dannym at austin.rr.com
Wed Sep 26 23:15:09 PDT 2012
Wow, misspelled the unit. NV08C now. The company is NVS.
The units also receive Galileo & Compass, but Galileo is only sending
dummy data and Compass is only supposed to be on a trial basis (low
accuracy) right now.
On 9/27/2012 12:59 AM, Danny Miller wrote:
> I've been playing with the new NVS08C GPS, which Michele outlined in a
> Who wrote an RTKLib branch to support it.
> They're pretty remarkable. I have 2 units with identical patch
> antennas (also have Sarantel quad-helicals if I need 'em). These are
> cheap antenna I bought on eBay like a year ago, but they do seem to
> receive GLONASS sats nicely (the frequency is close). One thing to
> note, the spec sheet seems to say it provides "2.65 to 2.8V" of
> antenna power, which may not be enough. The reference schematic
> contains a resistor and cap pair needed to use voltages supplies from
> another rail (like 3.3v power for a 3.3v ant).
> Since they receive GLONASS as well as GPS, the constellation view is
> instantly quite huge, 20 sats isn't uncommon. In fact, on RAW, the
> serial bandwidth is "significant" and from the look of it 115200 may
> not be sufficient.
> The units' output is amazingly consistent. With a pair of static
> patch antennae on a groundplane, after about 30 sec they stop moving
> and rarely move more than a few cm. Given a couple of hours, you may
> see a track drift 1-2M, but it's a very smooth, noise-free track. If
> you move it in a 1M square you'll see a ~1M square on the track.
> That's without PPP or RTK, just watching the hardware solution. But,
> they're off by about 1-2M from my "best result" from a PPP static fix,
> and 1-2M from each other's solutions, too. But, they're HIGHLY
> consistent inside of a unit. If I move the antenna under a metal
> shield to kill the signal and bring it back out, the solution will
> restart within about 0.5M of its last lock.
> However, strangely, the RTK and PPP has so far been "off". That is,
> when RTK DOES get to "Fixed", sometimes it's Fixed within a few CM,
> but early on I get a lot of Fixed off my like 2-4M, and most of the
> time I only have Float. The Lea-6T worked more stable in RTK IIRC.
> It's odd because the simple non-RTK hardware solution can get better
> results, at least early on.
> I don't know if there might be a problem in the pseudorange/carrier
> phase/doppler resulting in what seems like relatively poor RTKLib
> performance, or maybe Michele's config or application code has
> something strange, or maybe RTKLib has trouble with an unusually high
> number of sats? (I guess I could retry that with GLONASS support
> disabled to go back to a more modest number of sats).
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