SSRC3

Command Line Interface Reference Guide
____________________________________________________________________________________


Applicable to version 3.4.0 of the GNSS Firmware

SSRC3 Command Line Interface Reference Guide

October 27, 2014 

Applicable to version 3.4.0 of the GNSS Firmware

© Copyright 2000-2014 Septentrio nv/sa. All rights reserved.

Septentrio Satellite Navigation
Greenhill Campus, Interleuvenlaan 15G
B-3001 Leuven, Belgium

List of Contents

List of Acronyms

1 Introduction

1.1 Scope

This document describes the ASCII command-line interface supported by your receiver. The Command and Log Reference Card provides a synopsis of all commands.

1.2 Typographical Conventions

2 Outline

The receiver outputs a prompt when it is ready to accept a user command. The prompt is of the form:
  CD>
where CD is the connection descriptor of the current connection (e.g. COMx or USBx). For instance, if a user is connected to COM1, the prompt will be:
  COM1>
Most commands fall into one of the following categories:
  set-commands to change one or more configuration parameters;
  get-commands to get the current value of one or more configuration parameters;
  exe-commands to initiate some action;
  lst-commands to retrieve the contents of internal files or list the commands.

Each set-command has its get-counterpart, but the opposite is not true. For instance, the setNMEAOutput command has a corresponding getNMEAOutput, but getReceiverCapabilities has no set-counterpart. Each exe-command also has its get-counterpart which can be used to retrieve the parameters of the last invocation of the command.

The prompt indicates the termination of the processing of a given command. When sending multiple commands to the receiver, it is necessary to wait for the prompt between each command.

2.1 Command Line Syntax

Each ASCII command line consists of a command name optionally followed by a list of arguments and terminated by <CR>, <LF> or <CR><LF> character(s) usually corresponding to pressing the "Enter" key on the keyboard.

To minimize typing effort when sending commands by hand, the command name can be replaced by its 3- or 4-character mnemonic. For instance, grc can be used instead of getReceiverCapabilities.

The receiver is case insensitive when interpreting a command line.

The maximum length of any ASCII command line is 2000 characters.

For commands requiring arguments, the comma "," must be used to separate the arguments from each other and from the command’s name. Any number of spaces can be inserted before and after the comma.

Each argument of a set-command corresponds to a single configuration parameter in the receiver. Usually, each of these configuration parameters can be set independently of the others, so most of the set-command’s arguments are optional. Optional arguments can be omitted but if omitted arguments are followed by non-omitted ones, a corresponding number of commas must be entered. Omitted arguments always keep their current value.

2.2 Command Replies

The reply to ASCII commands always starts with "$R" and ends with <CR><LF> followed by the prompt corresponding to the connection descriptor you are connected to.

The following types of replies are defined for ASCII commands:

• For comment lines (user input beginning with "#") or empty commands (just pressing "Enter"), the receiver replies with the prompt.
  

  COM1> # This is a comment! <CR>
  COM1>

• For invalid commands, the reply is an error message, always beginning with the keyword "$R?" followed by an error message. The different error messages are listed in Appendix A.
• For all valid set-, get- and exe-commands, the first line of the reply is an exact copy of the command as entered by the user, preceded with "$R:". One or more additional lines are printed depending on the command. These lines report the configuration of the receiver after execution of the command.
  COM1>setNMEAOutput, stream1, com1, GGA, sec1 <CR>
  $R: setNMEAOutput, stream1, com1, GGA, sec1
  NMEAOutput, stream1, com1, GGA, sec1
  COM1>
  

  For commands which reset or halt the receiver (e.g. exeResetReceiver), the reply is terminated by "STOP>" instead of the standard prompt, to indicate that no further command can be entered.
  

• For all valid lst-commands, the first line of the reply is an exact copy of the command as entered by the user, preceded with "$R;". The second line is a pseudo-prompt "$-$$-$$-$$-$>" and the remaining of the reply is a succession of formatted blocks, each of them starting with "$$-$$-$ BLOCK".

ASCII replies to set-, get- and exe-commands, including the terminating prompt, are atomic: they cannot be broken by other messages from the receivers. For the lst-commands, the replies may consist of several atomic formatted blocks which can be interleaved with other output data. If more than one formatted block is output for a lst-command, each of the intermediate blocks is terminated with a pseudo-prompt "$-$$-$$-$$-$>". The normal prompt will only be used to terminate the last formatted block of the reply so that one single prompt is always associated with one command.

