Navman 11 User Manual

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MN002000A © 2004 Navman NZ Ltd. All rights reserved. Proprietary information and specifications subject to change without notice.

4.3.4 Differential GPS (DGPS) control
Jupiter GPS DGPS operation: disable and 

correction timeout. When DGPS disable is 

asserted, the navigation solution is computed 

without the benefit of differential corrections even 

if they are available. The DGPS timeout parameter 

is used to specify the maximum allowable time 

difference between current time and the validity 

time of the DGPS corrections. If the timeout 

is exceeded, DGPS navigation solutions are 

unavailable until the correction time delta becomes 

less than the timeout (see sections 4.6 and 4.7).

4.3.5 Cold start control
A simple control that enables or disables this 

feature and sets the timeout for automatic 

transition to cold start is available (see section 4.4 

for a description of this feature).

4.3.6 Solution validity criteria
This configuration feature allows the user to 

specify a set of conditions that must be met for 

a navigation solution to be reported as valid. 

Constraints that can be imposed on solution 

validity include: use of DGPS corrections, use of 

altitude, minimum number of satellites, maximum 

expected position errors (EHPE and EVPE). (See 

section 4.6 for a description of this feature.)

4.3.7 User-entered altitude
This configuration feature allows the user to 

supply a known value of altitude that can be used 

to improve the overall quality of the navigation 

solution. The most common application of this 

feature is to provide a mean sea level value for 

a boat that is used exclusively on an ocean (see 

section 4.6).

4.3.8 Vehicle platform select
This configuration feature allows the user to 

specify the type of vehicle in which the Jupiter 

receiver has been installed (see section 4.6).

4.3.9 Navigation control
Several navigation control features are provided by 

the Jupiter GPS receivers. These features are: 

• groundtrack smoothing
• position pinning
• validity criteria. 

(See section 4.6 for more details.)

4.3.10 Configuration straps
Configuration straps control the use of available 

configuration data at the time of initialisation. 

These straps act as metacommands that can 

override or complement an existing set of 

configuration data. 
Note: These straps are only read once at 

When asserted, the host serial communication 

interface is configured for NMEA operation (4800-

8-N-l). Configuration data related to the host port 

that may be available from other sources is not 

used. When de-asserted, operation of the host 

port is controlled by any available configuration 

data sources (SRAM, EEPROM, etc.). Details of 

the NMEA guarantee that the receiver is started in 

a known message set are contained in Section 5.0 

of this document.

When asserted, all configuration and initialisation 

data are obtained from ROM defaults. In addition, 

SRAM is cleared to guarantee that the receiver 

is started in a known operational state. The host 

serial communication interface is configured for 

Navman binary operation

(9600-8-N-1). When de-asserted (the normal 

operational state), configuration and initialisation 

data are obtained from all valid sources (SRAM, 

EEPROM RTC, etc.).

Jupiter GPS receivers have four types of start-up 

modes (warm, initialised, cold, and frozen) based 

on the availability and source of initialisation data. 

Each of these modes are briefly described in the 

following paragraphs.

4.4.1 Warm start
This state is present when all key data (PVT, 

ephemeris, and frequency standard parameters) 

is valid and available in SRAM. Two common 

conditions that result in this state are a software 

reset (‘hot’ start) after continuous navigation or 

a return from an ‘idle’ period (power cycle) of a 

few minutes that was preceded by a period of 

continuous navigation. 

4.4.2 Initialised start
This state is similar to warm start except that 

ephemeris data is not available at start-up, 

implying that SRAM was not powered during 

the “idle” state or that the data time validity has 

expired. Common conditions that result in this 

state are user-supplied PVT initialisation or 

continuous RTC operation with an accurate last 

known position available from EEPROM. 

4.4.3 Cold start
This state occurs as a result of unknown position 

and/ or time, either of which causes an unreliable 

satellite visibility list. Almanac information is