Homemade GPS Receiver

http://www.aholme.co.uk/GPS/Main.htm

by sly010 • 11 years ago

106 55 11 years ago

aholme.co.uk

Quanticles3• 11 years ago

If anyone is interested in GPS, we're looking for a software engineer ready to learn about it. (Full Time, Austin)

shubb• 11 years ago

Totally off topic but I'm seeing a lot of hiring going on in Texas. What is going on down there?

natebleker• 11 years ago

Tax incentives, lower cost of living, and pro business local governments are driving larger companies to relocate headquarters or major research ops to Texas en-mass.

Quanticles3• 11 years ago

It's a big tech hub outside of silicon valley that's arguably more fun and undeniably less expensive

Xeoncross• 11 years ago

Right after CA, Texas is the highest GDP state. It's also has beautiful clouds and sunsets.

teekert• 11 years ago

Google Fiber? (In Austin at least)

amyjess• 11 years ago

Texas has always had a huge tech industry presence, particularly the telecom industry: http://en.wikipedia.org/wiki/Telecom_Corridor (and there's also a lot of tech industry here outside the Corridor proper, too)

Personally, I love living and working in the suburbs of Dallas, and I wouldn't want to live anywhere else.

jhayward3• 11 years ago

The Texas economy has, until a few months ago, been booming due to shale oil & gas development. Add in no income tax and warm weather with young folks doing sporty things and it's fairly attractive.

Austin has a somewhat robust semiconductor focus, with Freescale, AMD, Intel, and Apple present. Some low-power IOT type tech including Silicon Labs (Energy Micro), and Ambiq in addition to afore-mentioned Freescale. There are a few DOD/spook type shops, and some financial techs, such as Visa, Paypal, Netspend, etc.

knodi123• 11 years ago

That sounds interesting, can you post more details? Experience, compensation, requirements, description, etc?

Quanticles3• 11 years ago

Isocline - Austin, TX - Software Engineer for High Performance Computing and Modeling

We are looking for two people - one interested in neural networks and one interested in GPS.

We are developing microchips that yield a 10-1000x improvement in performance & energy-efficiency compared to digital ASICs, GPUs, and FPGAs. We are a bootstrapped company and are fully funded through mid 2016. Patents pending.

C++ experience is required!

$70K – $150K Salary

0.5% – 1.2% Equity

Full Job Description: https://angel.co/isocline/jobs/38767-software-engineer

Company website: http://isoclineengineering.com/

jkot• 11 years ago

I would be bit careful. GPS is military technology and commercial versions must have limitations, to be non-usable in rockets (max speed, max altitude...).

tyho3• 11 years ago

Says the USA, thankfully the author is not based there. That being said, the USA does seem to think many of its laws apply all over the globe.

ape4• 11 years ago

He might want to visit the USA some time.

ceequof5• 11 years ago

Incorrect.

The relevant agreement is the Missile Technology Control Regime, an informal partnership between 34 countries. http://en.wikipedia.org/wiki/Missile_Technology_Control_Regi...

Unlocked GPS receivers are classified as dual-use missile-related components under category II, item 11, section A.3: http://www.mtcr.info/english/MTCR-April2011-Technical-Annex....

  b. Designed or modified for airborne applications and having any of the following: 
    1. Capable of providing navigation information at speeds in excess of 600 m/s; 
    2. Employing decryption, designed or modified for military or 
    governmental services, to gain access to GNSS secure signal/data; or
    3. Being specially designed to employ anti-jam features (e.g. null steering 
    antenna or electronically steerable antenna) to function in an 
    environment of active or passive countermeasures.

kiiski• 11 years ago

Aren't those limitations just in the USA? I'd guess that someone in .co.uk should be able to do what ever they want, especially as a non-commercial project.

toomuchtodo5• 11 years ago

Yes, but if you violate ITAR, you'd probably want to avoid transiting the US in the future. We're pretty militant about enforcing our laws beyond what you'd consider sovereign boundaries.

chisleu5• 11 years ago

Came for this. This allows someone to build GPS-guided missiles, artillery, etc.

The laws need to be changed, because consumer-programmable things like FPGAs and SBCs like BBB/RPi have made weaponizing with even commercially-available, off-the-shelf products super easy.

For instance, building gps-powered drones with thermite self destruct and an explosive/incendiary payload is fairly straight forward and extremely dangerous with little ability to investigate the violator. ICBMs and fast-flying missiles are much harder.

toomuchtodo5• 11 years ago

Don't even need FPGAs; you could do it all in software and use very light software defined radio hardware.

deutronium2• 11 years ago

I'm not sure how you think changing laws would protect anyone, anymore than they currently do?

