Novatel OM-20000053 Rev 2 4.4 RINEX FORMAT

4 Message Formats

MiLLennium GPSCard SW Version 4.503/4.52 Command Descriptions Manual Rev 2 57

receiving pseudorange and carrier phase data via CMR messages (versions 1.0, 2.0 or 3.0) from a non-NovAtel

base-station receiver. The MiLLennium can also transmit CMR messages (version 3.0). The station ID, see Page

100, must be ≤ 31 when transmitting CMR corrections.

NOTE: No guarantee is made that the MiLLennium will meet its performance specifications if non-NovAtel

equipment is used.

To enable receiving CMR messages, follow these steps:

1. Issue the COMn command to the rover receiver to set its serial port parameters to the proper bit rate, parity,

etc. This command is described in detail on Page 86.

2. Issue the “ACCEPT COMn CMR” command to the rover receiver, where “COMn” refers to either the COM1

or COM2 serial port that is connected to the data link.

Assuming that the base station is transmitting valid data, your rover receiver will now begin to operate in RT-2 or

RT-20 mode. To send CMR messages, do the following:

Periodically transmit two CMR messages at the reference station (the station ID, see Page 100, must be ≤ 31):-

•A CMROBS message contains reference station satellite observation information, and

should be sent once every 1 or 2 seconds.

•A CMRREF message contains reference station position information, and should be sent

once every 10 seconds.

In addition to the logs which you can use to output the rover’s position (e.g. POSA/B, PRTKA/B, RTKA/B), the

baseline (BSLA/B), and the reference station’s position and health (RPSA/B), you can also monitor the status of

the incoming CMR messages using the CDSA/B (Communication and Differential Decode Status) log. See Page

146 for a complete description of the CDSA/B log and its arguments.

4.4 RINEX FORMAT

The Receiver-Independent Exchange (RINEX) format is a broadly-accepted, receiver-independent format for

storing GPS data. It features a non-proprietary ASCII file format that can be used to combine or process data

generated by receivers made by different manufacturers. RINEX was originally developed at the Astronomical

Institute of the University of Berne. Version 2, containing the latest major changes, appeared in 1990;

subsequently, minor refinements were added in 1993. To date, there are three different RINEX file types. Each of

the file types consists of a header section and a data section, and includes the following information4:

•observation files (carrier-phase measurements; pseudorange / code measurements; times

of observations)

•broadcast navigation message files (orbit data for the satellites tracked; satellite clock

parameters; satellite health condition; expected accuracy of pseudorange measurements;

parameters of single-frequency ionospheric delay model; correction terms relating GPS

time to UTC)

•meteorological data files (barometric pressure; dry air temperature; relative humidity;

zenith wet tropospheric path delay; time tags)

NOTE: Although RINEX is intended to be a receiver-independent format, there are many optional records and

fields. Please keep this in mind when combining NovAtel and non-NovAtel RINEX data.

4. For further information on RINEX Version 2 file descriptions, you ma y wish to consult relevant artic les

in scientific journal such as:

Gurtner, W.G. Mader (1990): “Receiver Independent Exchange Format Version 2.” CSTG GPS

Bulletin Vol. 3 No. 3, Sept/Oct 1990, National Geodetic Survey, Rockville.