H220 Integrator Guide Appendix A- FAQ Page A5
GNSS Reception and Performance
How do I know what the H220 is doing?
The H220 supports standard NMEA data messages. The $GPGSV and Bin99 data messages
contain satellite tracking and SNR information. If available, the computed position is contained in
the $GPGGA message. Additionally, the H220 has surface-mounted status LEDs that indicate
receiver status.
Do I have to be careful when using the H220 to ensure it tracks properly?
For best performance, the H220 antenna must have a clear view of the sky for satellite tracking.
The H220 can tolerate a certain amount of signal blockage because redundant satellites are
often available. Only four satellites are required for a position; however, the more satellites that
are used, the greater the positioning accuracy.
SBAS Reception and Performance
How do I know if the H220 has acquired an SBAS signal?
The H220 outputs the $RD1 message that contains the SBAS Bit Error Rate (BER) for each
SBAS channel. The BER value describes the rate of errors received from SBAS. Ideally, this
should be zero. However, the H220 performs well up to 150 BER. The SLXMon and
PocketMax4 utilities provide this information without needing to use NMEA commands.
How do I know if the H220 is offering a differentially-corrected or RTK-corrected
position?
The H220 outputs the $GPGGA message as the main positioning data message. This message
contains a quality fix value that describes the GPS status. If this value is 2, the position is
differentially corrected; if this value is 5, the position is RTK-corrected. The SLXMon and
PocketMax4 utilities provide this information without needing to use NMEA commands.
How do I select an SBAS satellite?
By default, the H220 will automatically attempt to track the appropriate SBAS satellites. If
multiple satellites are available, the one with the lowest BER value is selected to be used to
decode the corrections.
You can manually select which SBAS satellites to track (not recommended). Refer to the
Hemisphere GNSS Technical Reference Guide.
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