2.3 Command Syntax Tables

All ASCII commands are listed in Section 3, "Command List" Each command is introduced by a compact formal description of it called a "syntax table". Syntax tables contain a complete list of arguments with their possible values and default settings when applicable.

The conventions used in syntax tables are explained below by taking a fictitious setCommandName command as example. The syntax table for that command is:

scn gcn	setCommandName  getCommandName	Cd Cd	Distance	Time	Message (120)	Mode	PRN
		Com1 Com2 all	-20.00 …0.00 …20.00 m	1 …50 sec	Unknown	on off	none G01 ... G32 S120 ... S138 SBAS GPS all _

RxControl: Navigation > Receiver Operation > Example
Web Interface: Configuration > Navigation > Receiver Operation > Example

The associated set- and get-commands are always described in pairs, and the same holds for the associated exe- and get-commands. The command name and its equivalent 3- or 4-character mnemonic are printed in the first two columns. The list of arguments for the set- and getcommands is listed in the first and second row respectively. In our example, setCommandName can accept up to 6 arguments and getCommandName only accepts one argument. Mandatory arguments are printed in bold face. Besides the mandatory arguments, at least one of the optional arguments must be provided in the command line.

The list of possible values for each argument is printed under each of them. Default values for optional arguments are underlined.

The fictitious command above contains all the possible argument types:

• Cd serves as an index for all following arguments. This can be noticed by the possibility to use this argument in the get-command. This argument is mandatory in the set-command. The accepted values are COM1, COM2 and all, corresponding to the first or second serial ports, or to both of them respectively. The "+" sign before the first two values indicates that they can be combined to address both serial ports in the same command.
  

  Examples: COM1, COM1+COM2, all (which is actually an alias for COM1+COM2).
  

• Distance is a number between -20 and 20 with a default value of 0, and up to 2 decimal digits. An error is returned if more digits are provided. The "m" indicates that the value is expressed in meters. Note that this "m" should not be typed when entering the command.
  

  Examples: 20, 10.3, -2.34
  

• Time is a number between 1 and 50, with no decimal digit (i.e. this is an integer value). This value is expressed in seconds.
  

  Examples: 1, 10
  

• Message is a string with a maximum length of 120 characters. The default value of that argument is "Unknown". When spaces must to be used, the string has to be put between quotes and these enclosing quotes are not considered part of the string. The list of allowed characters in strings is:
  

  ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789 !#%@()*+-./:;<=>?[\]^_‘{|}~
  

  Example: "Hello World!"
  

• Mode is a range of individual values that cannot be combined (they are not preceded by a "+" sign). Either off or on can be selected for that argument and the default value is on.
  

  Example: on
  

• PRN is a range of values that can be combined together with the "+" sign. The default value GPS is an alias for G01+G02+ ... +G32, SBAS is an alias for S120+ ... +S138 and all an alias for GPS+SBAS. A "+" sign can be set before the argument to indicate to add the specified value(s) to the current list. If the value "none" is supported (which is the case in this example), a "-" sign can be set before the argument to remove the specified value(s) from the current list. It is possible to add or remove multiple values at once by "adding" or "subtracting" them with the "+" or "-" operator. However, "+" and "-" can never be combined in a single argument.
  

  Examples: G01+G02, +G03, GPS+S120, +G04+G05, -S122-S123, -GPS
  

The lines printed in blue under the syntax table show under which menu the command can be found using RxControl or the Web Interface (the latter is only relevant for receivers supporting a web interface).

3 Command List

3.1 Receiver Administration Commands

lai	lstAntennaInfo	Antenna
		Overview Main [antenna name]

Use this command with the argument Antenna set to Overview to get a list of all antenna names for which the receiver knows the phase center variation parameters (see Firmware User Manual for a discussion on the phase center variation).

Use this command with the argument Antenna set to one of the antenna names returned by lstAntennaInfo, Overview to retrieve the complete phase center variation parameters for that particular antenna. Do not forget to enclose the name between double quotes if it contains whitespaces.

Using the values Main will return the phase center variation parameters corresponding to the main antenna type as specified in the command setAntennaOffset.

Examples

help	lstCommandHelp	Action (255)
		Overview

Use this command to retrieve a short description of the ASCII command-line interface.

