Topcon America 841221 User Manual
DRAFAFT
Introduction
The GMS-2Pro receiver is a single-frequency, GPS+GLONASS L1
receiver and hand-held controller built to be the most advanced,
compact, and portable receiver for the GIS surveying market. An
integrated electronic compass and digital camera make the GMS-2Pro
an all-purpose, GIS field mapping unit.
The GMS-2Pro receiver is a multi-function, multi-purpose receiver
intended for precision markets. Precision markets means markets for
equipment, subsystems, components and software for surveying,
construction, commercial mapping, civil engineering, precision
agriculture and land-based construction and agriculture machine
control, photogrammetry mapping, hydrographic and any use
reasonably related to the foregoing.
The GMS-2Pro provides the functionality, accuracy, availability, and
integrity needed for fast and easy data collection.
Principles of Operation
Surveying with the right GPS receiver can provide users accurate and
precise positioning, a requirement for any surveying project.
This section gives an overview of existing and proposed Global
Navigation Satellite Systems (GNSS) and receiver functions to help
you understand and apply basic operating principles, allowing you to
get the most out of your receiver.
GNSS Overview
Currently, the following three global navigation satellite systems
(GNSS) offer line-of-site radio navigation and positioning, velocity,
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Introduction
and time services on a global, all-weather, 24-hour scale to any user
equipped with a GNSS tracking receiver on or near the Earth’s
surface:
• GPS – the Global Positioning System maintained and operated by
the United States Department of Defense. For information on the
status of this system, visit the US Naval Observatory website
(http://tycho.usno.navy.mil/) or the US Coast Guard website
(http://www.navcen.uscg.gov/).
• GLONASS – the Global Navigation Satellite System maintained
and operated by the Russian Federation Ministry of Defense. For
information on the status of this system, visit the Ministry of
Defense website (http://www.glonass-center.ru/frame_e.html).
• GALILEO – an upcoming global positioning system maintained
and operated by Galileo Industries, a joint venture of several
European space agencies working closely with the European
Space Agency. Unlike GPS and GLONASS, this is a civil
endeavor and is currently in the development and validation stage.
For information on the status of this system, visit the Galileo
Industries website (http://www.galileo-industries.net).
Despite numerous technical differences in the implementation of
these systems, satellite positioning systems have three essential
components:
• Space – GPS, GLONASS, and GALILEO satellites orbit
approximately 12,000 nautical miles above Earth and are
equipped with a clock and radio. These satellites broadcast digital
information (ephemerides, almanacs, time&frequency corrections,
etc.).
• Control – Ground stations located around the Earth that monitor
the satellites and upload data, including clock corrections and new
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ephemerides (satellite positions as a function of time), to ensure
the satellites transmit data properly.
• User – The community and military that use GNSS receivers and
the corresponding satellites to calculate positions.
Calculating Absolute Positions
When calculating an absolute position, a stationary or moving
receiver determines its three-dimensional position with respect to the
origin of an Earth-Center Earth-Fixed coordinate system. To calculate
this position, the receiver measures the distance (called
pseudo-ranges) between it and at least four satellites. The measured
pseudo-ranges are corrected for clock differences (receiver and
satellites) and signal propagation delays due to atmospheric effects.
The positions of the satellites are computed from the ephemeris data
transmitted to the receiver in navigation messages. When using a
single satellite system, the minimum number of satellites needed to
compute a position is four. In a mixed satellite scenario (GPS,
GLONASS, GALILEO), the receiver must lock onto at least five
satellites to obtain an absolute position.
To provide fault tolerance using only GPS or only GLONASS, the
receiver must lock onto a fifth satellite. Six satellites will provide fault
tolerance in mixed scenarios.
Calculating Differential Positions
DGPS, or Differential GPS, typically uses the measurements from two
or more remote receivers to calculate the difference (corrections)
between measurements, thus providing more accurate position
solutions.
With DGPS, one receiver is placed at a known, surveyed location and
is referred to as the reference receiver or base station. Another
receiver is placed at an unknown, location and is referred to as the
remote receiver or rover. The reference station collects the range
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measurements from each GPS satellite in view and forms the
differences (corrections) between the calculated distance to the
satellites and the measured pseudo-ranges to the satellites.
These corrections are then built up to the industry standard (RTCM or
various proprietary standards) established for transmitting differential
corrections and broadcast to the remote receiver(s) using a data
communication link. The remote receiver applies the transmitted
DGPS corrections to its range measurements of the same satellites.
Using this technique, the spatially correlated errors—such as satellite
orbital errors, ionospheric errors, and tropospheric errors—can be
significantly reduced, thus improving the position solution accuracy
of the GPS.
A number of differential positioning implementations exist, including
post-processing surveying, real-time kinematic surveying, maritime
radio beacons, geostationary satellites (as with the OmniSTAR
service), and the wide area augmentation system (WAAS) service.
The real-time kinematic (RTK) method is the most precise method of
real-time surveying. RTK requires at least two receivers collecting
navigation data and communication data link between the receivers.
One of the receivers is usually at a known location (Base) and the
other is at an unknown location (Rover). The Base receiver collects
carrier phase measurements, generates RTK corrections, and sends
this data to the Rover receiver. The Rover processes this transmitted
data with its own carrier phase observations to compute its relative
position with high accuracy, achieving an RTK accuracy of up to 1 cm
horizontal and 1.5 cm vertical.
Essential Components for Quality Surveying
Achieving quality position results requires the following elements:
• Accuracy – The accuracy of a position primarily depends upon the
satellite geometry (Geometric Dilution of Precision, or GDOP)
and the measurement (ranging) errors.
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– Differential positioning (DGPS and RTK) strongly mitigates
atmospheric and orbital errors, and counteracts Selective
Availability (SA) signals the US Department of Defense
transmits with GPS signals.
