[FOSS-GPS] Post-processing RINEX to simulate RTK

Fri Jun 29 10:09:55 PDT 2012

Dear Mauro

Sorry from my very long silence.

I'm still testing the use of RTKLIB/RTKPOST to simulate "real-time"
kinematic positioning in structural monitoring. I'm afraid my progress is
still small.

We have done some experiments on the top of a 110 meters high viaduct pier.
At the time of this experiment the top of the pier could move freely. I've
collected 20 Hz GPS L1+L2 RINEX data both on top of the pier and at a
reference site, 1200 meters away. The processing of the RINEX files was
done mainly using "fix and hold" integer ambiguity resolution strategy.
I´ve got some interesting results:

a) A East-West 24-hours cycle oscillation was detected; I suppose that it
was due to the effect on the pier of the apparent diurnal movement of the
sun.
b) We were able to extract, from the displacements of the top pf the pier,
the first natural frequency of the pier (around 0.5 Hz)

For the last three months I have been conducting experiments to compare
RTKPOST processing of RINEX files with the RTK output of a very well known
top-level professional software (made by a very well known company). At the
same time I have been testing the use of wireless radio antenas to conect
the sation sites to the reference site.

Apart from this experiments I'm still strugling with some theoretical
concepts regarding GNSS positioning. It is still not clear to me the exact
meaning of a number of terms that I find here and there. I suppose that
there is still no uniformity in naming some key concepts of high-precision
(centimeter or sub-centimeter) GNSS positioning. And I still need to truly
learn the fundamentals of high-precision real time GNSS positioning, namely
the distinct ambiguity processing strategies and the different positioning
modes used.

Regards

Antonio

2012/6/29 Mauro Ugarte Avilés <mauro.ugarte at cefop.udec.cl>

>  Dear Antonio,
>
> It's been a while since we talked about RTKLIB and all those networking
> options.....how is it going?
>
> I would be glad to know something about your overall results, or some
> partial results regarding the monitoring of structures you where
> conducting.....I'm planning to learn a little bit of the absolute basics in
> the civil engineering fields where precise positioning could apply,
> particularly in the area of land surveying, in order to study possible
> solutions to some of it's requirements trough the use of rtklib.
>
> (Any other list memeber's comments about some experience in this
> particular application of precise positioning (RTK, PPP or even DGPS), are
> really welcome.)
>
> Best regards!
>
>
> Mauro Ugarte A.
> Ingeniero de Desarrollo
> División de Instrumentación Óptica y Tecnologías de Teledetección
> Centro de Óptica y Fotónica
> Universidad de Concepción
> F/Fax: 2204740 | mauro.ugarte at cefop.udec.cl
>
> On 26/10/11 19:05, António Pestana wrote:
>
>
>
> 2011/10/26 Mauro Ugarte Avilés <mauro.ugarte at cefop.udec.cl>
>
>>
>>  Regarding that chapter, you should use as your network topology, the
>> example 4 (Wifi) or 5 (mobile phone network), and replace on both of those
>> examples the block "RTKNAVI" by Spider (and maybe move Spider to the "Base
>> Station" or reference receiver's PC, and "STRSVR" to the remote receiver's
>> PC) . If there is going to be line of sight between both locations, a
>> Wireless Router or Access Point connected at the Base Station's PC Ethernet
>> port (or wirelessly), an a USB wireless adapter with detachable antenna at
>> the rover's PC (this one, for example:
>> http://www.tp-link.com/en/products/details/?model=TL-WN722N), with both
>> antennas (the AP/router and the USB adapter) replaced by a directional Wifi
>> antenna like this one:
>> http://www.tiendecita.com/antena-wifi-planar-estanca-marca-abaks-p-99.html,
>> should do it. (Note that the antenna does not include the coaxial cable
>> needed to connect the antenna to the AP/router (that by the way has to have
>> a detachable antenna also, in order to replace it), but that cable can be
>> easily found on computer stores). The USB wireless adapter used at the
>> remote receiver's PC should be placed inside the box behind the antenna,
>> were the RP-SMA connector is.
>>
>
>  Once again very useful tips. Thanks.
>
>
>>
>>  My fault, no examples...but at least RTKLIB has a manual....and there
>> are screen captures on it!! At the GNSS positioning techniques FOSS world,
>> those features are not very usual... ;-).
>>
>
>  Yes. I must agree with you. The manual is very good.
>
>
>> Based on that brief descriptions, you would be able to find better
>> explanations somewhere else: papers, doctorate theses, GNSS equipment
>> manufacturers, etc.
>>
>
>  That's what I'm trying to do these days...
>
>
>
>>  You will be sensing large structures, right? In that case, I would go
>> with "static" (static rover, static reference), not "moving-base" (moving
>> rover, moving reference) nor "fixed" (constant distance between rover and
>> base). Maybe you could go with kinematic too, if the real-time
>> displacements and deflections of the structures studied can be considered
>> as "movement".
>>
>>
>  My structures move at relatively high frequencies (say from 0,1 to 5
> Hz). Most of the movements are small (a few centimeters at most).
>
>  Best regards
>
>  Antonio
>
>
>
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