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Comment by plantain | Hacker News Reader

There is nothing about aviation GPS's that make them high accuracy. In fact they're mostly inferior to consumer GPS equipment.

What drives up the cost is certification of the equipment.

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Certification and also a lot more technology behind figuring out when the position data is inaccurate. Aviation GPS units will run forward looking simulations (for example when flying a GPS landing approach) and figure out that satellites are about to be in a suboptimal position and warn the pilot accordingly.

That's still a simple thing to do with software. The cost of the device shouldn't go up because of that.

That makes no sense, unless your software guys work for free. The cost of software development has to be paid for out of the price of the devices. Aviation is a very limited market, so you don't have a lot of sales to amortize those costs.

The sales volume of consumer GPS units, however, is extremely large; if there is any pure software improvement to be made, even if the benefit for those devices is quite low, I'd expect it to be commonplace. Does anyone have a citation for aviation GPS using more sophisticated algorithms than consumer GPS?

Aviation stuff isn't necessarily an improvement for consumer units, though. For example, an aviation unit used for precision approaches or collision avoidance needs to detect when accuracy decreases below minimums, alert the pilot, and disable the functionality. For a consumer unit you just keep pumping out inaccurate, best-effort numbers.

Most GPS devices I've used provide a precision estimate already.

How accurate is that precision estimate, though? Is it built with enough care that you can put lives on the line?

Appeal to fear isn't an argument. Either the precision is right or it isn't. Precision requirements aren't unique to aviation and aviation doesn't even have the strictest requirements. The required precision of surveying equipment is much higher than what aviation needs.

I would have much more faith in an open source project with lots of people independently verifying the precision of calculations for known devices than closed source stuff from aviation companies that hide behind fear rather than real justifications for the price.

It's not an appeal to fear. It's an appeal to testing and verification.

The cost of these devices are much greater than the cost to implement the feature we are talking about though (alerting on bad precision). You can argue that the cost should be high because of intelligence about runway approaches, but just knowing that the precision is bad is not an excuse.

From a practical perspective that may be true.

Consumer GPS (eg. Phone/Tablet) is typically augmented GPS, whereas certified aviation GPS uses WAAS (Wide Area Augmentation System) to improve accuracy.

The key difference is that aviation GPS will warn the pilot if there is degraded performance below requirements, whereas consumer GPS doesn't.

Here is one ICAO paper on ADS-B accuracy: http://www.icao.int/APAC/Meetings/2011_ADS_B_SITF10/IP10_AUS...

Aviation GPS typically have a greater update rate, and support WAAS (wide area augmentation system) and RAIM (receiver autonomous integrity monitoring).

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