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What is a CORS?

Most people are now familiar with the

use of Global Navigation Satellite

Systems (GNSS) like the ones used

for in-car and handheld navigation.

They calculate position using signals

from GNSS, such as the United

States’ Global Positioning System

(GPS), and have an accuracy of

somewhere between a few and a few

hundred metres. This relatively poor

accuracy is the result of minute

errors in the satellite orbits, the

clocks installed in the satellites and

receivers, as well as the tendency for

the earth’s atmosphere to bend or

delay the GNSS radio signal. There

are, however, GNSS receivers used

by surveyors and researchers which

can be used to accurately calculate

position at the centimetre level. To

obtain this accuracy these receivers

need to be able to include

sophisticated error corrections in

their position calculations.

Short for Continuously Operating

Reference Station, a CORS is a high

precision GNSS antenna/receiver set

on a stable monument and

connected to uninterruptable power

supply and secure communication

facilities. Logging position data

continuously, the CORS are used to

generate the information needed by

high precision GNSS receivers for

error corrections in real-time or post

mission.

CORSnet-NSW

DFSI Spatial Services has invested

in rolling out CORS across NSW to

form a network for state-wide precise

positioning. The rollout will reach 200

stations in 2017 including 11 stations

as part of the national AuScope

network.

CORSnet-NSW network as of February 2017

TABLE OF CONTENTS Glossary of Terms.................................................................................................................................... 1

Web Portal Instructions .......................................................................................................................... 2

Logged Out Environment .................................................................................................................... 2

Logged In Environment ....................................................................................................................... 3

Real-time Instructions ............................................................................................................................. 8

Using CORSnet-NSW in Real-time ....................................................................................................... 8

Network Real-time Solutions .............................................................................................................. 8

Mount Points ...................................................................................................................................... 8

Other Features of CORSnet-NSW Real-time services ......................................................................... 9

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GLOSSARY OF TERMS

Term Definition

CMRp Compact Measurement Record plus - A format for real-time data streaming, commonly used in agricultural and construction applications.

CORS Continuously Operating Reference Station - An installation that is precisely located and continuously observing GNSS data. Arrays of CORS are often linked together as part of a network to deliver precise positioning solutions over large areas.

CORSnet NSW The CORS network infrastructure available in NSW from 1 July 2009.

DGNSS Differential GNSS - A basic method of processing GNSS data to achieve sub-metre level accuracies (often referred to as DGPS).

GNSS Global Navigation Satellite System - A global network of satellites producing navigation signals for positioning and navigation applications on earth.

DFSI Department of Finance, Services and Innovation - The NSW Government Agency responsible for delivering CORS to NSW.

MAC Master Auxiliary Concept - A method of NRTK which provides CORS data with correction parameters generated from nearby CORS in order to optimise the solution for a specified location.

Machine Guidance

A system which utilises positioning information to guide or auto-steer machinery along a specified path.

NRTK Network RTK - An enhancement of RTK which utilises data from multiple CORS to provide a uniform level of accuracy across the network.

NTRIP Networked Transport of RTCM via Internet Protocol - A method for streaming RTCM messages over the internet.

RINEX Receiver Independent Exchange - An international standard for the storage of GNSS data.

RTCM The Radio Technical Commission for Maritime Services – An international standard for real-time data streaming of GNSS data.

RTK Real Time Kinematic - A sophisticated method of processing GNSS data to achieve centimetre level accuracies.

SydNET The CORS system offered in NSW prior to 1 July 2009 and as a back-up system until 2 May 2011.

VRS Virtual Reference Station - A method of NRTK which generates virtual data from data collected at nearby CORS for a specified location.

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WEB PORTAL INSTRUCTIONS The webpage for CORSnet-NSW is available at the following URL:

http://corsnet.nsw.gov.au

LOGGED OUT ENVIRONMENT CORS Map

The CORS Map shows a live update of station health for every CORS in the CORSnet-NSW network. Sites in green are healthy, while sites coloured yellow or red are currently unhealthy or offline. You can click on a CORS to display more information.

Login

To login to CORSnet-NSW you are required to enter your organisation name, user name and password. When an account is created for you, this information will be provided through an automated email.

More Information

This link will take you to the CORSnet-NSW information website to access CORS station details and other useful information.

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LOGGED IN ENVIRONMENT Status Messages

Status messages are used to inform users of important information about CORSnet-NSW. Three levels of messages exist: Info, Warning and Alert. These will be highlighted green, yellow and red respectively to indicate the severity of the message. Info messages will be used to inform users of general news and tips for using CORSnet-NSW. Warning messages will be used to inform users of planned maintenance and any issues associated with CORSnet-NSW. Alert messages will be used for major issues and unplanned outages of service. Users are advised to subscribe to the RSS feed to ensure that they keep up to date with the latest information available. This feed can be accessed using various apps on smartphones in the field.

