Vicmap Position - GPSnet

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					Vicmap Position - GPSnet™
GPSnet Rebroadcast Model (GRM) - FAQs
The following FAQs focus on          Operating Reference Stations           approximate coordinates of their
                                     (CORS).                                desired areas of operation for
how to access GPSnet using a                                                local broadcast coverage. The
Rebroadcast Model that can be        How does the GRM work?                 GPSnet system software supplier
applied to Precision Agriculture     The diagram below helps explain        recommends that GPSnet users
                                     the elements that make the GRM         operate within a 5km radius
and other applications.                                                     (~2,500ha) of the user’s nominated
                                                                            VRS location.
                                     GRM requires a local data
What is the GPSnet                   modem/radio connected to the           The VRS solution models the
Rebroadcast Model (GRM)?             internet linking to GPSnet services.   geometric and atmospheric errors
Typically, GPSnet users (such as     The internet can be accessed via       over the area of operation to
surveyors) connect to GPSnet via     high speed options such as ADSL        enable uniform position and
the internet using mobile phone      broadband or Very Small Aperture       navigation solutions with +/-2cm
technology. However mobile           Terminal (VSAT) satellite services     horizontal accuracy over GPSnet’s
phone coverage may not be            (if no ADSL broadband is               NRTK service area.
available in some areas to support   available).
                                                                            VRS solutions can be broadcast
applications such as precision
                                     Free GNSS Internet Radio software      anywhere within the user’s local
agriculture. This led to the
                                     running on the user’s personal         radio range and can be quickly
development of the GPSnet
                                     computer controls GPSnet               altered to suit the desired area of
Rebroadcast Model or GRM.
                                     correction signals sent to a local     operations.
The GRM enables users to be          radio for rebroadcast.
                                                                            Typically, in a VRS solution a
supplied with high accuracy
                                     The user can then create and           roving GNSS/GPS receiver will
Virtual Reference Station (VRS)
                                     control VRS signal corrections in      automatically update the VRS
corrections from GPSnet. The
                                     their locality.                        position every time a user moves
corrections are based on a
                                                                            5km. However as the GRM does
Network Real Time Kinematic          What area coverage does the            not support a two way
(NRTK) solution derived from
                                     GRM provide?                           communication link with the
multiple GPSnet Continuously
                                     The GRM allows users to input          roving GNSS receiver (i.e. atop a
tractor) and GPSnet, the VRS
position coordinates need to be
                                     Is GPSnet compatible with my         What is the pricing schedule
manually updated in GNSS
                                     GNSS receiver?                       for precision farmers?
Internet Radio. This process can
be streamlined by simply pre-        GPSnet supports GNSS receivers       DSE manages and operates the
programming VRS position             that can process RTCM 3, the         GPSnet infrastructure while the
coordinates to suit particular       international GNSS data format.      private sector is encouraged to
areas of operation. The user                                              market to end users through a
                                     A precision agriculture trial
inputs the coordinates of the VRS                                         Value Added Reseller (VAR)
                                     conducted in 2007 showed that
position into the computer that                                           arrangement. Accordingly pricing
                                     existing auto guidance systems
apply to the paddocks in location                                         will vary depending on your
                                     can successfully adapted to
A.                                                                        preferred VAR.
                                     process GPSnet corrections. DSE
For paddocks in location B, for      is actively working with GNSS        Current GPSnet VARs in
example 15km away from location      equipment suppliers to enable a      alphabetical order include:
A, a second pre-selected VRS         broader adoption of GPSnet
                                                                          C.R.Kennedy &           (03)9823
position can be typed in. This       services.                            Company Pty Ltd         1504
allows a user to shift the                                                (Leica)
                                     For example:
navigation solution to meet a                                             Laser Beams (Topcon)    (03)9706
                                     • Suppliers and users of John                                9966
user’s need for a particular farm
                                       Deere equipment;                   Lightwave               (03)9720
enterprise.                                                               Technology (Sokkia)     6222
                                     • Leica MojoRTK system;              Ultimate Positioning    (03)9563
The GRM solution can be
                                                                          (Trimble)               0088
programmed into any location         • CTF solutions; and,
within the user’s radio operating                                         How do I set up the GRM at
range which can be extended          • Ag-co (contact James Lang); and
                                       Massey Ferguson (contact Hilton
                                                                          my farm?
using radio repeaters.
                                       Ford) through a GPSnet             Your VAR should give you a step
                                                                          by step guide on how to set up
What effect does a radio               demonstration license.
                                                                          your system to allow for GPSnet
repeater have on the GPSnet          As GNSS/GPS CORS networks            corrections and a basic overview is
signal?                                                                   given below:
                                     become increasingly available
                                                                          1. Contact a VAR to gain access to
A repeater typically adds 0.2 sec    across Victoria (and elsewhere)         GPSnet licence;
delay to the GPSnet signal           users should encourage their         2. Connect ADSL broadband or
transmission. Signal transmission    preferred GNSS equipment                satellite internet to your PC;
delays should be minimised to        supplier to support CORS-ready
ensure valid GNSS solutions.         receivers that adopt international
                                     signal formats such as RTCM 3.
How do I broadcast multiple
VRS solutions using GRM?
Users are able to broadcast
multiple GRM solutions, provided
that the data transmitted via the
radio is sent over two different

Computers typically have multiple
COM ports allowing the GNSS
Internet Radio software to run two
or more sessions, generating
multiple VRS solutions from the
one internet connection.

