? It seems like without benchmark reference data, there is no way to correct a single altimeter reading, or determine if it is erroneous. I can see correcting summary data, like total vertical, by recalculating from the raw data, but I'm having a hard time understanding how they reject certain points. I'm sure they know what they're doing, I'm just having a hard time getting it.

The Vista C has an altitude calibration page where you can specify a known elevation, and it will calibrate all readings from that. I rarely do that though, and hadn't given much thought to the accuracy of my data. Important for instrument flying maybe, but for skiing I can accept some high tolerances.

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I believe they're tossing out the data from the internal barometric altimeter and using the GPS elevation from their database. They are then tossing out the random GPS data points that do not seem to correspond to the rest of the activity.

For more detail, it's probably a question best asked in their forum. The developers will respond (if they haven't already written a thread on it).

I calibrate my altimeter reasonably frequently, but even if I do it once per day I have noticed that the vertical displayed on my device for the day can be up to 2x my actual vertical (in terms of distance I covered, whether on lifts or on foot).

YOUUUUUUUUUU FUCKINGGGGGGGGGGGGGGGGGGGGGGG NEEEEEEEEEEEEEEEEEEEEEEEEEEEEERDS!!

Pretty cool shit admittedly though :fmicon:

That's cool. I used a Vista all last summer to make maps of road rides around here last summer along with elevation profiles. I gotta get a PC, though - GPS geek stuff is hard to find for the Mac.

Has anyone tried the new Garmin Edge? Looks nice, and has rechargable batteries.

Does the fact that I know exactly what they're talking about, yet could never actually explain it to someone else make me a nerd as well? Maybe it's the closet nerd inside of me trying to escape......or maybe it's the "cool guy" in me trying to take over the nerd that I actually am.

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Originally Posted by tomw_n

YOUUUUUUUUUU FUCKINGGGGGGGGGGGGGGGGGGGGGGG NEEEEEEEEEEEEEEEEEEEEEEEEEEEEERDS!!

Pretty cool shit admittedly though :fmicon:

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We already have a nerd basher here by the name of Oger... although he has been Noticeably absent from this thread...

Are you gonna kick sand in our faces and then steal our bitches?

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Originally Posted by bbirtle

I gotta get me one 'a these.

Too bad Google Earth's resolution in the Alps is horrible, but still it's inspiring me to get a GPS. Why? What's the point of something like this? I dunno but it's somehow kinda cool!

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The height data's not bad though so the 3d stuff looks pwerty :)

edg