Trimble CenterPoint RTX? Post Processing FAQ's

Trimble CenterPoint RTX Post
Processing FAQ’s
What is Trimble RTX technology?
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13 May 2013
Trimble RTX TM (Real Time eXtended) is a high-­‐accuracy GNSS correction technology. By combining real-­‐
time data with innovative positioning and compression algorithms, RTX is able to deliver repeatable
high accuracy positions worldwide. RTX technology utilizes real-­‐time data from a global reference
station infrastructure to compute centimeter level positions based on satellite orbit and clock
information.
What services are enabled through the Trimble RTX Technology?
Trimble CenterPoint RTX is a correction service built on patent-­‐pending Trimble RTX TM technology.
Trimble RTX Technology now enables several different services:
• Trimble CenterPoint TM RTX TM Post Processing NEW!
• CenterPoint RTX TM Fast satellite delivery (1 minute convergence time)
• CenterPoint RTX TM Standard Satellite delivery
• CenterPoint RTX TM Standard IP delivery
• Trimble xFill NEW!
• Trimble RTX TM
• Trimble Pivot TM RTX
How does it Trimble RTX Technology work?
This new technology from Trimble leverages real-­‐time data from a global tracking station network along
with innovative positioning and compression algorithms to compute and relay satellite orbit, satellite
clock, and other system adjustments to the receiver, resulting in the high accuracies. These adjustments
are transmitted to the receiver via satellite, Internet Protocol (IP or Cellular), and now through post
processing delivery.
What is Trimble CenterPoint RTX Post Processing?
Trimble RTX Post-­‐Processing is a post processing service, currently available through the web
application (www.TrimbleRTX.com) which makes use of the Trimble RTX technology to post process
user submitted observation files. Users can simply submit their duel frequency data file on the web
service page and will receive a post processed solution by email.

Where is CenterPoint RTX Post Processing avaliable?
CenterPoint RTX Post Processing is available for data files collected after May 14, 2011 – anywhere in
the world.
Who can use the CenterPoint RTX Post Processing service?
CenterPoint RTX Post Processing is provided as an open service to all users of ‘supported receivers’. For
more information, or to check if your receiver is supported visit
http://trimbleRTX.com/SupportedDevices.aspx.
Is there any requirements of my observation file?
Data files need to follow the following:
• Accepted formats include: RINEX 2 and RINEX 3 data format and in Trimble proprietary data
formats (e.g. DAT, T01, T02 files)
• Data must be a minimum 1 hour in length but cannot exceed 24 hours
• Data files can only be static
• Data files need to contain duel frequency observations (L1/L2)
• Receiver needs to be listed on the supported receiver list
(http://trimblertx.com/SupportedDevices.aspx)
• Data must have been collected after 14 May 2011
What accuracy can I achieve?
The achievable accuracy level of CenterPoint RTX Post Processing can be better than one centimeter in
horizontal and two centimeters in vertical with one day of measurement data. Since the convergence
time of the solution is well below one hour, the delivered positioning accuracy is at 1-­‐2 cm level within
one hour of measurement data or more.
What GNSS satellite systems does the RTX-­‐Post Processing Use
Trimble CenterPoint RTX Post Processing service uses reference data which tracks the GPS, GLONASS
and QZSS satellite systems. QZSS satellite system support is new to RTX technology and enables a
quicker converged solution and higher accuracy positioning results.
What are the supported coordinate sytems?
Trimble RTX corrected positions are originally derived in ITRF2008 (current epoch), however it has been
identified that users often need their data in different reference frame. Trimble CenterPoint RTX Post
Processing service therefore offers many different reference frames that their data files can be
transformed into. The reference frames currently supported include:
• ITRF 1988 to ITRF 2008
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• NAD83, NAD83-­‐CSRS, NAD83-­‐CORS96, NAD83-­‐2011, NAD83-­‐MA11, NAD83-­‐PA11
• ETRS89, ETRF2000-­‐R05
• GDA94
• SIRGAS2000, SIRGAS95, SIRGAS-­‐CON
When should I use the tectonic plates option?
If individual station velocities are unknown and the user desires to determine a position on a specific
tectonic plate the post processing service allows transforming the ITRF2008 position to another frame
with a different reference epoch and on a selected tectonic plate. The service uses plate rotations
provided by Altamini (2007) and Bird (2003). The following tectonic plates are supported: Africa,
Amurian, Antarctica, Arabia, Australia, Caribbean, Cocos, Eurasia, India, Juan de Fuca, Nazca, North
America, Nubia, Okhotsk, Pacific, Philippine, Rivera, Scotia, South America, South Bismarck, Somalia,
Yangtze.
What accuracy can I achieve?
The achievable accuracy level of Trimble CenterPoint RTX post processing can be better than one
centimeter in horizontal and two centimeters in vertical with one day of measurement data. Since the
convergence time of the solution is well below one hour, the delivered positioning accuracy is at 1-­‐2 cm
level within one hour of measurement data or more.
What GNSS satellite systems does the RTX-­‐Post Processing Use
Trimble CenterPoint RTX Post Processing service uses reference data which tracks the GPS, GLONASS
and QZSS satellite systems.
What is the recommended length of a data session?
The achievable accuracy is very closely correlated to the length of the occupation length in the
observation file. It is not recommended to have data sets that are shorter than one hour in length and
the system will not accept observation files that are longer than twenty four hours in length.
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How does the ionosphere affect the RTX positioning?
GNSS signals are travelling through a part of the earth’s atmosphere called the ionosphere. When the
signal is travelling through the ionosphere, refraction, or bending of the wave, occurs. The level of
ionospheric activity is dependent on:
§ Solar activity; it is highest at solar maxima during an eleven year solar cycle; the next solar
maximum will be expected to be reached during 2013
§ Time of day (highest at local noon)
§ Season (highest at equinoxes – March/September)
The ionospheric effect is frequency dependent, i.e. under normal conditions, dual-­‐frequency (L1 and L2)
code / carrier phase observations can be used to essentially remove ionospheric errors. This is what is
done in RTX positioning, i.e. the position estimate is independent of the level of ionospheric effects as
long as no ionospheric scintillation is occurring.
Under extreme conditions, ionosphere can become highly stratified (irregular distribution of charged
particles) leading to GNSS signal scintillation. Ionospheric scintillation involves fluctuation in the phase
and amplitude of GNSS signals. In extreme cases, scintillation can cause loss of signal tracking (i.e. cycle
slips). It is important to note that the effects of scintillation are not removed by dual-­‐frequency
observations. Trimble has setup a global ionospheric scintillation sounding network, which detects
scintillation effects and is able to give up to date warning information on scintillation effects in different
parts of the world.
Typically scintillation occurs in equatorial regions after sunset for several hours. In polar regions,
scintillation can occur at any time. Mid-­‐latitude regions are sometimes affected by Travelling
Ionospheric Disturbances (TIDs).
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