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CHAPTER 4
G N S S O P E R A T I O N S
Global Navigation Satellite System (GNSS) data is used to correct global drift in post-processing
using the loop closure tool. These instructions will both show how to integrate your GNSS unit
with Stencil 2 and how to convert GNSS/non-GNSS type data logged separately into a format
Stencil 2 can use with the Loop Closure Tool.
I N T E G R A T I N G G N S S W I T H S T E N C I L
Select a GNSS unit that outputs data in the NMEA 0183 format through a USB port, Wi-Fi, or
TCP/IP. If possible select $GxGGA, $GxGSA, and $GxZDA as they contain elevation data, various
dilution of precision error estimates, and date/time where most of the other message types do
not. The elevation data and error estimates work closely with the Loop Closure post processing
tool for global drift error correction. If the antenna is small enough, it can be mounted to the top
of Stencil 2 using double sided tape, etc. If it is larger, you may need to build a suitable frame for
mounting the larger antenna such as shown.
Kaarta provides a GNSS solution using the Emlid Reach units fully
integrated with Stencil 2 and available for purchase. Contact
info@kaarta.com for a quote if desired. Kaarta has also integrated this with
a higher accuracy GNSS Trimble BX-992 system.
Set up the GPS unit using a cable for USB or Ethernet to Stencil 2 unless
you are using a Wi-Fi interface.
G P S S E T U P
1.
Turn on Stencil 2 and the GNSS unit.
2.
Select the GNSS Monitor Icon on the Stencil 2 Desktop.
3.
Select whether the type of interface being used (USB or TCP/IP)
4.
Select the USB port being used or enter the IP address and port of the GNSS unit
5.
The GNSS Monitor Icon will now display the status of the GPS data as shown below.
Be sure to set the GPS antenna offsets in the configuration.yaml file.