This enables multiple tractors to
operate simultaneously in
different paddocks, using multiple
radio frequencies.
3. Download GNSS Internet Radio             • GNSS Internet Radio software;       valley. The GRM allows users to
   software free                              and,                                cover the region effectively using
                                                                                  dedicated radio solutions.
   m - 680kb);                              • High speed internet connectivity
4. Link a suitable radio to your              (i.e. satellite, ADSL). Dial up     Should I purchase a dual
   computer and mount a radio
                                              speeds are not supported.           constellation receiver?
   antenna in a location where the
   signal can reach the area of                                                   Contact your GNSS equipment
                                            Why should farmers adopt the          supplier for detailed information
5. Mount a suitable dual frequency          GRM?                                  regarding dual constellation
   GNSS receiver/ antenna and               GPSnet is the ultimate positioning    receivers. GPSnet is working
   radio receiver/antenna on your                                                 towards developing a dual
                                            and navigation infrastructure.
   tractor or other farm
   equipment.                                                                     constellation network. For details
                                            Key GPSnet benefits are:
6. Input the coordinates where you                                                of GPSnet CORS view
   would like the VRS to operate.           • network operated, managed and and
                                              regulated by spatial industry       go to GPSnet Logon and Base
Now you are ready to use GPSnet!                                                  Station Site Details.
                                              professionals to international
What is the typical ongoing                                                       What is the difference
internet connectivity cost and              • improved reliability - CORS are
                                                                                  between one or more
how much bandwidth does                       continuously monitored;
                                                                                  individual RTK Base Stations
GPSnet use?                                 • a homogeneous solution (user        and a CORS RTK network?
Bandwidth of the GPSnet data                  accuracy does not degrade with      A CORS network uses strategically
stream is minimal and costs vary              increasing range from               located GNSS reference stations to
depending on the data packages                contributing CORS);                 support a wide range of users and
                                            • satellite corrections supplied to   an authoritative CORS network
Importantly when choosing a data              users conforming with national      such as GPSnet, physically realises
package with your Internet Service            and state datum GDA94; and          the State legal surveying and
provider (ISP) it is important to                                                 mapping datum.
                                            • no need to own and operate
investigate CIR (Committed
                                              individual physical GNSS/GPS        CORS networks stream raw GNSS
Information Rate) whereby you are
                                              base stations.                      reference station data to a central
guaranteed a bandwidth rate
                                                                                  server that models satellite errors
independent of the number of                Farming enterprises over large        measured across regions and
other ISP users in the area. GPSnet         areas can be conveniently             monitors data quality, both at
depends on a continuous stream              managed using GRM with the            individual GNSS reference stations
of information therefore a reliable         ability to generate multiple GNSS     and across the network. Network
internet connection is important.           network solutions.

What do I need for GRM?                     Some GPSnet users experience
                                            mobile phone coverage shadows
• Dual frequency RTK GNSS
                                            created by the surrounding
  receiver and antenna capable of
                                            environment, for instance in a
  processing the RTCM 3 data

• Pair of data radios able to
  broadcast over the area of
  operation. Your radio supplier
  will recommend the best
  transmission frequency (ie
  UHF/VHF) and power for your

• Personal computer with modem
  and a radio comms port;

• GPSnet licence obtainable
  through a GPSnet VAR;

• Internet Service Provider (ISP);
RTK (NRTK) corrections are then       achieve this goal.
sent to multiple users consistently
                                      DSE are encouraging GNSS
delivering accurate navigation and
                                      equipment suppliers to provide
positioning year after year.
                                      CORS ready equipment to users.
Individual or arrays (often
erroneously referred to as            Key abbreviations and links:
networks) of RTK GNSS/GPS base        RTCM 3.0 - Radio Technical
stations typically:                   Commission for Maritime Services
                                      3.0 parameters.
•   support a restricted number
    of users;                         VAR – Value Added Reseller
•   do not model satellite errors     VRS – Virtual Reference Station
    to ensure consistent user
                                      VSAT - Very Small Aperture
•   are not remotely monitored
                                      Please visit
    for data quality/function;
                                      for GPSnet staff contact details
•   are not synchronised with an      and further information.
    official datum.

What is the future direction of
GPSnet and GRM?
DSE aims to extend the GPSnet +/-
2cm NRTK coverage state-wide
and will continue to work with
industry and other partners to

GPSnet Rebroadcast Model (GRM)
Illustrating how a farmer with many separated paddocks
can operate using the GRM.

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