When invoking this command with the Overview argument, the receiver returns the list of all supported set-, get- and exe-commands. The lstCommandHelp command can also be called with any supported set-, get- or exe-command (the full name or the mnemonic) as argument.

The reply to this command is free-formatted and subject to change in future versions of the receiver’s software. This command is designed to be used by human users. When building software applications, it is recommended to use the formal lstMIBDescription.

Examples

lcf	lstConfigFile	File
		Current Boot RxDefault User1 User2

Use this command to list the contents of a configuration file. A configuration file contains the list of user commands needed to bring the receiver from factory default to a certain non-default configuration.

The following configuration files are available:

File	Description
Current	The current configuration.
Boot	The configuration that is loaded at boot time, after a power cycle or after a hard reset (see also the exeResetReceiver command).
RxDefault	The default configuration.
User1	A user-defined configuration.
User2	A user-defined configuration.

See also the related exeCopyConfigFile command to learn how to manage configuration files.

Example

eccf gccf	exeCopyConfigFile  getCopyConfigFile	Source	Target
		Current Boot User1 User2 RxDefault	Current Boot User1 User2

RxControl: File > Copy Configuration
Web Interface: Receiver > Administration > Copy Configuration

Use this command to manage the configuration files. See the lstConfigFile command for a description of the different configuration files.

With this command, the user can copy configurations files into other configuration files. For instance, copying the Current file into the Boot file makes that the receiver will always boot in the current configuration.

Examples

To save the current configuration in the Boot file, use:

To load the configuration stored in User1, use:

efup gfup	exeFTPUpgrade  getFTPUpgrade	Server (32)	Path (64)	Login (12)	Password (24)
				anonymous

RxControl: File > Upgrade Receiver using FTP
Web Interface: Receiver > Administration > Upgrade Receiver using FTP

Use this command to upgrade the receiver by fetching the upgrade file from an FTP server. The arguments specify the FTP server, the path to the upgrade file (.SUF format), and the login and password to use.

This procedure always resets the receiver, even if the upgrade file does not exist.

Before resetting, the receiver broadcasts a "$TE ResetReceiver" message to all active communication ports, to inform all users of the imminent reset.

After a reset, the user may have to adapt the communication settings of his/her terminal program as they may be reset to their default values.

Example

lif	lstInternalFile	File
		Permissions Identification Debug Error SisError DiffCorrError SetupError LBAS1Access LBAS1Subscr IPParameters

Use this command to retrieve the contents of one of the receiver internal files:

File	Description
Permissions	List of permitted options in your receiver.
Identification	Information about the different components being part of the receiver (e.g. serial number, firmware version, etc.).
Debug	Program flow information that can help support engineers to debug certain issues.
Error	Last internal error reports.
SisError	Last detected signal-in-space anomalies.
DiffCorrError	Last detected anomalies in the incoming differential correction streams.
SetupError	Last detected anomalies in the receiver setup.
LBAS1Access	LBAS1 (L-Band Augmentation Service 1) Access information.
LBAS1Subscr	LBAS1 (L-Band Augmentation Service 1) Subscription status.
IPParameters	Hostname, MAC and IP addresses, DNS addresses, netmask and gateway (gateway shown only in static IP mode, see command setIPSettings).

Example

lmd	lstMIBDescription	File (255)
		Overview SBFTable

Use this command to retrieve the ASN.1-compliant syntax of the user command interface. The name of the command refers to the MIB (Management Information Base), which holds the whole receiver configuration. There is a one-to-one relationship between the formal MIB description and the ASCII command-line interface for all exe-, get- and set-commands.

When the value Overview is used, the general syntax of the interface is returned. With the value SBFTable, the receiver will output the list of supported SBF blocks and whether they can be output at a user-selectable rate or not. The lstMIBDescription command can also be called with every supported set-, get- or exe-command (the full name or the mnemonic) as argument.

No formal description of the lst-commands can be retrieved with lstMIBDescription.

Examples

epwm gpwm	exePowerMode  getPowerMode	Mode
		ScheduledSleep StandBy

RxControl: File > Power Mode > Shut Down
Web Interface: Receiver > Administration > Power Mode > Shut Down

Use this command to set the receiver in sleep or stand-by mode, in which it consumes only a fraction of its normal operational power.

When in ScheduledSleep or StandBy mode, the receiver can be awoken by sending the appropriate signal to one of its input pins, or by sending a character to the first COM port (see the Hardware Manual for details).