The CORSnet-NSW RSS feed is available at:

http://corsnet.nsw.gov.au/StatusMessageFeed.svc/?

Reference Data Shop

This is where you can access archived GNSS data as RINEX files or alternatively in a number of other formats. The first time you access the Reference Data Shop you will be asked to start a new order. After that you will be given the options of choosing to View/submit order, Add order items or Cancel order. You can also view a list of orders not yet downloaded and already downloaded orders. When ordering data you are given the option of ordering Continuously Operating Reference Station (CORS) data or Virtual Reference Station (VRS) data. CORS data is the data observed at the CORS sites while VRS data is virtual data generated for a user specified location.

When selecting the Reference Stations for which you would like to download data, you can either

select one or many stations from the list or select them by clicking on the map (not yet available).

Once your selection is complete, click Next: Time Selection >> and select the date, start time,

duration and interval. Please note that the time system used is GPS time and not Australian Eastern

Standard Time. You will need to subtract ten hours from Australian Eastern Standard Time (or

eleven hours for Australian Eastern Summer Time) to determine the appropriate GPS time.

Once your Time Selection details are complete click Next: Add to order >>. Here you can either

select to add additional order items through a number of options. Ensure you book the order under

your primary login as real-time logins do not have access to Reference Data Shop data.

Once your order is complete, click Next: Delivery Options >>. You have the choice of downloading

the data in a number of formats. These are RINEX 2.11, RINEX 3.0, DAT, TGD, T01 and T02. While the

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RINEX formats should be recognised by most software packages, the last four options are not

international standards but may be of use to some users.

When your delivery options selection is complete click Next: Generate Data >>. A table indicating

the Processing Status of the order will appear. You can close this screen and the data generation will

still continue. For large orders it may be preferable to return at a later time to retrieve the data once

this generation is completed.

Once the data generation is complete, click on Next: Order Details >>. Here you will see a summary

of the order including the completeness of the data. Select an order item and click on Details to see

further information. Click on Remove to delete an order item from the list. Click on Download to

retrieve the data.

The data will be delivered in a compressed zip file. Within the zip file you will find three RINEX files:

the observation file, GPS navigation file and the GLONASS navigation file. You will also find a text file

which summarises the data ordered including the completeness of the data.

My Account: Personal Data

This link allows you to update your personal details, including address, email addresses, additional email addresses and phone numbers. It is important that this information is kept up to date to ensure you are kept up to date with CORSnet-NSW related information.

My Account: Change Password

This link allows you to change the password for your primary login. It is advisable to regularly change your password for security reasons.

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My Account: Logins

Here you are able to view your primary login and supplementary real-time logins. By clicking on one of the logins you are to change its password. It is advisable to regularly change your password for security reasons.

My Account: Sessions

This link allows you to view your CORSnet-NSW usage history over varying periods of time. Usage history is summarised in terms of total organisation usage, total login usage and total resource usage (e.g. RINEX or real-time).

Active Subscriptions

Click on this link to view your current valid subscriptions. Click on Details to view further information.

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Logout

This link will take you back to the logged out environment home page. Click on Logout once you have completed accessing CORSnet-NSW data and information.

Using Virtual Reference Station (VRS) RINEX

Tips for users:

Use ellipsoidal height. Convert from the Australian Height Datum (AHD71) using AusGeoid09

here.

Data available for 28 days.

Orders take longer to generate than standard CORS RINEX.

Recommended coverage is within the area for Network RTK published on the CORSnet-NSW

coverage map. The latest map is available from spatialservices.finance.nsw.gov.au/corsnet-nsw in

network information.

Achievable accuracy from VRS RINEX is comparable with CORS RINEX files. Users are advised to test

VRS RINEX to determine whether it is appropriate for their application.

Absolute Antenna Models from the International GNSS Service (IGS) should be used for VRS RINEX

and all other data used in post-processing. The nominated physical antenna in the VRS RINEX file is

generally that of the closest CORS. This must be correctly set in your post-processing software.

Site Transformations (or Localisations/Site Calibrations) are still required. Users should always

connect to local survey control to determine the offset from the Survey Control Information

Management System (SCIMS) coordinates.

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Ongoing testing is being performed by DFSI Spatial Services to advise users on the capabilities and

limitations of VRS RINEX.

RSS Feed for CORSnet-NSW Status Messages

You can subscribe to status messages from CORSnet-NSW via RSS Feed. The address of the feed is:

http://corsnet.nsw.gov.au/StatusMessageFeed.svc/

There are several options available to access the feed.

