Re: SparkFun GNSS L1/L5 Breakout - NEO-F10N, SMA - GPS-24114 - SparkFun Electronics

[Frank Nicholas]

> On Mar 25, 2024, at 5:17 PM, Greg Troxel <gdt@lexort.com> wrote:
> 
> Chris Kuethe <chris.kuethe@gmail.com> writes:
> 
>> I saw a brief comparison of GNSSes that said GPS has better accuracy than
>> GLONASS, and that Beidou and Galileo have similar accuracy which is better
>> than both GPS or GLONASS. I'm not really equipped to properly
>> test/validate/refute that claim, or even appreciate it.
> 
> Per-system accuracy is one thing, and net accuracy from an ensemble is
> another.  It's also not just accuracy, it's odds of working.
> 
>> OK, it's cool that
>> my cell phone can simultaneously use GPS (L1/L5), GLONASS (L1), Beidou
>> (B1/B2a), and Galileo (E1/E5a). I've got a home time server which I haven't
>> bothered to measure cable propagation delay or interrupt latency on because
>> 1-millisecond time sync is quite sufficient for my uses (log file
>> timestamps, correctly setting the time on my telescope controller, and
>> programming the timer on my coffee maker). I would hope that my
>> multi-constellation receivers are all smart enough to figure out which
>> combination of satellites provides the best navigation solution..
> 
> The L1/L5 is interesting, vs L1/L2.    I don't really understand why
> there are L1/L5 only receivers given how L2/L5 are close.   It may be a
> perception that L2 is going away, but that seems premature.  My
> impression that there are more L2 signals available than L5, but maybe
> with Galileo that isn't true.

Not that I know anything about it, but Sparkfun’s product page states, 
“Utilizing the L5 band, the NEO-F10N delivers improved performance under 
challenging urban environments. The L5 signals fall within the protected ARNS 
(aeronautical radio navigation service) frequency band, leading to less RF 
interference.”


I haven’t looked at Ublox’s chipset product page…

>> Gary share his thoughts about why an absence of GLONASS support might be a
>> feature; from my perspective it doesn't seem to offer any compelling
>> advantages over GPS. It doesn't look like civilian multi-frequency are
>> readily commercially available which would allow you to directly probe
>> ionospheric effects. If you've got limited resources (tuners, correlators,
>> DSPs, memory, CPU) in your receiver, maybe you want to use more of them for
>> more useful systems. At least GPS has some usable L5 satellites.
> 
> Prioritization schemes are one thing, but most receivers these days have
> a ton of channels.
> 
> I speculate, wildly and without basis, that the GLONASS signal structure
> being different (not just CDMA) is a reason that omitting it can result
> in a lower cost, both BOM and NRE.  And that with Galileo and BeiDou,
> skipping GLONASS doesn't hurt much.
> 
>> I dunno, maybe you have really restricted sky view in one location and
>> GPS+GLONASS might give you just enough satellites to get a usable fix?
> 
> Indeed, a fair point.   But I find in a multi-constellation receiver
> that there are often 30 sats above the horizon.