When in ScheduledSleep mode, the receiver can also automatically wake up at a given time or at regular intervals. This functionality is controlled by the setWakeUpInterval command.

Upon waking up, the receiver applies the configuration that is stored in the boot configuration file (see the lstConfigFile command).

Before entering sleep or stand-by mode, the receiver broadcasts a "$TE PowerMode" message to all active communication ports, to inform all users of the imminent halt.

Example

grc	getReceiverCapabilities

RxControl: Help > Receiver Interface > Permitted Capabilities
Web Interface: Configuration > Help > Receiver Interface > Permitted Capabilities

Use this command to retrieve the so-called "capabilities" of your receiver. The first returned value is the list of supported antenna(s), followed by the list of supported signals, the list of available communication ports and the list of enabled features.

The three values at the end of the reply line correspond to the default measurement interval, the default PVT interval and the default integrated INS/GNSS interval respectively. This is the interval at which the corresponding SBF blocks are output when the OnChange rate is selected with the setSBFOutput command. These values are expressed in milliseconds.

Each of the above-mentioned lists contain one or more of the elements in the tables below.

Antennas	Description
Main	The receiver’s main antenna.

Signals	Description
GPSL1CA	GPS L1 C/A signal.
GPSL1PY	GPS L1 P(Y) signal.
GPSL2PY	GPS L2 P(Y) signal.
GPSL2C	GPS L2 C signal.
GPSL5	GPS L5 signal.
GLOL1CA	GLONASS L1 C/A signal.
GLOL2P	GLONASS L2 P signal.
GLOL2CA	GLONASS L2 C/A signal.
GLOL3	GLONASS L3 signal.
GALL1BC	Galileo L1 BC signal.
GALE5a	Galileo E5a signal.
GALE5b	Galileo E5b signal.
GALE5	Galileo E5 AltBOC signal.
GEOL1	SBAS L1 C/A signal.
GEOL5	SBAS L5 signal.
CMPL1	COMPASS/BEIDOU B1 signal.
CMPE5b	COMPASS/BEIDOU B2 signal.
QZSL1CA	QZSS L1 C/A signal.
QZSL2C	QZSS L2 C signal.
QZSL5	QZSS L5 signal.
LBAND	MSS L-Band signal.

ComPorts	Description
COM1	Serial port 1.
COM2	Serial port 2.
COM3	Serial port 3.
COM4	Serial port 4.
USB1	Virtual serial port 1.
USB2	Virtual serial port 2.
IP10	TCP/IP port 1.
IP11	TCP/IP port 2.
IP12	TCP/IP port 3.
IP13	TCP/IP port 4.
IP14	TCP/IP port 5.
IP15	TCP/IP port 6.
IP16	TCP/IP port 7.
IP17	TCP/IP port 8.
NTR1	NTRIP port 1.
NTR2	NTRIP port 2.
NTR3	NTRIP port 3.
IPS1	IP Server port 1.
IPS2	IP Server port 2.
IPS3	IP Server port 3.
IPR1	IP Receive port 1.
IPR2	IP Receive port 2.
IPR3	IP Receive port 3.

Capabilities	Description
SBAS	Positioning with SBAS corrections.
DGPSRover	Positioning with DGPS corrections.
DGPSBase	Generation of DGPS corrections.
RTKRover	Positioning with RTK corrections.
RTKBase	Generation of RTK corrections.
RTCMv23	Generation/decoding of RTCM v2.3 corrections.
RTCMv3x	Generation/decoding of RTCM v3.x corrections.
CMRv20	Generation/decoding of CMR v2.0 corrections.
xPPSInput	Internal clock synchronisation with xPPS input signal.
xPPSOutput	Generation of xPPS output signal.
TimedEvent	Accurate time mark of event signals.
InternalLogging	Internal logging.
APME	A-Posteriori Multipath Estimator.
RAIM	Receiver Autonomous Integrity Monitoring.
PPPGlobal	PPP through Wide Area Augmentation Service for global use.
PPPLand	PPP through Wide Area Augmentation Service for land based use.
LBAS1	L Band Augmentation data Service 1.
LBAS1L	L Band Augmentation data Service 1 Land only.
SIGIL	Usage of SIGIL input allowed.

