[FOSS-GPS] Mobile Robot Experimentation

Thu Sep 18 05:16:29 PDT 2014

Hi Antonio,

I’m glad to hear you say this as the NV08C manufacturer makes a big deal of
using this module to do this using RTKLIB and I was getting worried.

The base station and the rover are much closer than 100m.

-Sean

From: foss-gps-bounces at lists.osgeo.org
[mailto:foss-gps-bounces at lists.osgeo.org] On Behalf Of António Pestana
Sent: Thursday, September 18, 2014 4:06 AM
To: Open Source GPS-related discussion and support
Subject: Re: [FOSS-GPS] Mobile Robot Experimentation

If rover and base are close enough (say, no more than a few hundred meters
apart) ionospheric refraction pseudoranges disturbances will be pretty much
the same both for base and rover. Therefore mono-frequency observations will
suffice.

Antonio

2014-09-18 8:50 GMT+01:00 Yanqing <fishloveocean at gmail.com
<mailto:fishloveocean at gmail.com> >:

Dual frequency receivers could solve this problem. You need both the rover
and the base station receivers to be dual frequency.

Kind regards,

Yanqing

On 18 Sep 2014, at 03:02, "Sean Hyde" <sean.a.hyde at gmail.com
<mailto:sean.a.hyde at gmail.com> > wrote:

Thanks for the responses!  I apologize for breaking the thread, but I had
turned on Digests by accident and couldn’t figure out how to reply to
individual messages.

“I'm not sure what receivers you are using, but if it's this one: 
http://www.nvs-gnss.com/products/receivers/item/2-nv08c-csm.html it seems 
to be L1 only, not L1+L2.  The antenna you are using covers 1574-1610 MHz, 
so while multi-system (GPS/Glonass) it is also L1 only. The GPS L2 
frequency is quite a bit lower, at 1227.6 MHz.
http://en.wikipedia.org/wiki/GPS_signals#Frequencies_used_by_GPS

As far as I know, GPS L1+L2 receivers start around $750 used (eg. Trimble 
4000ssi on ebay) and much more new.

“

Hi John.  I had completely overlooked the fact that the NV08C couldn’t
utilize L2 as I had read a lot of information about using it in RTK setups.
I’m rather new to GPS.  My understanding is that without L2 I will not be
able to get rid of ionospheric delay, which will increase error.  Could this
be why my system isn’t performing as I hoped?  Can I get away with using an
L1+L2 receiver on the Base Station and not on the Rover?

“Did you try with simultaneous mode of ambiguity resolution and use a
smaller min ratio to fix ambiguity, such as 2 or 1.5?

Kind regards,
Yanqing

“

Hello Yanging.  I tried instantaneous mode and it seemed much worse.  My
Float solutions oscillated by several meters (instead of a tens of
centimeters with a drift) and I couldn’t get a Fix.  I tried reducing the
ratio in the other modes.  Although that got me a fix more easily, I was
concerned that it wasn’t accurate, as it was not repeatable.  

-Sean

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