Comment by closedcontour | Hacker News Reader

Comment by closedcontour | Hacker News Reader

Parent Full thread

Yeah, unfortunately this comes with the territory, especially with this Garmin inReach data. We are running in "expedition mode" which gives us updates about every five minutes but still, you will occasionally get badly spurious points. This is in contrast to the GPS track data you see in the activity viewer. That is collected from their watches which tend to not be quite as bad (although they have their issues too).

They are now on a narrow, somewhat technical ridgeline, so a few things will accumulate into some annoying errors:

  - the quality of the digital elevation model (DEM) isn't great in the Sierra Nevada (new data is slated to be captured this year, though!)
  - the overheard imagery is okay (0.6m), but not amazing
  - they will likely be hopping from side to side on the ridge, blocking sky view and making GPS quality decrease and frequency of updates decrease

All of this combines into what you see now: jumpiness, not registering with the ridgeline, and the summit points (where they are manually indicating they are on top) not lining up with the labeled points.

I hadn't even considered the DEM error. I can totally see it now that you've pointed it out though. The data is impressive either way.

I've had luck in the past with simply averaging the positions from multiple receivers, since horizontal multipath error on its own is typically under a couple tens of meters and it's so hyperlocalized that multiple receivers can experience totally different conditions.

On an unrelated note, do you know if they plan to continue with the half palisade traverse after they complete the rest of the crest?

Assuming everything goes to plan[1] for Nathan's list finish:

Today, Wed, July 6: A five-peak, north-to-south traverse of the southern Palisades: Palisade Crest, Norman Clyde, Middle Palisade, Disappointment, and Thumb.

Tomorrow, Thurs, July 7: A seven-peak south-to-north traverse of the northern Palisades: Temple Crag, Gayley, Sill, North Palisade, Thunderbolt, Winchell, and Agassiz.

[1] - https://www.sps2022.com/post/nathan-finish-plans

That's one hell of an itinerary.

The Garmin devices that they're using have built in GNSS receivers. There's no practical way to average the positions from multiple receivers for real-time tracking updates. Once the climb is finished, though, someone could download the recorded tracks from multiple devices and average them together.

Reply on news.ycombinator.com