[FOSS-GPS] Post-processing RINEX to simulate RTK
Mauro Ugarte Avilés
mauro.ugarte at cefop.udec.cl
Fri Jun 29 15:29:23 PDT 2012
Dear Antonio, that's a great experiment....I'll be glad to get my hands
on a L1+L2 20 Hz receiver some day....your results are far from a small
progress, IMHO. :-)
How is turning out the comparison? how similar are both results for the
same data?. It would be excellent that RTKLIB/RTKPOST could be validated
with that level of data and experiments against those "well known
top-level proffesional" (and very expensive) closed software suites, at
least for some level of performance or for some defined applications.
Regarding the wireless testing, at our lab we have some "in the field"
experience in data links on 400, 900 and 2400 Mhz (WiFi), so feel free
to ask if you ever need some advice.
The theoretical concepts behind GNSS positioning are like diving: the
deeper you go, the darker it gets, especially if the electromagnetic
signals, carrier modulations, pseudorandom Gold codes correlation and
phase shifts by the Doppler effect aren't on your everyday range of
worries....(neither did I recalled all this stuff when I went diving on
GNSS positioning trying to understand it, and as an electronic
engineering student all those concepts should be "natural" for me,
supposedly :-)....eventually I did decipher most of the "magic" behind
this system, but when I got to face ambiguity resolution I just gave
up....I'm hoping to find time again to dive THAT deep.....but now if the
results are good enough to challenge commercial well known top level
software-hardware, I'll be focusing on applications for it!
Best regards, thanks for that fast and complete answer, and good luck on
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 29/06/12 13:09, António Pestana wrote:
> 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.
> 2012/6/29 Mauro Ugarte Avilés <mauro.ugarte at cefop.udec.cl
> <mailto: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 <mailto: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
>> <mailto: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:
>> with both antennas (the AP/router and the USB adapter)
>> replaced by a directional Wifi antenna like this one:
>> 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
>> My structures move at relatively high frequencies (say from 0,1
>> to 5 Hz). Most of the movements are small (a few centimeters at
>> Best regards
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