ipexSR
- a GNSS Software
Receiver
The receiver
provides two positioning modes: single point positioning and real-time kinematic
(RTK) positioning. Both positioning algorithms accept as input data code
and pseudorange measurements which can taken from the tracking module (real-time)
or
from
RINEX data. Satellite orbit and clock parameters are taken
from SP3 files (precise ephemeredes), from RINEX navigation files or from
the decoded navigation data message.
Single
Point Positioning
The single
point positioning is based on a least squares adjustment of the measured
pseudoranges. Unknown parameters are receiver position, clock error and
ionospheric delays. The image below shows the dialog to configure the single
point positioning algorithm.
The
accuracy of the single point positioning depends on satellite orbit and clock
errors, atmospheric errors, code multipath errors and thermal noise
errors.
Validation of the receiver was
performed by connecting it to a GPS signal simulator where all error sources,
with the exception of thermal noise, can be switched off. In this case the
horizontal accuracy is in the sub-meter level even for a low-bandwidth (i.e.
low-cost) GPS front end and only by using code pseudorange
measurements.
Real-Time
Kinematic Positioning (L1 C/A code and L2 civil signal)
The RTK
positioning module of the
ipexSR is currently under development and is based on the LAMBDA method
to resolve carrier phase integer ambiguities. The positioning module accepts
as input code and phase pseudorange measurements on L1 and L2. The GPS C/A
code and the GPS L2 civil signal (CS) are used. Data from the reference station
is broadcast via the internet (TCP/IP). As a reference station a commercial
GPS receiver can be used as well as second ipexSR.
The RTK module can also work in post-processing accepting RINEX data as
input.
RTK
positioning achieves an accuracy on the order of a few cm mainly depending
on the distance between the reference station and the rover once the ambiguities
have been fixed. By using the civil signals alone -i.e. without tracking
the GPS P(Y) code with (semi-)codeless techniques- a much simpler and more
robust receiver design can be achieved.
For
more information on RTK positioning click
 here.
Back
|