– The more satellites in view, the stronger the signal, the lower
the DOP number, the higher positioning accuracy.
• Availability – The availability of satellites affects the calculation
of valid positions. The more visible satellites available, the more
valid and accurate the position. Natural and man-made objects can
block, interrupt, and distort signals, lowering the number of
available satellites and adversely affecting signal reception.
• Integrity – Fault tolerance allows a position to have greater
integrity, increasing accuracy. Several factors combine to provide
fault tolerance, including:
– Receiver Autonomous Integrity Monitoring (RAIM) detects
faulty GPS and GLONASS satellites and removes them from
the position calculation.
– Five or more visible satellites for only GPS or only
GLONASS; six or more satellites for mixed scenarios.
– Wide Area Augmentation Systems (WAAS, EGNOS, etc.)
creates and transmit, along with DGPS corrections, data
integrity information (for example, satellite health warnings).
– Current ephemerides and almanacs.
Conclusion
This overview simply outlines the basics of satellite positioning. For
more detailed information, visit the TPS website.
GMS-2Pro Overview
The GMS-2 is a fully integrated hand-held controller and GPS+
receiver. Included in the system is an electronic compass and digital
camera.
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Introduction
The hand-held controller component of the GMS-2Pro
includes the Windows® CE operating system and color LCD touch
screen. Integrated Bluetooth® wireless technology allows this system
to be a cable-free controller/receiver for maximum portability. The
rugged casing is durable and built for rugged use.
As a field controller, the GMS-2Pro can run a full suite of field
software for working with total stations and RTK GPS systems.
The GPS+ receiver component of the GMS-2
can receive and process GPS+GLONASS L1 signals improving the
accuracy of your survey points and positions. The GPS+ features of
the receiver combine to provide a positioning system accurate for any
survey. Several other features, including multipath mitigation, provide
under-canopy and low signal strength reception.
When power is turned on and the receiver self-test completes, the
receiver’s 50 channels initialize and begin tracking visible satellites.
Each of the receiver’s channels can be used to track any one of the
GPS or GLONASS signals. The number of channels available allows
the receiver to track all visible GPS satellites at any time and location.
An internal GPS antenna equipped with a low noise amplifier (LNA)
and the receiver’s radio frequency (RF) device are connected with a
coaxial cable. The wide-band signal received is down-converted,
filtered, digitized, and assigned to different channels. The receiver
processor controls the process of signal tracking.
Once the signal is locked in the channel, it is demodulated and
necessary signal parameters (carrier and code phases) are measured.
Also, broadcast navigation data are retrieved from the navigation
frame.
After the receiver locks on to four or more satellites, it is possible to
solve the so-called “absolute positioning problem” and compute the
receiver’s coordinates (in WGS-84) and the time offset between the
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receiver clock and GPS time. All this information can be stored in the
the optional SD card and internal flash memory, then processed using
a post-processing software package.
Capabilities of the GMS-2Pro receiver include:
• Multipath reduction
• Wide area augmentation system (WAAS)
• Single-frequency static, kinematic, and differential GPS (DGPS)
survey modes
• Setting different mask angles
• Setting different survey parameters
The integrated 1.3 megapixel camera
is used taking pictures of surveyed objects or survey sites.
Getting Acquainted with the GMS-2Pro
The GMS-2Pro is an integrated field controller and 50-channel GPS
receiver with an internal electronic compass and digital camera. USB
and serial ports, along with Bluetooth® wireless technology provide
communication paths with other devices. An external GPS antenna
connector allows an optional PG-A5 antenna to be connected for
centimeter-level surveys.
The standard GMS-2Pro package contains the following items:
• GMS-2Pro integrated receiver/controller activated for GPS L1
signals
• Handstrap and soft case
• USB cable and power converter/adapter cable
• BTManager and GMS Tools factory-installed software
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For more details on accessories and options available for the GMS-2,
contact your local Topcon dealer.
Rechargeable and Backup Batteries
The GMS-2 comes equipped with a rechargeable battery (GMS-2Pro
Battery) for powering the unit. The battery can be charged in the unit
or in an optional battery charger. A backup battery is also located in
the battery pocket and the unit’s serial number is located under the
battery.
The battery provides seven hours of operation, depending on the mode
of the receiver. Under normal conditions, the backup battery provides
eight to ten years of power backup for data and system integrity.
Battery
Serial
Number
Backup
Battery
Figure 1-2. GMS-2Pro Battery
GMS-2Pro Front
The front of the GMS-2Prois the primary interface with its
components and installed software.
• The internal GPS antenna detects signals from GPS+ satellites
and sends them to the GPS receiver board for processing.
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• The display screen and touch panel provides a graphical and
tactile user interface for the unit.
• The power button turns the receiver on and off.
• The ESC (escape) button exits from the current screen or
function.
• The ENT (enter) button applies settings, numerical values, and
records points (depending on the settings of internal software).
Pressing this button for one second activates the controller’s
Windows Start menu.
• The Bluetooth LED indicates the level of activity at the
Bluetooth wireless technology module:
– Solid blue light: the module is on and a connection has been
established.
– No light: the module is off.
• The charging LED indicates the level of charge in the battery:
– Green: battery has a full charge.
– Red: battery is charging.
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– Red blink: charging error.
Internal GPS
Antenna Cover
Display and
Touch Screen
Bluetooth
LED
Escape
Button
Speaker
Figure 1-3. GMS-2 Front
Power
Button
Enter
Button
Charging LED
Microphone
GMS-2Pro Back
The back of the GMS-2Pro holds the stylus used for tapping on the
display screen. An elastic strap provides comfortable security while
using the GMS-2Pro. A cover accesses the rechargeable battery and
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