Electronics > Projects, Designs, and Technical Stuff
Are accurate clocks really the limiting factor in cheap Inertial Navigation?
RoGeorge:
If you have a precise clock and are allowed to look at the stars to recalibrate, than it's possible to find out the precise location. It was a huge prize for a precise enough clock (or other method to navigate in the open sea, without following the shore line). Many methods were presented. One of them was looking at the star and precisely knowing the time, except there were no accurate enough clocks back then.
Very long but interesting documentary/dramatization:
In theory, an extremely precise clock can be used for inertial navigation (without reference stars). In practice, it won't be easy to beat the GPS.
CatalinaWOW:
Clocks were a huge problem a couple of hundred years ago. Not so much today. The magnitude of the time error in celestial observation is roughly the rotation rate of the earth surface in the celestial reference times the time error. More or less 500 meters per second of error. For a garden variety quartz wristwatches that means about 250 meters of position error per day since last setting of the clock. For high precision wristwatches that becomes something more on the order of 500 meters per month. Go to a commercial Rubidium standard and you cut those errors by another couple orders of magnitude.
For an accelerometer to contribute the same 250 meters per day as the garden variety wristwatch it has to have offsets and gain errors on the order of 3E-08 g. Such accelerometers are not garden variety. Similar story for rate sensors.
For those who like laser ring gyros look up Sagnac effect.
magic:
--- Quote ---exciting research by our colleagues on quantum gyroscopes should make this thing even better, but the first bottleneck at this point is to make a portable high accurate clock.
--- End quote ---
I read it: there might be some super duper technology in the future which certainly wouldn't be possible without our invention and although it may still not happen with our invention if it does happen it will totally be some awesome stuff. And we gotta invent some impressive sounding justification for our research to make beancounters happy.
Mechatrommer:
--- Quote from: Doctorandus_P on March 25, 2019, 05:08:45 pm ---Inertial navigation was accurate enough to hit London from the west coast of the Netherlands in WW2.
The amount of drift you can expect of "modern" sensors is related to price you pay for them.
--- End quote ---
true only if path is near straight line or nice parabolic as errors dont accumulate that much. retry with zig zag motion, the rocket may end up in seabed or top mountain desert, if not on civilians occupied area. as mentioned, even the most expensive spaceship will need correction based on landmark or beacon/gps. if this idea is correct, people should have already proved the concept with special vehicle setup with Cesium clock on board. the portable atomic clock maybe just a dream or another 21st century buzz. but then an "atomic gyroscope" maybe something else.
--- Quote from: Doctorandus_P on March 25, 2019, 05:08:45 pm ---One way you could copensate for drift in road traffic is to map the accumulated data to the road map, ans assume you can only travel over the roads.
If you accumulate enough left and right turns you could even get the location from that even without prior knoledge about the starting position.
--- End quote ---
it may work as this is not purely dead reckoning. a simple AI, or path alignment can be embedded as driver can still see the road. pure dead reckoning may end up vehicle turning into grass field, not with a human driver.
StillTrying:
It seems strange that a University of Sussex dept. the Prof. and phys.org don't realize that a lot more than a miniature atomic clock is needed for the none-GPS ambulance or mobile phone navigation, but we all do!
Debunked. :)
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version