Spatial Reference Manual
Page 44 of 158
Version 4.4
04/06/2019
interfere with Spatial's magnetometers.
If you are supplying your own antenna it is important to ensure that the antenna is
able to receive all constellations and not just GPS, otherwise you will not achieve full
performance. It is also important to select an IP67 antenna with an IP67 SMA
connector, otherwise the system will not be environmentally sealed.
It is recommended to use an antenna with the following characteristics:
•
For GPS/GLONASS, a frequency range of 1575 Mhz to 1606 Mhz
•
For GPS/BeiDou, a frequency range of 1559 Mhz to 1593 Mhz
•
For all constellations, a frequency range of 1559 Mhz to 1606 Mhz
•
Minimum gain of 15 dB and maximum gain of 50 dB
•
Antenna LNA noise of < 2 dB
•
Out of band rejection of 35 dB @
±70 MHz
9.6
Odometer
On ground vehicles, the use of an odometer input can greatly improve Spatial's
navigation and orientation solution during GNSS dropouts. With a high resolution
wheel encoder Spatial can be used to navigate indoors with GNSS disabled altogether.
There are several different options for odometer installation which are listed below.
9.6.1
Factory VSS Signal
Most road cars since 1980 contain a VSS (vehicle speed sensor) signal that can be
wired directly into one of Spatial's GPIO pins. The vehicle should be taken to an
automotive electrician to perform the work.
To setup the odometer, the appropriate GPIO pin should be set to odometer input
using Spatial Manager, see section 11.8.7. The odometer pulse length must then be
set either manually or automatically, please see section 10.9 for more information.
For more information on the GPIO signals and their requirements please see section
12.4.3.
9.6.2
OBDII Odometer Interface
For applications where it is undesirable to modify the vehicle or the system needs to
be used with multiple vehicles, the OBDII odometer interface may be a better solution.
OBDII is a vehicle diagnostic port standard and most vehicles from the mid 1990s
onwards contain an OBDII port in the drivers side foot well. Advanced Navigation
produces an OBDII odometer interface that plugs into this OBDII port and feeds Spatial
with odometer data over the Auxiliary RS232 port, please see Illustration 17. These
units are priced at approximately AUD 500. Please contact Advanced Navigation sales
for more information.
