[time-nuts] Novatel Dual frequency GNSS receivers on ebay

Christopher Hoover ch at murgatroid.com
Tue Oct 10 16:33:54 EDT 2017


Tom,

Please see:

  https://www.novatel.com/assets/Documents/Manuals/om-20000128.pdf

  https://www.novatel.com/assets/Documents/Manuals/om-20000129.pdf


OEM628 and OEM638 boards can take an external frequency reference
(218/4.10.5), but OEM615 cannot.   I've never tried it.


To get the exact time of the PPS you need to enable the TIME message
(219/3.2.173) with something like (untested):

  LOG TIMEA ONTIME 1



A typical way to use the Novatel solution is to wire signals for the events
of interest -- say a camera shutter or start of frame (SOF) or a LIDAR
start of scan (SOS) -- into the receiver on one of the several event inputs.

With a suitable configuration, the log will contain messages with the
current 6-dof + time solution for the event edges.

If you are also logging the full receiver state, you can post-process the
events into better 6-dof + time solutions.



-- Christopher
73 de AI6KG








On Mon, Oct 9, 2017 at 1:02 PM, Tom Van Baak <tvb at leapsecond.com> wrote:

> Christopher,
>
> Thanks for that additional information. Can you (or Gregory) also comment
> on the external frequency input / output and the 1PPS output of this
> receiver?
>
> A quick look at the om-20000128.pdf and om-20000129.pdf documents has
> words like "better than 250 ns accuracy" and "50 ns increments" but I
> didn't see mention of 1PPS quantization, sawtooth correction, or other
> words commonly used in GPS timing receiver specifications. I'm guessing
> this product is mostly designed for the PN part of PNT (Positioning,
> Navigation, Timing)?
>
> /tvb
>
> ----- Original Message -----
> From: "Christopher Hoover" <ch at murgatroid.com>
> To: "Discussion of precise time and frequency measurement" <
> time-nuts at febo.com>
> Sent: Monday, October 09, 2017 12:35 PM
> Subject: Re: [time-nuts] Novatel Dual frequency GNSS receivers on ebay
>
>
> >I have quite a bit of experience with Novatel hardware include OEM6, CPT
> > and SPAN.
> >
> > CPT is an IMU made by KVH and relabeled by Novatel.    The accelerometers
> > are MEMs and the roll rate sensors are FOGs.   Pretty old design.
> > Performance is decent (but not auto alignment good).
> >
> > http://www.kvh.com/Military-and-Government/Gyros-and-
> Inertial-Systems-and-Compasses/Gyros-and-IMUs-and-INS/IMUs/CG-5100.aspx
> >
> > SPAN is the "solution."    SPAN-CPT puts the CPT IMU and the receiver in
> a
> > single box.   You could also get just the CPT in a box.
> >
> > The feature set enabled depends on the software keys that are loaded.
> > Caveat emptor.
> >
> > Dual receiver (even if you have the hardware) and ALIGN feature are extra
> > features.
> >
> > Also worth noting is that the circular connectors used on some of the
> > hardware are pricey.  Some are impossible to assemble without specialty
> > tools.
> >
> > -- Christopher.
> > 73 de AI6KG
> >
> >
> > On Sat, Oct 7, 2017 at 2:36 PM, J. L. Trantham <jltran at att.net> wrote:
> >
> >> Any idea what they are selling for at this time?
> >>
> >> I see that some sold for the BIN price of $349.99 up until June 20.
> After
> >> that, 'Offer Accepted' occurred up through October 5, with a BIN price
> now
> >> of $649.99, all plus $40 shipping.
> >>
> >> Joe
> >>
> >> -----Original Message-----
> >> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of
> Gregory
> >> Maxwell
> >> Sent: Saturday, October 07, 2017 2:17 PM
> >> To: Discussion of precise time and frequency measurement
> >> Subject: [time-nuts] Novatel Dual frequency GNSS receivers on ebay
> >>
> >> There is an ebay listing for "Novatel GPS-702-GG with SPAN-CPT Single
> >> Enclosure GNSS/INS Receiver + Cable" with a fairly large number
> available.
> >>
