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Comment by walrus01 | Hacker News Reader

I understand it's probably because the GPS functionality is integrated into the same RF chipset that's handling wifi/bluetooth, but it would be possible to make a "no transmit capability" camera that still has GPS metadata functionality, with GPS receiver chip and an antenna tuned for 1400-1600 MHz, since ordinary consumer grade GPS is a receive-only technology.

But that would still possibly present a problem for serious government use where it can't have an antenna of any form in it.

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The camera (even the regular model) does not have its own GPS receiver at all. It relies on a smartphone to transmit GPS coordinates over Bluetooth.

This is pretty common in modern cameras, presumably because most photographers expect to be able to turn their cameras on and off very rapidly, and it would be difficult to maintain a GPS fix with that usage pattern.

I don't think it's impossible. We aren't talking RTK here, you should be able to get a usable fix quickly. You also have some other advantages. For starters, the GPS coordinate doesn't need to be taken at the exact instant the photo is taken. If it takes a second to get the coordinate, that can be done in the background while the photographer continues to do their thing. Another advantage is that people never hold their cameras upside down, so the antenna can be pretty directional.

> people never hold their cameras upside down

I'm not to sure about that. I rarely keep my camera (close to) fully horizontal.

Also for macrophotography when you want to have the camera very close to the ground on a tripod, upside down is often used.

Turning your camera upside down is an old trick to see over crowds, since the viewfinder is now at the bottom.

This trick is also used extensively in submarines.

You don't have to. There are GPS satellites along the horizon too. As long as it isn't literally upside down.

Getting a GPS fix from the satellites alone with no internet connection or stored data takes a few hours, not seconds. First you have to listen to the very slow data channel that tells you where the satellites are that takes a few hours to transmit the complete set before repeating.

I'm no expert on GPS, but once you have the stored data it's good for several days isn't it? So after the first fix it shouldn't be too onerous.

That works for phones (and you can download it from the internet if out of date). It doesn't work for cameras which are usually turned off until you want to take pictures.

All I know is I've never seen the GPS module for my 10+ year old Pentax k30 take more than a few minutes to get a fix after months of having the battery completely removed, and it has no network connection.

> It doesn't work for cameras which are usually turned off until you want to take pictures.

The GPS almanac is valid for 180 days, so if you can save it (it's 15000 bits, ~1.8 kB), and keep time within ±20s and assuming a position of ±100km of your last fix, you can do a "warm" start with-in a minute:

* https://en.wikipedia.org/wiki/Time_to_first_fix

A completely cold start takes less than 15 minutes.

And yes, cameras are usually turned off, but they do still trickle some power to keep the on-board clock going: so as long as you use your camera once every six months, and in the same city, there's a good chance you'll get a quick fix.

This does not jibe with my experience with my long-in-the-tooth Garmin when it cannot connect to my phone and has been recharged after a total power down. It can take minutes but not hours.

No it doesn't, the time to first fix from cold start of modern GNSS receivers is in seconds (24s on the NEO M9N). Assisted GNSS using data from the internet reduces that to under 2 seconds (see https://content.u-blox.com/sites/default/files/NEO-M9N-00B_D...). Of course this can change based on the GNSS environment.

Even in the worst case the almanac (the data that is streamed at 50 bits/second) repeats every 12.5 minutes not hours.

> Getting a GPS fix from the satellites alone with no internet connection or stored data takes a few hours, not seconds.

It takes less than 15 minutes (in the worst case):

> The receiver is missing or has inaccurate estimates of its position, velocity, the time, or the visibility of any of the GPS satellites. As such, the receiver must systematically search for all possible satellites. After acquiring a satellite signal, the receiver can begin to obtain approximate information on all the other satellites, called the almanac. This almanac is transmitted repeatedly over 12.5 minutes. Almanac data can be received from any of the GPS satellites and is considered valid for up to 180 days.

* https://en.wikipedia.org/wiki/Time_to_first_fix

That's just false. I wrote firmware for cheapo GPS modules that got a DGPS fix in seconds. And there are other tricks you can play to bring the latency down, knowing the use case.

Well Nikon has a GPS module (Nikon GP-1, https://en.wikipedia.org/wiki/Nikon_GP-1) for the hotshoe that does work, so I dont think that is the issue. Also at least on my D850, turning off the camera does not turn off the bluetooth automatically, and it can sync photos to the smartphone while the camera is off, so depending on how much power GPS would use, it could be possible to have it run in the background. And turning it off keeps some things running anyway, like showing the number of photos still available, so coordinates could be saved for a little while after turning off.

I had a GP-1 at one point. It would take several seconds to get a GPS lock, so about a third of the time my images had no GPS or I had to wait for the light to indicate it was working. Not very practical in my case. Also it connected via an awkward cable.

Even if it only had RX-only RF capabilities, that means that is a vector for an inbound wireless attack. At the very least, the kind of places that restrict wireless devices probably do not want any pictures or other artifacts to exist tagged with precise location metadata.

>Can't have an antenna of any form in it.

All wires are antennas...

But the short wires in a Nikon camera are not long enough to be a useful antenna. In fact, I doubt there's really anything one would consider a wire in a camera body. Everything is probably just traces on a PCB.

There's enough space for one.

Traces can be antennas

Am I missing something? Most IoT devices use trace antennae

https://en.wikipedia.org/wiki/Microstrip_antenna

Trace antennas are very specifically designed shapes given the PCB material and other nearby components and structures. It’s never “just a trace”.

You’re right that traces can emit and receive RF, hence why things like FCC limits and testing exist even for unintentional emitters, but even failing devices which greatly exceed the limits have traces which are many orders of magnitude worse at being antennas than a typical trace antenna.

> But the short wires in a Nikon camera are not long enough to be a useful antenna. […] Everything is probably just traces on a PCB.

Anyone who's had to get newly developed hardware through EMI certification in recent times can tell you that it's quite easy to accidentally make PCB trace work as an antenna. Not necessarily a great antenna but enough to emit some random signal and fail certification. 3 GHz is 100mm in wavelength, and a quarter wavelength makes one of the simplest antennas… that's only 25mm. The whole story is much more complicated but the thing is that the scales are in range.

At >= 2.4ghz, you measure antenna length in mm.

Bluetooth antennas that are just traces on a PCB board are very common. Think about how small a bluetooth earbud can be and still get pretty incredible range.

I think you wrote this comment with the compiler’s pedantic warnings turned on.

If we're being pedantic, all conductors are antennas.

What is the point? As long as your camera has a decent clock, you just need to record a gpx during your shooting session with an external device and you can add geolocation after you download your pictures. IIRC Darktable can do that.

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