SETAPPROXTIME
Sets an approximate GPS reference time
|
Platform: |
OEM719, OEM729, OEM7500, OEM7600, OEM7700, OEM7720, PwrPak7, CPT7, CPT7700, SMART7, SMART2 |
This command sets an approximate time in the receiver. The receiver uses this time as system time until a coarse time can be acquired. This can be used in conjunction with an approximate position (see the SETAPPROXPOS command) to improve Time To First Fix (TTFF). For more information TTFF and Satellite Acquisition, refer to An Introduction to GNSS available on our website at novatel.com/an-introduction-to-gnss.
The time entered should be within 10 minutes of the actual GPS reference time. If the week number entered does not match the broadcast week number, the receiver resets once it is tracking.
Message ID: 102
Abbreviated ASCII Syntax:
SETAPPROXTIME week sec
Input Example:
SETAPPROXTIME 1930 501232
|
|
Upon power up, the receiver does not know its position or time and therefore cannot use almanac information to aid satellite acquisition. You can set an approximate GPS reference time using the SETAPPROXPOS command. Approximate time and position may be used in conjunction with a current almanac to aid satellite acquisition. See the table below for a summary of the OEM7 family commands used to inject an approximated time or position into the receiver:
Base station aiding can help in these environments. A set of ephemerides can be injected into a rover station by broadcasting the RTCAEPHEM message from a base station. This is also useful in environments where there is frequent loss of lock. GPS ephemeris is three frames long within a sequence of five frames. Each frame requires 6 s of continuous lock to collect the ephemeris data. This gives a minimum of 18 s and a maximum of 36 s continuous lock time or when no recent ephemerides (new or stored) are available. |
|
Field |
Field Type |
ASCII Value |
Binary Value |
Description |
Format |
Binary Bytes |
Binary Offset |
|
1 |
Command header |
- |
- |
SETAPPROXTIME header This field contains the command name for abbreviated ASCII or the message header for ASCII (see page 1) or Binary (see page 1). |
- |
H |
0 |
|
2 |
week |
0-9999 |
GPS reference week number |
Ulong |
4 |
H |
|
|
3 |
sec |
0-604800 |
Number of seconds into GPS reference week |
Double |
8 |
H+4 |
|