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star guide digital astrolab

instead of triangulatoin with gps, a digital camera of the stars to provide you a location
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a digital camera that does the work of the old compass/map and astrolab and solar tracker combined with a watch...... to provide the best possible position fix and heading.

of course, this won't work in cloudy weather, but-----it will be robust to not depending on a gps system.

gps systems only work at certain latitudes, glonas and european gps work at more northerly lattitudes. but when you look at the globe------------civilian location tracking is rather limited.

teslaberry, Apr 23 2014

GPS performance standard http://www.gps.gov/...rmance-standard.pdf
2008 version [lurch, Apr 24 2014]

Well, somebody had to do it.. fake_20astronomical...d_20to_20navigation
[not_morrison_rm, Apr 25 2014]

cart that always points...in some direction http://en.wikipedia...th-pointing_chariot
[not_morrison_rm, Apr 25 2014]

[link]






       Delightfully retro.
normzone, Apr 23 2014
  

       Have you been following innocentive.com? There was a contest requesting ideas like this.
bungston, Apr 23 2014
  

       Shouldn't be too hard to bake. I know there are systems that can do this on military aircraft for example but an app would be nice too.
DIYMatt, Apr 23 2014
  

       The position of planets should allow the app to automatically figure out roughly what year and month it is (based on predicted positions for the next several hundred years), then based on the position of the moon, the day (and if is accurate enough), the time as well. That way when you loose track of the time you can still navigate.   

       Of course that does make it orders of magnitude more complicated than an app that can pattern match one constellation in each hemisphere and take an acceleropmeter reading angle.   

       Practical matters: what's the typical accuracy of cell phone accelerometers for measuring angle? If the accuracy is 1 degree, then your navigation can be accurate to about 70 miles.   

       How hard is it for a cell phone camera to take photos of stars? I think you might need a tripod and a long exposure time. I seem to remember it being somewhat tricky, even with a good quality camera.
scad mientist, Apr 23 2014
  

       //How hard is it for a cell phone camera to take photos of stars?//   

       Harder than it is to phone someone up and ask them where you are.   

       //gps systems only work at certain latitudes// What evidence is there for that?
MaxwellBuchanan, Apr 23 2014
  

       //but when you look at the globe------------civilian location tracking is rather limited.//   

       I didn't even notice this the first time I read the idea, but this is totally wrong. Civilians GPS navigation is accurate down to centimeters where WAAS is available and down to less than a meter over the entire world.
DIYMatt, Apr 24 2014
  

       what evidence is ther for gps availability?   

       do you even know how triangulation works? and range and angles? gps for civilians is severely limited.   

       as for calling someone on a phone? UM NO ---you are NOT USING any connectivity to establish location.   

       also, the military , darpa have already developed chips for dead reckoning of location, that are probably more accurate than this system, but that technology is pretty far advanced using special hardware. the solution i'm suggesting probably doesn't need any sophisticated hardware.....   

       buchanan for someone who knows a bunch about space----gps is something you should know about. you should know the major players, glonass russia european systems, us dod gps
teslaberry, Apr 24 2014
  

       //gps for civilians is severely limited.// do YOU know anything about the GPS system? you seem to think this is still 1992 when civilian access was limited. My iphone will be able to find my position down to the meter literally anywhere on earth, as long as I have a clear view of the sky. I still bunned this idea because I think celestial navigation with my phone would be cool, and a good backup for the rare occasions when GPS satellites break.
DIYMatt, Apr 24 2014
  

       //what evidence is ther[e] for gps availability?//   

       Well, that would probably be from the US Department of Defense's Global Positioning System (GPS) Standard Positioning Service (SPS) Performance standard <linked>.   

       In particular, on page 19, the coverage standard per satellite is given as 100% coverage of the globe (usable signal assumed to require 5 degrees elevation above the local horizon, coverage to the full globe less local blockages), and on the next page, coverage standard per constellation is given as 100% coverage of the globe.   

       In other words, every satellite participates in providing coverage to every part of the Earth, and as a whole, every part of the Earth receives adequate coverage from satellites to provide positioning at all times. That's the operational standard the US DOD sets for the GPS system.   

       OK, you say they don't provide that standard of service. Prove it.   

       (Degradation of GPS triangulation capability at high latitudes is not from lack of coverage. It comes from two sources - 1) Increased VDOP (vertical dilution of position) because there are no satellites near the local zenith for the solution, and 2) the GPS receiver itself may not adequately correct for the change in signal refraction in the shallower ionosphere nearer the poles. This is a highly speculative source of error - most commercial gps units model ionospheric refraction quite well.)
lurch, Apr 24 2014
  

       //an acceleropmeter reading// I think this is a more sophisticated type of sensor that compensates for little jiggles in a handheld device?
pocmloc, Apr 24 2014
  

       //Harder than it is to phone someone up and ask them where you are.//   

       Max. Where am I?
AusCan531, Apr 24 2014
  

       [AusCan531] - let's start with the basics.
Where's the last place you remember being?
Where are you supposed to be?
Do you recognize anything you see?
Are you drunk?
Do you have your clothes on?
  

       I'm not sure I got those in the right order...
lurch, Apr 25 2014
  

       Hmm, I'm guessing that as a plan B, you could have an app with an accelerometer that does the "cart your you pull along that always points home" thingy linky.   

       //this won't work in cloudy weather,   

       There goes the UK sales. Hmm, gives me an idea. See linkette.
not_morrison_rm, Apr 25 2014
  

       I have been thinking about the error in an accelerometer. I wonder if one could correct for this 1: correlatively or 2:iteratively.   

       For example: the app takes 1000 pictures of the sky. Predicted location is compared to GPS location. If there is a consistent and nonrandom directional error in the accelerometer, build in a fudge factor. Whenever GPS is available, use that to calibrate the accelerometer / astrolab prediction.   

       Suppose the error is random. Several thousand measurements should converge around the correct location.
bungston, Apr 25 2014
  

       Taking this further, it could be implemented as a fake. You open the app, it quietly finds your location from GPS, then photograps the sky, then looks up what it ought to find, then draws lines connecting the stars it thinks it can see and then announces "based on the stars I can see I think you are here". Should convince 99% of punters. Many users would still believe in it even if you used it on an overcast day.
pocmloc, Apr 25 2014
  

       If you're going to fake it, might as well fake a Viking sunstone.
lurch, Apr 26 2014
  

       We got up to astrobabe on the other topic, it's probably a bad sign.   

       Nobody signs up Sandra Bullock, debris magnet...
not_morrison_rm, Apr 26 2014
  

       /sunstone/   

       I love it, lurch! My submission to the Innocentive contest was a device similar to that proposed here, but incorporating a polarised lens to serve as a sunstone.
bungston, Apr 26 2014
  

       I would like someone to weigh in on the concept of iteration to control for random error because of imprecise measurements.   

       /Practical matters: what's the typical accuracy of cell phone accelerometers for measuring angle? If the accuracy is 1 degree, then your navigation can be accurate to about 70 miles./   

       Could one improve on this by taking multiple readings?
bungston, Apr 26 2014
  
      
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