[FOSS-GPS] Mobile Robot Experimentation

[Yanqing]

If the baseline is less than 100 meters, it is definitely not needed to consider the ionospheric delay. I guess the error source may be from different multipath for the two receivers.

Maybe it will work if you change the standard deviations of the observations. 

Kind regards,
Yanqing

> On 18 Sep 2014, at 14:16, "Sean Hyde" <sean.a.hyde at gmail.com> wrote:
> 
> 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>:
> 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> 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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