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viasis 3003 user manual
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As soon 3 to 4 satellites signals could be found appears the output of position data – the lati-
tude in degree and minutes with 4 minute decimals, the N/S latitude information and the
analogous data for the longitude.
The last number, the HDOP
value is a measure for the horizontal, two dimensional variation
of the measured GPS data. GPS position data with a HDOP value greater than 10 are not pre-
cise and not usable.
With the GPS data output you may check if a sufficient number of satellites re-
spectively the GPS position is found at a viasis mounting place within a
reasonable time. In tunnels or in between high buildings the determination of the
GPS position might be impossible. In such a case switch the GPS position deter-
mination off, see chapter 6.4.3.4, in order to avoid a permanent searching GPS module with
the consequence of a reduced operation time of a viasis with battery supply.
6.4.3.3 GPS raw data (NMEA-183 protocol)
The GPS raw data output delivers position data coded according the nautical standard NMEA
developed for the communication between navigation system of ships. These ASCII block data
send once per second are a bit confusing, but include numerous information, amongst other
things e. g. to the satellites, whose data were used for the calculation of the position:
$GPRMC,073114.000,A,5103.5574,N,00700.9062,E,0.00,0.00,011015,,,A*64
$GPVTG,0.00,T,,M,0.00,N,0.01,K,A*3C
$GPGGA,073114.000,5103.5574,N,00700.9062,E,1,7,1.05,75.5,M,47.6,M,,*63
$GPGSA,A,3,05,25,26,29,31,21,23,,,,,,1.36,1.05,0.86*01
$GPGSV,3,1,12,29,71,062,52,31,54,235,46,26,44,296,48,25,40,118,49*70
$GPGSV,3,2,12,21,37,178,37,39,28,157,,05,16,067,46,16,16,296,44*79
$GPGSV,3,3,12,20,11,116,47,23,09,320,45,02,09,039,44,12,,,39*4D
$GPGLL,5103.5574,N,00700.9062,E,073114.000,A,A*57
In the Internet and the literature a lot of publications describe the contents of the NMEA-183
data blocks, therefore we resign to do it here.
Similar to the formatted data output, see chapter 6.4.3.2, the output of the GPS raw data can
be stopped by simultaneous pressing of the <CTRL> and ‘z’ key.
6.4.3.4 GPS position fix time
A few minutes after the viasis power on the determination of the GPS position is done. The
Position fix time
is the time period after which the determination is regularly repeated.
After insertion
4
in the
GPS
menu, following prompt appears:
Position fix time =
You may enter values between 1 and 255 hours for the position determination interval. The
default value is 24 hours. If you enter 0 the determination of the GPS position is deactivated.
If no valid GPS position can be determined within 60 minutes, the position search will be can-
celled and the GPS module will be switched off until the next viasis power on in order to avoid
a fast unwished battery discharge. This might be the case when operating the viasis within
buildings, tunnels or behind high buildings.
1
HDOP – Horizontal dilution of precision
2
NMEA - National Marine Electronics Assoziation
