LINZ Develops Real-Time Position Data

Author: Dave Collett
Date: 26 March 2010

LINZ is currently developing real-time provision of position data from a number of its PositioNZ stations. PositioNZ is a country-wide network of 33 continuously operating global navigation satellite system (GNSS) stations.

The new real-time service, PositioNZ-RT, streams data every second. This contrasts with the current system that provides position data recorded every 30 seconds in hourly and daily files. The new service means you can undertake surveys (and connect to the datum) in real-time using data from the PositioNZ network. You don't have to wait and post-process your data as you have in the past.

We've been trialling this service on a limited basis for a couple of years, and thought it was time to open it up to everyone. We're streaming from about two-thirds of the network at the moment, but plan to upgrade the entire network to real-time capability by mid-2011.

We're also working on giving users information about the quality and continuity of the real-time data provided through PositioNZ-RT.

The upgrade follows an economics report (PDF 97KB) released last year, which estimated real-time GNSS data could benefit the New Zealand economy in the tens of millions of dollars over the next decade. Some industries that could benefit include surveying, infrastructure development, construction and agriculture.

You might also find interesting a presentation on the Role of the Private and Public Sectors in the Development of a National CORS Network for New Zealand (PDF 3.4MB). This was given at the New Zealand Institute of Surveyors Conference late last year. It sets out how LINZ is trying to work with other public agencies, as well as the private sector, to realise the biggest gains for New Zealand from position technology.

You can use PositioNZ-RT data how you wish, including the selling of value-added products. It is possible to use data from a single station for differential GPS (DGPS) and real-time kinematic (RTK) purposes. If you have the right software and inclination, you could generate Network-RTK solutions using the data streams (possibly combined with data from your own stations).

Getting connected

PositioNZ-RT data is being broadcast using NTRIP (Networked Transport of RTCM via Internet Protocol), so to access the data streams you need to have an NTRIP client program. A list of free and commercial NTRIP client programs can be found at the BKG website.

You can access PositioNZ-RT from any internet-enabled device, such as a desktop PC, laptop or PDA. A common way to connect is by using an internet-enabled mobile phone to transmit data, via Bluetooth, to an NTRIP client embedded in a GNSS receiver. You can even connect to the streams via the internet and broadcast them back out via your own radio to your rover. To set up your receiver to get the data, contact your equipment manufacturer.

For full connection details, see the PositoNZ-RT page on the LINZ website.

Getting reliable communications out from some sites can be difficult due to the nature of some of our site locations. Some sites use long radio links and some also use satellite communications. This can add to the latency of the signal - the time it takes the data to reach our data-management centre and be broadcast over the internet. We're working to upgrade these links, so they will improve, and new sites will come online as this is done.

More information & feedback

For more information and examples of similar real-time data services, visit:

• Real-time International GNSS Service (RTIGS) - for an example of a real-time IGS pilot project.
• NTRIP - for more information on real-time GNSS streaming dissemination techniques.
• rtcm-ntrip-org - for other NTRIP broadcaster implementations.

We want the PositoNZ-RT service to deliver the most value it can, so make sure you give us your feedback on the service. In particular, we're interested in:

• what PositioNZ-RT data streams you're accessing
• how often you're accessing them
• what uses you're putting the data to
• any problems you encounter.

Let us know what you think.

Dave Collett

Geodetic Surveyor
Land Information New Zealand