> >> This is a Novatel OEM628 dual frequency receiver (supports GPS, Glonass,
> >> SBAS, apparently including L1C and L2C), plus a three fiber ring gyros
> >> (with bias performance that blows away any mems gyro I've ever used)
> and an
> >> 3-axis mems acceletrometer in an aluminum case, plus a decent dual
> >> frequency antenna.  This is a generation-ish old kit.
> >> The industrial casing conspires to make it look somewhat less modern
> than
> >> it actually is.
> >>
> >> The receivers have external clock input (though not plumbed to the
> outside
> >> of the case) which appears to work though I didn't try much with it yet.
> >> Mine came with 2013-ish firmware but easily upgraded to current (2016)
> >> firmware. There is a windows based firmware update tool which talks to
> it
> >> over serial and is very straight forward (The firmware update
> OEM6631.zip
> >> can be found via google).
> >>
> >> You can communicate with them over serial in ascii, there is extensive
> >> firmware documentation that goes over every command
> >> https://www.novatel.com/assets/Documents/Manuals/om-20000129.pdf  some
> of
> >> which are specific to other modules. There is also a separate manual for
> >> the inertial navigation specific features (NovAtel SPAN-CPT Users
> >> manual.pdf)
> >>
> >> The external clock should allow you to hang it off a more stable
> >> oscillator which will improve the stability of the GNSS results, and _I
> >> presume_ improve the quality of the PPS output-- the firmware manual and
> >> operating manual are thin on details, and mostly just go into telling
> you
> >> how to adjust the kalman filter constants for different clock types.
> >>
> >> These also appear to support the novatel 'align' mode where you serial
> >> connect two receivers separated by a short baseline and get really
> accurate
> >> absolute headings; I'm planning on trying that that but haven't set it
> up
> >> yet.
> >>
> >> Looks like uber (last position was ubers offices in denver) had a fleet
> of
> >> these things. The couple I got run great, including the IMU, the
> antennas
> >> obviously spent a long time outside, but work fine. The cable they come
> >> with is weird, but I had no problem chopping one end off and figuring
> out
> >> the pinout (see bottom).
> >>
> >> The novatel OEM6 is well supported by rtklib and I was able to get
> >> post-processed positions very easily.
> >>
> >> Seller takes best offers a fair amount below the $649 asking price.
> >> Looks like they may have another 30 or so of them.
> >>
> >> May be useful for doing time transfer especially with the clock input.
> >> Just using it to get nice dual band observations to precisely survey an
> >> antenna location for a traditional GPSDO may improve GPSDO performance
> by a
> >> fair amount.
> >>
> >> Here is the signals and wire colors on the cables mine came with.
> >> YMMV, I'd suggest not blindly trusting that colors match on other
> >> units.    These cables don't plumb out many of the signals from the
> >> module (in particular, they don't carrying COM2, which is why I haven't
> >> tried multi-receiver headings yet, since I'd need to figure out how to
> talk
> >> to it over USB if com1 is in use for that), I'm unsure if they're wired
> >> through the to external connector.
> >>
> >> 01 white          power return (-)
> >> 02 brown          9-18 VDC power input (+)
> >> 03 yellow        COM1 RS232 TX
> >> 05 pink           COM1 RS232 RX
> >> 09 green          COM1 GND
> >> 10 black          USB D+
> >> 11 purple         USB D-
> >> 12 yellow brnstp  USB GND
> >> 15 red            ODO SIGA
> >> 16 blue           ODO SIGA-inv
> >> 29 grey pinkstp   PPS (high resistance? 80 ohm)
> >> 30 whitw grnstp   Event1
> >> 31 red blustp     signal ground
> >> _______________________________________________
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