Re: Assisted GPS UBlox7

[Mike]

On Thu, Nov 16, 2023 at 08:42:33PM -0800, Gary E. Miller wrote:
> Yo Mike!
> 
> On Fri, 17 Nov 2023 00:08:26 +0000
> Mike via <gpsd-users@nongnu.org> wrote:
> 
> > On Tue, Nov 14, 2023 at 11:07:28AM -0800, Gary E. Miller wrote:

Hi Gary,

Thanks for your continued support.

> 
> > 1) You mentioned newer receievers could be had for not much money.
> > What should I be looking out for when buying a receiever?  My 7-series
> > was cheap and puchased a year ago, so on the face of it, it does
> > appaer to meet the criteria of "newer" and "not much money" :-)  I'm
> > relutant to ask for recommendations, as it's like asking people to
> > take sides in a marital dispute, nevertheless, do you have any
> > recommendations / suggestions, please?
> 
> Not knowing your use case, I can only throw out a few suggestions:
> 
> Here is a NEO-M8N for #13, it does GLONASS and GPS, and works much
> better than the M7N:
> 
> https://www.ebay.com/itm/183780263635

The device I had at the moment is a IPx6, USB receiver with magnetic
back, which is ideal for my use case.  It's connected to a Rapsberry Pi
and mounted on a metal plate, out in the elements.  A rudimentary Google
suggests that there are similar versions of the NEO-M8N, although it
looks from Greg's email that the magic phrase is "160-channel receiver".

> 
> 
> > 2) I'm curious to why the Ephermeris / Almanac download issue doesn't
> > afflict "newer receivers"?
> 
> Greg's email explains this.  A modern receiver can get TTFF, from cold
> in 29s.  1 s when hot.
> 
> > 3) I'm a little perplexed as to why the Ephemeris data is so hard to
> > get hold of?
> 
> It not.  Getting it in the proprietary form that your u-blox needs
> is hard.  Its all about $$$$.

That would be that "market forces" thing.  Yes, I'm familar with that
:-)

Incidently, are you able to recommend a service for aquiring the Almanac
/ Ephemeris?  One that doesn't require "market forces"?

I was reading the UBlox manual here:

https://content.u-blox.com/sites/default/files/products/documents/u-blox7-V14_ReceiverDescriptionProtocolSpec_%28GPS.G7-SW-12001%29_Public.pdf

Which on page 36 does talk about sending the necessary data to the GPS
receiever and the linked pages do appear to explain the protocol.

I haven't doug into it in too much detail, as it's right on the edge of
my knowlege, although my initial impression is that anyoen with more
coding/comp sci/maths knowedge and a source of the data to hand could
get this working on more sane timescales than myself.

I also found the following code on GitHub:

https://github.com/gokuhs/ublox-agps

I see this uses a free trial and I haven't checked the format of the
data that is provided.

> 
> 
> > Surely I can't be the only person in the world with a
> > GPS receiever who's pondered sending the Ephemeris over a serial port?
> 
> All it takes is money, but very little to gain for that money.
> 
> > Surely any schmuck with a SDR can receieve the data from the GPS
> > system? I understand that while it's unusual for a GPS, the 7 series
> > will actually squirt the Ephermeris from GPS to host, if asked really
> > nicely.
> 
> Sure, gpsd can give you that Almanac.  Nut it can't convert it to
> he undocumente format that u-blox needs.
> 
> > The first thought that went through my head was, maybe I
> > should buy a 2nd one, leave it on the roof of my house and habe a
> > perl script downlod the data every few mins and stick it on a web
> > server.  Am I missing something?
> 
> Yeah, you need to proprietary program to encode it.
> 
> Easier to just buy an M10.
> 
> RGDS
> GARY
> ---------------------------------------------------------------------------
> Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
>       gem@rellim.com  Tel:+1 541 382 8588
> 
>           Veritas liberabit vos. -- Quid est veritas?
>     "If you can't measure it, you can't improve it." - Lord Kelvin

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