Example

gri	getReceiverInterface	Item
		RxName SNMPLanguage SNMPVersion all

RxControl: Help > Receiver Interface > Interface Version
Web Interface: Configuration > Help > Receiver Interface > Interface Version

Use this command to retrieve the version of the receiver command-line interface. The reply to this command is a subset of the reply returned by the lstInternalFile, Identification command.

Example

era gra	exeRegisteredApplications  getRegisteredApplications	Cd Cd	Application (12)
		COM1 COM2 COM3 COM4 USB1 USB2 IP10 ... IP17 all	Unknown

RxControl: Communication > Registration
Web Interface: Configuration > Communication > Registration

Use these commands to define/inquire the name of the application that is currently using a given connection descriptor (Cd).

Registering an application name for a connection does not affect the receiver operation, and is done on a voluntary basis. Application registration can be useful to developers of external applications when more than one application is to communicate with the receiver concurrently. Whether or not this command is used, and the way it is used is up to the developers of external applications.

Example

erst grst	exeResetReceiver  getResetReceiver	Level	EraseMemory
		Soft Hard Upgrade	none Config PVTData SatData BaseStations all

RxControl: File > Reset Receiver
Web Interface: Receiver > Administration > Reset Receiver

Use this command to reset the receiver and to erase some previously stored data. The first argument specifies which level of reset you want to execute:

Level	Description
Soft	This is a reset of the receiver’s firmware. After a few seconds, the receiver will restart operating in the same configuration as before the command was issued, unless the "Config" value is specified in the second argument.
Hard	This is similar to a power off/on sequence. After hardware reset, the receiver will use the configuration saved in the boot configuration file.
Upgrade	Set the receiver into upgrade mode. After a few seconds, the receiver is ready to accept an upgrade file (SUF format) from any of its connections.

The second argument specifies which part of the non-volatile memory should be erased during the reset. The following table contains the possible values for the EraseMemory argument:

EraseMemory	Description
Config	The receiver’s configuration is reset to the factory default. The Current and Boot configuration files are erased (see the exeCopyConfigFile command). Note that the User1 and User2 configuration files are not erased: use the exeCopyConfigFile command instead. Also, the IP settings set by the commands setIPSettings and setIPPortSettings are not reset.
PVTData	The latest computed PVT data stored in non-volatile memory is erased.
SatData	All satellite navigation data (ephemeris, almanac, ionosphere parameters, UTC, ...) stored in non-volatile memory is erased.
BaseStations	All base stations stored in non-volatile memory are erased.

Before resetting, the receiver broadcasts a "$TE ResetReceiver" message to all active communication ports, to inform all users of the imminent reset.

After a reset, the user may have to adapt the communication settings of his/her terminal program as they may be reset to their default values.

Example

3.2 Authentication Commands

lcu	lstCurrentUser

Use this command to check which user is currently logged in on this port, if any. See also the login command.

Example

sdal gdal	setDefaultAccessLevel  getDefaultAccessLevel	Web	Ftp	Ip	Com	Usb
		none Viewer User	none Viewer User	none Viewer User	none Viewer User	none Viewer User

RxControl: File > User Management
Web Interface: Receiver > Administration > User Management

This command defines what an anonymous user is authorized to do when connected to the receiver. An anonymous user is one who has not logged in with the login command.

The anonymous authorization level can be set independently for the Web interface, the FTP access, TCP/IP ports, COM ports and USB ports.

For the Web, Ip, Com and Usb arguments, setting the authorization level to User grants full control of the receiver to the anonymous user connected through that connection. The Viewer level allows the anonymous user to view the receiver configuration without changing it (i.e. to only issue get-commands). none prevents anonymous users from viewing or changing the configuration.

For the Ftp argument, Viewer means that the anonymous user is allowed to download files, but not to delete them. User means that the anonymous user can both download and delete files.

To perform actions not allowed to anonymous users, you first need to authenticate yourself by entering a UserName and Password through the login command.

See also the commands setUserAccessLevel to learn how to define user accounts.

This command does not change the status of existing connections. In particular, for Com and Usb connections, it will only take effect after a reset.

Example

To require logging in on Web and FTP interfaces, use:

login	LogIn	UserName (16)	Password (32)

Use this command to authenticate yourself. When initially connecting to the receiver, a user is considered "anonymous". The level of control granted to anonymous users is defined by the command setDefaultAccessLevel.

