Author Topic: A navigation technology that does not rely on satellites.  (Read 1438 times)

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hamster_nz

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A navigation technology that does not rely on satellites.
« on: April 28, 2019, 04:38:39 am »
Location services without space vehicles and online tracking...

https://www.aweigh.io

A Raspberry Pi plus add-ons and python scripts that uses the position of the sun to tell you where you are.

I can't tell if they are trying to be serious, or it is an 'art piece' .

Poe's law is a b#%ch.
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hamster_nz

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Re: A navigation technology that does not rely on satellites.
« Reply #1 on: April 28, 2019, 04:43:56 am »
I watched the video, and now I deeply regret ever mentioning this!
Gaze not into the abyss, lest you become recognized as an abyss domain expert, and they expect you keep gazing into the damn thing.

hagster

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Re: A navigation technology that does not rely on satellites.
« Reply #2 on: April 28, 2019, 06:52:08 am »
TLDR;it could "work" if you only need position to the nearest country.

The "basics" page is worth a look.

https://www.aweigh.io/basics

I haven't looked in detail, but the premise sounds reasonable. Basically they are using the polarisation of scattered sunlight to try and determine the position of the sun. Then if you also know the time, you can calculate your location. This is basically what a sextant does.

I note that nowhere do they show the result. My guess would be that if they could make this work to within 5 to 10 degrees(lat or lon) they would be doing really well. There will be plenty of error in the polarisation measurement. An error of 1 degree would could equate to a error of 100km on the ground. And the angular diameter of the sun is about 0.5degrees to start with.

Lets not get started on the list of things that they say rely on sat positioning. Many actually use it to derive time. This project just uses a regular clock.

Domagoj T

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Re: A navigation technology that does not rely on satellites.
« Reply #3 on: April 28, 2019, 08:57:41 am »
It would also need an accurate compass and some very accurate maps of magnetic declination.
How would it be affected by various cloud formations? What about night time? What about reflected light that is depolarized? I don't see it nearly accurate enough to be usable.

techman-001

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Re: A navigation technology that does not rely on satellites.
« Reply #4 on: April 28, 2019, 11:15:52 am »
I watched the video, and now I deeply regret ever mentioning this!

Why ? this is a well known science in avian tracking:

"Unlike GPS devices, which are too large and heavy for the warblers, geolocators use miniaturized sensors to detect and record solar light-level data hundreds of times each day. These data are stored on a tiny computer chip and can be downloaded only if the birds are recaptured. Daily locations can then be inferred from calculations based on day length and the timing of solar noon and midnight."

https://vtecostudies.org/blog/the-blackpoll-warblers-daring-ocean-migration/

I have been a (small) part of such a project and results were impressive, but not GPS impressive.

hamster_nz

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Re: A navigation technology that does not rely on satellites.
« Reply #5 on: April 28, 2019, 11:09:00 pm »
I watched the video, and now I deeply regret ever mentioning this!

Why ? this is a well known science in avian tracking:

"Unlike GPS devices, which are too large and heavy for the warblers, geolocators use miniaturized sensors to detect and record solar light-level data hundreds of times each day. These data are stored on a tiny computer chip and can be downloaded only if the birds are recaptured. Daily locations can then be inferred from calculations based on day length and the timing of solar noon and midnight."

https://vtecostudies.org/blog/the-blackpoll-warblers-daring-ocean-migration/

I have been a (small) part of such a project and results were impressive, but not GPS impressive.

I can see that as working - maybe within a degree or two, and you can run a 'best fit' and smooth things out.

However, for Aweigh, there a python script (you can see at
https://github.com/build-aweigh/build-aweigh/blob/master/Software/RaspberryPi/Latitude_Longitude.py )

And it is buggy - the servo driving the polarising filter starts out OK with

Code: [Select]
p = GPIO.PWM(18, 50) #Frequency is 50Hz
p.start(5) #Duty cycle is 5 to turn 60 degrees

Code: [Select]
while time.time() < t_end:

.... code to take reading ...
# Turn motor 60 degrees
p.ChangeDutyCycle(7.5)
time.sleep(1)
... code to take reading ...

... calculation ...

At no time do they reset the filter back to the original orientation for subsequent passes.

But the web site and video is pretty slick.

All they need is "micro-blowers" and they are ready for a Kickstarter
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0culus

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Re: A navigation technology that does not rely on satellites.
« Reply #6 on: April 29, 2019, 04:42:09 am »
Bring back LORAN-C

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techman-001

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Re: A navigation technology that does not rely on satellites.
« Reply #7 on: April 29, 2019, 05:41:02 am »
Light level Geo-location is a well known alternative to GPS as mentioned in followups, here is a video showing Kirtland’s warbler migration tracks by Nathan Cooper of the Smithsonian Migratory Bird Center.

These use tiny geolocator tags with a battery life of years due to low power mcu usage, no GPS and the RTC being the only fully powered perepheral.

borjam

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Re: A navigation technology that does not rely on satellites.
« Reply #8 on: April 29, 2019, 01:18:55 pm »
Indeed, those techniques are commonly used to track migrating birds.

How could you put a tracking device on a barn swallow otherwise?

JacobPilsen

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Re: A navigation technology that does not rely on satellites.
« Reply #9 on: April 29, 2019, 05:24:47 pm »
There is an older Czechoslovak television series "Visitors - Expedition Adam 84", where the central supercomputer blindly relies on positioning anything derived from his own position, but (after decades of service) stands outside the spirit level...
youtu.be/b-wwgN-KbpI?t=1350

imo

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Re: A navigation technology that does not rely on satellites.
« Reply #10 on: April 30, 2019, 06:16:59 pm »

rrinker

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Re: A navigation technology that does not rely on satellites.
« Reply #11 on: April 30, 2019, 09:02:08 pm »
Indeed, those techniques are commonly used to track migrating birds.

How could you put a tracking device on a barn swallow otherwise?

Well two of them could carry it between them on a line....

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hamster_nz

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Re: A navigation technology that does not rely on satellites.
« Reply #12 on: April 30, 2019, 09:24:46 pm »
Light Level Geolocator:

Nice project - but confirms that the resolution is to about a degree (which is cool for some uses, but not for finding your way to your secret spy meet-up)

Quote
LLG has error of, say 100km versus 10m for GPS, ie. four orders of magnitude worse accuracy. On the other hand, commonly available GPS units have consumption in order of tens miliwatts, while LLG can track and log its position with consumption of microwatts, that is four orders of magnitude less.
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Canis Dirus Leidy

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Re: A navigation technology that does not rely on satellites.
« Reply #13 on: May 01, 2019, 11:17:15 am »
A Raspberry Pi plus add-ons and python scripts that uses the position of the sun to tell you where you are.
I can't tell if they are trying to be serious, or it is an 'art piece' .
More looks like an unholy mix of ДАК-ДБ-5 and БЦ-63 a computerized toy versions of real life devices for celestial navigation, heavily filled with advertising.

Smf