NTRIP – Purpose and Perspectives

Christian WaeseFederal Agency for Cartography and Geodesy(Bundesamt für Kartographie und Geodäsie, BKG)

Frankfurt am Main, Germany

2nd Trimble GPSNet Users Seminar, 30 - 31 May 2006, Munich

1. Introduction – What is NTRIP?

2. Free NTRIP Software Tools

3. Benefits of NTRIP usage within an RTK network

4. Data Policy Recommendations

5. NTRIP 2.0

6. Summary

Overview

NNetworked etworked TTransport of ransport of RRTCMTCMvia via IInternet nternet PProtocolrotocol

• 2004: NTRIP becomes RTCM (Radio Technical Commision for Maritime Services) SC104 Standard

• Based on HTTP/1.1 (port 80 or 8080) and Internet Radio technology

• Supports mass usage:hundreds of data streams may be transmitted to up to thousand users

• Any kind of GNSS data may be transmitted:RTCM / raw data, or any other streamed data (iono-models, ephemeris, …);

• Only requirement:data stream with ~ 0.5 to 5 kbit/s bandwidth

1. Introduction – What is NTRIP?

1. Introduction – What is NTRIP?

GNSS Internet Radio / IP-Streaming

Server ClientSplitterCaster

NTRIP system components

• Supports wireless Internet: GSM, GPRS, EDGE, UMTS,…• Access control to data streams is possible

→ enables billing• NTRIP is an industry standard

→ many GNSS hard- and software developers haveimplemented NTRIP into their products, e.g.

- Trimble GPSNet, NetR5 (server&client), …- Leica GPS Spider, GPS1200 Rover, …- Geo++ GNSmart, GNCaster, …- Topcon TopSURV, …- Thales NTRIP client, …- Sokkia GSR2700 Rover, …- EuroNav EuroNet, …- …

1. Introduction – What is NTRIP?

NTRIP hard- and software

1. Introduction – What is NTRIP?

2. Free NTRIP Software Tools

NtripClient• Windows: GNSS Internet Radio• Windows: CE & PocketPC 2003: GNSS Internet Radio• Linux: Plain Example Program, GNU GPL• Linux: Perl NtripClient, GNU GPL• Palm OS: Demo Example Program

NtripServer• Windows: Reading from Serial Port• Windows: Command line version, reading from IP address/port• Linux: Reading SISNeT, TCP/UDP Port, Serial Port, NtripCaster, GNU GPL• Linux: Perl NtripServer, Reading from Standard Input, GNU GPL

NtripDecoder, Converter, etc.• Windows: GnssSurfer, Client & Server & RTCM 2.x Decoder• Windows: RTCM 2.x DGPS/RTK Decoder, reading from TCP/IP Port• Linux: Stand-alone RTCM 2.x RTK Decoder, reading from Std. Input, GNU GPL• Linux: Multi-Stream Client and RTCM 2.x to RINEX Converter, GNU GPL• Linux: Client and RTCM 3 to RINEX Converter, GNU GPL

http://igs.bkg.bund.de/index_ntrip_down.htm

2. BKG’s NTRIP Software Tools

- one example: BKG’s NtripClient

NTRIP features meta data!(unlike GSM)

2. BKG’s NTRIP Software Tools

- one example: BKG’s NtripClient (cont’d)

2. BKG’s NTRIP Software Tools

- Meta data: BKG’s www.euref-ip.net Sourcetable

For the network operator:

• only one TCP port has to be opened for an unlimitednumber of incoming NTRIP data streams (usually port 80)

3. Benefits of NTRIP usage within an RTK network

For the network operator (continued):

• only one TCP port has to be opened for an unlimited number ofuser requests for correction data streams,usually ports 80 and 8080 are not blocked by firewalls and proxy servers

e.g.: http://www.euref-ip.net:80/ → port 80 or 2101

• there is no direct contact between reference station(NtripServer)and customer(NtripClient), all streams are administeredvia the NtripCaster → safe data flow

• no dedicated hardware for sending RTCM corrections needede.g. no GSM → no access server required

• easy user accounting via user name and password

3. Benefits of NTRIP usage within an RTK network

3. Benefits of NTRIP usage within an RTK network

For the network customer:

• large number of NTRIP hard- and software, most of latest GNSS hardware is NTRIP-capable→ no extra hardware for receiving RTCM corrections

• low costs of data transmission with, e.g., GPRSor other packet- (NOT time-)based mobile communication

• low costs of data transmission with RTCM 3.0 due tohigh compression rate of DGNSS data

4. Data Policy Recommendations

RTK network operator may consider participation in regional or global projects like EUREF or IGS providing free access to at least one real-time data stream to:

• Align the local network to the respective regional or globalreference frame, e.g. ETRF / ITRF

• Become a part of global GNSS activities that lead to:- a more stable reference frame realisation- more accurate ephemeris and clock data- support the development of upcoming global real-timeproducts

This does not contradict commercial interests, as:- access may be controlled by user authentication,- access may be disrupted at any time

4. Data Policy Recommendations

Benefits of the availability of one unrestricted stream per network:

• every EUREF/IGS station is intensely monitored → reference in case of unstable stations within the network

• exchange of real-time data at network boundaries enablingseamless DGPS/RTK operation from one network to the other

Best suited data format: RTCM 3.0 including raw observations- contains the complete set of information collected at thereference station → best information for global R&D purposes

- alternative in case of commercial concerns: raw data

Post-Processing

Real-Time

ASCOSGREFEUREFIGS

AligningRTK Net

to ETRF/ITRFin Real-Time

Global HubContinental HubsRegional Hubs

Upcoming EUREF & IGS EffortsBroadcast of RTCM 3.0 via NTRIP

World-wide data streams via NTRIP

World-wide stations via NTRIP, www.igs-ip.net

5. NTRIP 2.0

Deficiencies of NTRIP Version 1.0:

• NTRIP 1.0 is not fully HTTP/1.1 compatible:

- “SOURCE” method at server-caster communication- “GET” method at client-caster communication

uses incorrect response definition (media types, caching)- special content-length identifier

→ Internet security software may block communication

• Sourcetable of NtripCaster may be too long for many mobile clients’ display or memory

5. NTRIP 2.0

Main features of NTRIP Version 2.0:

• Full HTTP/1.1 compatibility

- replace “SOURCE” directive by “POST”- use Mean Greenwich Time (GMT) for all time stamps- apply “chunked transfer encoding”, no need for extra

field length indicator→ solves problems at proxy servers / firewalls / …

• UDP unicast support

5. NTRIP 2.0

Main features of NTRIP Version 2.0:

• intention to filter the sourcetable according to the client’s needs→ solves problem with limited display or memory→ minimises transmission cost and time

6. Summary

• NTRIP is an RTCM standard to transport GNSS data using mobile Internet connections

• It has been implemented in most of latest GNSS hard- and software, including all relevant Trimble products

• All communication works on one single TCP port (80)• Best data format to be used for correction data transmission

is RTCM 3.0 (high compression)• Every network operator should provide one free data stream

to support global non-profit GNSS R&D initiatives• Deficiencies of NTRIP 1.0 will be solved with upcoming new

version 2.0

Thank you for your attention!christian.waese@bkg.bund.de

www.euref-ip.net/homewww.igs-ip.net/home