Sure lots of things can be used for both good/evil.

Personally I think it's a fascinating project.

cnvogel2• 11 years ago

If 1000 lines of Verilog code (or a little bit of patching in a commercial receiver's firmware, for that matter) is the only thing missing from the terrorists having a working cruise missile, then we're screwed anyway...

Personally I'd love to see more of the advanced features (such as carrier phase measurements and also multiple antenna support) being available in affordable hardware. Preferably in an open system, being open source, providing schematic diagrams, having open APIs and allow access to raw measurement data.

krapht2• 11 years ago

Ublox LEA-6T + RTKLIB not enough?

mcculley• 11 years ago

Selective Availability was turned off in 2000 (15 years ago today) after the US government demonstrated that they could limit accuracy over any region they chose if they ever need to[1]. Most GPS receivers now implement crippled behavior at certain altitudes and speeds, but nobody assumes this to be a dependable defense.

1: "Additionally, we have demonstrated the capability to selectively deny GPS signals on a regional basis when our national security is threatened." from http://www.faa.gov/about/office_org/headquarters_offices/ato...

spitfire• 11 years ago

There's more than just SA at work here.

There's still speed and altitude limits in force via ITAR (arms trafficking regulations) that GPS manufacturers are not allowed to report GPS data. I think it something like 512 m/s and 18000M.

vinhboy• 11 years ago

A while back I was interested in building a DIY GPS after watching Lost. I day-dreamed about being stranded somewhere remote and building myself a GPS out of spare parts like MacGyver or something.

After finding this article, I realized that would be an impossible task without an engineering degree.

Has anyone found a more "For Dummies" version of this?

krapht2• 11 years ago

I don't know if "For Dummies" is possible for building a GPS system from first principles.

If you want to really learn by building, I recommend "Fundamentals of GPS Receivers: A Hardware Approach" by Dan Doberstein, and building the analog GPS system described in the first few chapters.

If you simply want to play with GPS, I'm sure there are many breakout modules from Adafruit et al.

contingencies• 11 years ago

GPS system from first principles.

To be fair, that would probably be navigation by naturally observable indicators such as the rising or setting sun, shadows over the day, locally / seasonally reliable stars for your area, and knowledge of local fauna/wave patterns.

After getting interested in sailing again (after 20 years) last year through multihull vessels, I started reading about the evolution of multihulls in the Pacific and then began looking at traditional navigation techniques. Following that, I was wondering for fun whether it would be possible to plot one's position given a rough time, rough position guestimate, and perfectly measured horizonal inclination, lens property and visible to 'the naked eye' star positions (ie. visible to the naked CCD at evening time = high ISO, noise and short shutter speed to failitate clarity in rough seas). My conclusion was yes, it's possible, with sub-GPS accuracy but accuracy which would be good enough to get you reliably between certain locations in certain seasons even on a sailboat.

I was surprised to read that some ICBMs allegedly used astronomy and pre-loaded landform navigation to avoid issues with jamming, and that fat databases of precise naked-eye type visible star locations are widely available, indeed so is software for reducing them to identities from an image input.

bainsfather2• 11 years ago

"The best fix so far was ±1 metres at a very open location using 12 satellites; but accuracy is typically ±5 metres in poorer locations with fewer satellites."

That seems very good accuracy. The off-the-shelf GPS I have (https://www.adafruit.com/products/746) is always >= ±5m, even with 360 degree view of the sky.

(the specs for my GPS claim < 3 meters, and also say "(all GPS technology has about 3m accuracy)").

CONTRARlAN3• 11 years ago

Commercial-grade technology has about 3m accuracy, but different methods can yield down to 10cm accuracy:

https://en.wikipedia.org/wiki/Global_Positioning_System#Prec...

And then there's a whole segment of survey-grade equipment that can get within a centimeter or two:

http://water.usgs.gov/osw/gps/

jhayward3• 11 years ago

That MediaTek chip is capable of better. Do you have WAAS (SBAS) enabled? 5m is about what you'd expect without the improved orbit/clock/ionosphere corrections.

It also pays off to use a good antenna, or at least put a ground plane beneath a mediocre one to block multipath reflections from the surrounding ground objects.

bainsfather2• 11 years ago

I just used the default settings. Didn't know about WAAS - thanks for pointing me to it.

From reading some forum posts, it seems you have to explicitly enable WAAS - I'll give that a try and see how much it helps.

jevinskie2• 11 years ago

The author got a lot further than my attempt! [0] I was attempting to make a Python-based GPS signal generator for later use in testing a pure VHDL/FPGA (no embedded CPU) receiver.

[0] https://github.com/jevinskie/jevps

Homemade GPS Receiver

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