[FOSS-GPS] RTKLIB Vehicle Accuracy

Tue Jul 1 13:46:38 PDT 2014

> where we used 23 meters of RG58,
RG58 would be ill advised here (too much loss at L band)
We use RG174 for moderately long runs and for temporary runs where 
vehicle can damage the coax.
It is thin and it is tough.

You can get a 500 foot spool from L-com and others for a modest price if 
crimping SMA connectors would not be a problem.

If you are putting up a reference station and can use the larger 
diameter cable (which has less loss - a must for longer runs) then RG213 
is to be preferred.

I am amazed to see reports that these small patch antennas allow 
obtaining fixed results.  In the absence of a good ground plane I have 
had poor results, and even when it worked needed to try and calibrate 
out the phase angle biases.  [I work in an automotive environment where 
we typically use a more costly antenna simply because we do not want 
that as a factor]

Nick, is the link you provided below good?, seem to go to a page with a 
small patch ant not plot results.

Regards
David Kelley

On 7/1/2014 1:16 PM, Anton Strydom wrote:
> Hi Nick
>
> No for the base I use the Leica GG02 L1/L2 and only use the LEA6 T on the
> roving units
> I will save a plot and send it to you to show you the results I get.
>
> What coax to you use? I normally use either LMR 400 where I can use TNC
> connectors and 173 where I use SMA but then not longer than 10 cm of 173.
>
> I have had a situation where have a Leica SR 500 base and a AT504 antenna
> where we used 23 meters of RG58, we had lots of problems with the base. I
> changed the coax to LMR 400 and did not have any problems after the change
>
> Regards
>
> Anton
>
>
> On Tue, Jul 1, 2014 at 10:07 PM, Nick Østergaard <oe.nick at gmail.com> wrote:
>
>> Ok, interresting. Is is working with the patch on both rover and base?
>> I have tried with a setup, but I had had very bad results, especially
>> when I moved. Attached is results I have had, and that with antennas
>> as [1] with bias voltage on and half a meter of coax. The signal is
>> great as far as I remember. I have LEA6T's also (maybe 4T), although I
>> don't quite remember exactly, it is quite some time ago since I tried.
>>
>> Attached is a post processed result.
>>
>> [1]
>> http://dk.rs-online.com/web/p/smt-antenner/7239151/?searchTerm=SM-1575&relevancy-data=636F3D3226696E3D4931384E4B6E6F776E41734D504E266C753D6461266D6D3D6D61746368616C6C7061727469616C26706D3D5E5B5C707B4C7D5C707B4E647D2D2C2F255C2E5D2B2426706F3D313326736E3D592673743D4D414E5F504152545F4E554D4245522677633D424F5448267573743D534D2D3135373526
>>
>> 2014-07-01 21:38 GMT+02:00 Anton Strydom <agstrydom at gmail.com>:
>>> Hi Nick
>>>
>>> Yes I get a reasonable plot using that specific unit. However for what we
>>> intend doing in the long term we will be using a different design helical
>>> antenna that we are in the process of developing.
>>>
>>> The units in the photographs are only for testing and setting up but we
>> get
>>> good results. For communication we use cellular routers connected to
>> Leica
>>> GGO2 L1/L2 base or else we use 3D Robotics XBEE radios. On the roving
>> unit I
>>> use an ARM processor where I have 4 rs232 ports available. It works very
>>> well and is very stable.
>>>
>>> The radios I use where i have no cellular coverage.
>>>
>>> Attached is a photograph of  the base setup
>>>
>>> Regards
>>>
>>> Anton
>>>
>>>
>>> On Tue, Jul 1, 2014 at 9:27 PM, Nick Østergaard <oe.nick at gmail.com>
>> wrote:
>>>> Hi Anton
>>>>
>>>> Really? You get by with that small patch antenna? Is that a good (green
>> in
>>>> rtkplot) RTK solution you get from that constant?
>>>>
>>>> Regards
>>>> Another Nick
>>>>
>>>> Den 01/07/2014 21.11 skrev "Anton Strydom" <agstrydom at gmail.com>:
>>>>
>>>>> Hi Nick
>>>>>
>>>>> I have done a lot of testing with U-Blox LEA 6T at speeds of up to 120
>> km
>>>>> / h. Lat & Lon does not appear to be a problem but elevation is a
>> problem. I
>>>>> paid the equivalent of $60 for the 2 receivers and ceramic patch
>> antennas.
>>>>> They are accurate on base line up to 10km where after accuracy
>>>>> drastically degrades.
>>>>>
>>>>> I do all my testing in real time and do not post process.
>>>>>
>>>>> If you want to I can speak to my supplier and see if they still have
>> some
>>>>> of the LEA 6T's in stock at the price I paid for them.
>>>>>
>>>>> Attached are photographs of the units I am using
>>>>>
>>>>> Regards
>>>>>
>>>>> Anton
>>>>>
>>>>>
>>>>> On Tue, Jul 1, 2014 at 8:50 PM, Danny Miller <dannym at austin.rr.com>
>>>>> wrote:
>>>>>> It does work in moving.  But signal problems do still make the
>> position
>>>>>> jump around, trees and buildings and an antenna's orientation
>> changing can
>>>>>> make an error happen.  Antenna quality has a lot to do with that, too.
>>>>>>
>>>>>> RTKLib requires a GPS with RAW pseudorange outputs.  The NV08C is a
>>>>>> good, cheap one to do it:
>>>>>>
>>>>>> http://www.nvs-gnss.com/contacts.html
>>>>>>
>>>>>> Contact your local sales rep there- it was actually easy in my
>>>>>> experience to order a couple from them, and oddly cheaper than Newark
>>>>>> element 14, as well as quicker to ship.
>>>>>>
>>>>>> Danny
>>>>>>
>>>>>>
>>>>>> On 7/1/2014 1:24 PM, Nick wrote:
>>>>>>
>>>>>> Hello,
>>>>>>
>>>>>> I am interested in getting an RTK GPS setup working for a moving
>>>>>> vehicle, not fast, perhaps 10 mph. I would postprocess the data
>> collected
>>>>>> later, using data downloaded from a nearby station.
>>>>>>
>>>>>> My desire is to log elevation data every few seconds as the vehicle
>>>>>> drives. I hope to achieve 10-20 cm accuracy for the position and the
>>>>>> elevation.
>>>>>>
>>>>>> As I research RTKLIB, it seems like most information I come across is
>>>>>> regarding a static location. Is my goal feasible to achieve this kind
>> of
>>>>>> accuracy as the vehicle moves?
>>>>>>
>>>>>> If so, can anyone recommend a good board to get me started? I'm hoping
>>>>>> to be able to do this for under $200 (just one receiver since the base
>>>>>> station is public) -- please give me a reality check if this is
>> unlikely.
>>>>>> Thanks,
>>>>>>
>>>>>> Nick
>>>>>>
>>>>>>
>>>>>>
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-- 
Regards,
David Kelley
ITS Programs Manager
SubCarrier Systems Corp. (SCSC)
1833 East Foothill Blvd. Glendora, CA USA  91741
626-485-7528 (Cell)      888-950-8747 (Main)
626-513-7715 (Office)    888-613-0757 (Fax)
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