[time-nuts] New GNSS chipsets

Magnus Danielson magnus at rubidium.dyndns.org
Mon Apr 2 09:15:25 UTC 2018


Hi Tom,

It is indeed a benefit to use the different constellations. However, I
want to make one point regarding propagation delay. As you observe one
satellite in 2 frequencies, you can use the fact that the ionospheric
shift at one frequency depends on the frequency and the TEC of that
path. As you now observe on two frequencies, you can now on the
difference between the measures estimate how much the difference of
frequency picked up at TEC, thus one can separate out the TEC effect. By
estimating TEX from those observations, the ionspheric effect can be
removed from both observations. If you try to do this with another
constellation, you add a number of complicating factors and loose
precision as you do so. Can you observe the same satellite in three
frequencies, you can build a more accurate estimation and compensation.
Also, you an loose one of the signals and still be able to perform the
processing. One should be prepared to do L1 only, L2C only, L5 only, L1
& L2C, L1 & L5, L2C & L5 and finally L1 & L2C & L5.

Cheers,
Magnus

On 04/01/2018 11:53 PM, Tom Knox wrote:
> Hi All;
> 
> I think the real break through is using these different constellations and their different frequencies and looking at carrier phase verses timing elements. This should allow the removal of propagation delay.
> 
> Cheers;
> 
> Thomas Knox
> actast at hotmail.com
> 
> 
> ________________________________
> From: time-nuts <time-nuts-bounces at febo.com> on behalf of Magnus Danielson <magnus at rubidium.dyndns.org>
> Sent: Sunday, April 1, 2018 2:40 PM
> To: time-nuts at febo.com
> Cc: magnus at rubidium.se
> Subject: Re: [time-nuts] New GNSS chipsets
> 
> Joe,
> 
> I'm not sure I had much influence, but I at least try to advocate for it
> to become a good market, so hopefully it will be affordable. It has
> actually been affordable for quite some time, so going multifrequency
> should be the next step and with that the benefits.
> 
> Cheers,
> Magnus
> 
> On 04/01/2018 07:04 PM, Joseph Gray wrote:
>> Magnus,
>>
>> When I can buy one of these new, multi-frequency receivers, I'll remember
>> to thank you :-) I wonder if any of the three will be available this year.
>> The Broadcom chipset in phones will be nice, but I'd also like a standalone
>> module from anyone. More fun stuff to play with.
>>
>> Joe Gray
>> W5JG
>>
>>
>> On Sun, Apr 1, 2018 at 3:15 AM, Magnus Danielson <magnus at rubidium.dyndns.org
>>> wrote:
>>
>>> Hi Joe,
>>>
>>> On 03/31/2018 01:16 PM, Joseph Gray wrote:
>>>> I've been reading announcements by Broadcom, uBlox and ST Micro for new
>>>> chipsets that will use L1, L2, L5 to provide significantly more precise
>>>> positioning for every day applications like cell phone, autonomous
>>>> vehicles, UAV, etc. Broadcom is claiming 30 cm, uBlox just says
>>> "centimeter
>>>> level". The next few years ought to be very interesting, as these
>>> chipsets
>>>> become available in consumer products.
>>>
>>> I have advocated for receivers able to handle multiple frequencies and
>>> multiple GNSS for some time, sneaking it into documents, so there should
>>> be some preparations for this now.
>>>
>>> The benefit is naturally redundancy, but also higher precision.
>>>
>>> Natural I would enjoy cheap multi-frequency receivers myself, but I
>>> would never admit that this would be a reason for advocating it. ;-)
>>>
>>> Cheers,
>>> Magnus
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