Especially since, to calculate current location, it needs an input of initial location (i.e. it needs GPS coordinates to begin with so it can track direction and velocity relative to that initial position). You can’t replace something you depend upon.
maniacal_gaff@lemmy.world 2 weeks ago
Even a perfect sensor will accumulate errors in the nav solution over time because there’s no such thing as a perfect gravity model. No free-running INS will ever replace GPS long term. This shit is so frustrating to see in the press.
fartsparkles@sh.itjust.works 2 weeks ago
eager_eagle@lemmy.world 2 weeks ago
the initial location doesn’t need to be GPS, just a known anchor location. Which is trivial to implement in the case of trains, since stations don’t move that drastically.
catloaf@lemm.ee 2 weeks ago
“Fixed” ground points move a surprising amount. The local ground can shift, and of course whole continents are constantly drifting.
eager_eagle@lemmy.world 2 weeks ago
surely these are things that should be considered, but they move in relation to what? And is this surprising amount of any significance for tens or hundreds of miles of rail?
hoshikarakitaridia@lemmy.world 2 weeks ago
But wouldn’t you scramble the precision with that? Stations can be quite big and anchoring to the station location means you already start with an offset to your location.
Depending on the accuracy over time, they could pinpoint a location while the user is sleeping and than use that as an anchor for the day.
But everything about that is speculative; let’s see where this goes first.
eager_eagle@lemmy.world 2 weeks ago
you’re thinking anywhere on the platform, I’m suggesting a known place near a station by which the train passes and its location - at that moment - is known.
All the system needs is a ground-truth location after a certain amount of time. GPS is just a cheap and convenient way to do it almost anywhere, but this location correction doesn’t need to be satellite-based.
Darkassassin07@lemmy.ca 2 weeks ago
It will definitely require corrections from GPS or other systems, but if made sufficiently accurate; it could be months or even years before the accumulated errors necessitate a correction.
What seems more concerning to me is a system like this would require 100% up time between outside corrections.
A gps receiver can acquire its position from a completely powered off state. Inertial guidence though, needs to be told its current position; then it can keep track of where it goes from there. If there’s any hiccup with power, you’ve completely lost your location fix and can’t reacquire it alone.
Put the two together though, and the inertial guidence can accurately fill in the gaps between gps service while also getting regular updates/corrections when you do have that signal available.
maniacal_gaff@lemmy.world 2 weeks ago
I don’t think you’ll ever see an INS going months without needing a correction. Imperfect gravitational compensation applies directly to the specific force measurements and those errors are then accumulated twice.