To perform actions not allowed to anonymous users, you need to authenticate yourself by entering a UserName and Password through the login command.

The list of user names and passwords and their respective access level can be managed with the setUserAccessLevel command. Login fails if the provided UserName or Password is not in that list.

The logout command returns to unauthenticated (anonymous) access. The lstCurrentUser command can be invoked to find out which user is logged in on the current port.

It is not necessary to log out before logging in as a different user.

Examples

To log in as user "admin" with password "admin", use

Logging in with a wrong username or password gives an error:

If the user does not have sufficient access right, some commands may give an error:

logout	LogOut

Use this command to return to anonymous access. It is the reverse of login.

Example

The following sequence of commands logs in as user "admin" with password "admin", reconfigures SBF output, and logs out again:

sual gual	setUserAccessLevel  getUserAccessLevel	UserID UserID	UserName (16)	Password (32)	UserLevel
		User1 ... User8 all			Viewer User

RxControl: File > User Management
Web Interface: Receiver > Administration > User Management

Use these commands to manage the users and their access rights on the receiver. Up to eight users can be defined (User1 to User8).

Each user is identified with a UserName and Password, and has a certain level of acces (UserLevel). If UserLevel is User, the user has full control of the receiver. If it is Viewer, the user can only issue get-commands.

Note that the receiver encrypts the password so that it cannot be read back with the command getUserAccessLevel.

Examples

To create a user with name logger, password xghNF%d and "Viewer" access permissions:

To remove a user from the list, use the empty string "" as UserName and Password:

3.3 Tracking Configuration Commands

sam gam	setAGCMode  getAGCMode	Band Band	Mode	Gain
		L1 L2L5 all	auto frozen manual	0 …35 …70 dB

RxControl: Navigation > Advanced User Settings > Frontend and Interference Mitigation > Frontend Settings
Web Interface: Configuration > Navigation > Advanced User Settings > Frontend and Interference Mitigation > Frontend Settings

Use these commands to define/inquire the operation mode of the Automatic Gain Control (AGC) in the receiver frontend. The AGC is responsible for amplifying the input RF signal to an appropriate level.

By default (Mode is set to auto), the AGC automatically adjusts its gain in function of the input signal power. In frozen mode, the AGC gain is kept constant at its current value (after a ten-second stabilisation period) and does not follow any subsequent variation of the input signal power. In manual mode, the user can set the gain to a fixed value specified by the Gain argument. The Gain argument is ignored in auto and frozen modes.

The first argument (Band) specifies for which frequency band the settings apply.

Example

sca gca	setChannelAllocation  getChannelAllocation	Channel Channel	Satellite	Search	Doppler	Window
		Ch01 ... Ch40 all	auto G01 ... G32 F01 ... F21 E01 ... E32 S120 ... S140 C01 ... C32 J01 J02 J03	auto manual	-50000 …0 …50000 Hz	1 …16000 …100000 Hz

RxControl: Navigation > Advanced User Settings > Channel Allocation
Web Interface: Configuration > Navigation > Advanced User Settings > Channel Allocation

Use these commands to define/inquire the satellite-to-channel allocation of the receiver.

The action of the setChannelAllocation command is to force the allocation of a particular satellite on the set of channels identified with the Channel argument, thereby overruling the automatic channel allocation performed by the receiver. It is possible to allocate the same satellite to more than one channel. If you assign a satellite to a given channel, any other channel that was automatically allocated to the same satellite will be stopped and will be reallocated.

The values Gxx, Exx, Fxx, Sxxx, Cxx and Jxx for the Satellite argument represent GPS, Galileo, GLONASS, SBAS, Compass/BeiDou and QZSS satellites respectively. For GLONASS, the frequency number (with an offset of 8) should be provided, and not the slot number (hence the "F"). Setting the Satellite argument to auto brings the channel back in auto-allocation mode.

The user can specify the Doppler window in which the receiver has to search for the satellite. This is done by setting the Search argument to manual. In that case, the Doppler and Window arguments can be provided: the receiver will search for the signal within an interval of Window Hz centred on Doppler Hz. The value to be provided in the Doppler argument is the expected Doppler at the GPS L1 carrier frequency (1575.42MHz). This value includes the geometric Doppler and the receiver and satellite frequency biases. Specifying a Doppler window can speed up the search process in some circumstances. A satellite already in tracking that falls outside of the prescribed window will remain in tracking.