OPTION A – Microsoft Outlook

1. Right click on RSS Feeds on the left hand pane and select Add A New RSS Feed.

2. Enter the address above and click Add.

3. Outlook will ask you to confirm if you want to add the feed. Click Yes.

OPTION B – Web Browser

1. Open the address above in your web browser (tested on IE 8):

2. Click Favourites and then Add to Favourites Bar (make sure the Favourites Bar is displayed)

3. The link will appear in bold when new status messages are available

OPTION C – Download Program

1. Download RSS Reader available through the following link (alternate programs available

online):

http://www.rssreader.com

2. Install RSS Reader and subscribe to the feed address above.

OPTION D – Smart Phone App

1. Download an RSS feed reader application on your smart phone.

Subscribe to the feed address above.

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REAL-TIME INSTRUCTIONS

USING CORSNET-NSW IN REAL-TIME You can find your login details for real-time access on the CORSnet-NSW Web Portal at My Account:

Logins.

Real-time logins are usually in the format <organisation>/<login>. This login will differ from the

username used to log into the CORSnet-NSW Web Portal. The number of real-time logins will

depend on the number of subscriptions available. All passwords are configurable within the

CORSnet-NSW Web Portal.

In order to connect to CORSnet-NSW in real-time you will also need to enter the following

information into your equipment.

Ntripcaster Address: corsnet.nsw.gov.au

Port: 2101

NETWORK REAL-TIME SOLUTIONS Network solutions are being introduced in NSW and the coverage area will be extended as LPI

continues to roll-out CORS across the state and tests the quality of solutions in regional areas. For

those who have not used a network solution before, it will look and feel, in a practical sense, like a

single base solution. Field procedures should remain the same, particularly in relation to performing

site calibrations.

In areas tested to date, network solutions perform as well or better than single base solutions. It is

important to ensure that your equipment settings match the particular mount point you intend to

use.

The current network solution coverage is illustrated on the CORSnet-NSW map

(spatialservices.finance.nsw.gov.au/corsnet-nsw/network_information).

MOUNT POINTS A mount point relates to a real-time data stream option. When connecting to CORSnet-NSW in real-

time, a mount point list is usually generated for a user to select from. The following options are

available:

Single Base mount point (eg CHIP-RTCM3 for Chippendale): This allows a user to specify which CORS

they would like to receive data from.

Nearest Base mount point (eg nearest-RTCM3): This will automatically provide data from the users

closest CORS. An additional Nearest Base mount point is available for legacy precision agriculture

users only (nearest-RTCM2). Users are advised, where possible, to continue to use the RTCM3

format.

VRS Network RTK mount point (eg VRS-RTCM3): This will provide a network RTK data stream in

Virtual Reference Station (VRS) format.

MAC Network RTK mount point (eg MAC-RTCM3): This will provide a network RTK data stream in

Master Auxiliary Concept (MAC) format.

Virtual Base DGPS mount point (eg DGPS-RTCM2): This will provide a sub

metre differential solution optimised for the user’s location.

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CMRp mount points (eg nearest-CMRp, VRS-CMRp): Two additional mount points, which use the

CMR plus format, have been added to the mount point list. These are intended for legacy equipment

in industry groups where CMR plus has been used as a quasi-standard format (such as precision

agriculture). Users are advised, where possible, to continue to use the RTCM3 format.

OTHER FEATURES OF CORSNET-NSW REAL-TIME SERVICES Please be advised that CORSnet-NSW adjusts real-time data so that all CORS antennas are uniformly

described as a null antenna (ADVNULLANTENNA). As such, no base station antenna model needs to

be applied to adjust CORS observations from the Antenna Phase Centre to the Antenna Reference

Point. Users will still need to apply the appropriate absolute antenna model for their rover. All post

process RINEX files and post process files in other formats continue to hold raw data to the Antenna

Phase Centre in line with international standards.

Absolute antenna modelling, instead of relative antenna modelling, is used in for CORSnet-NSW.

These should be the absolute antenna models derived by the International GNSS Service (IGS) and

users are advised to contact their local GNSS supplier for the required information. Users should also

use absolute antenna models when post processing for both the user and CORS antennas. Any mix

of absolute and relative antenna modelling will introduce significant systematic errors.

Contact Details

For more information or assistance please contact CORSnet-NSW Customer Support at:

Phone: 1300 330 233

Email: SS-CORSnetCustomerSupport@finance.nsw.gov.au

Web Portal: http://corsnet.nsw.gov.au

Website: http://spatialservices.finance.nsw.gov.au/corsnet-nsw

Information provided in this document is intended as a guide only and its accuracy is not guaranteed.

CORSnet-NSW Web Portal User Guide Version 2.1, April 2017

© DFSI Spatial Services April 2017