NMEA PASHR Output Format Added

The latest version of the RT3000 software includes an option to output the NMEA PASHR string.

 

NMEA is the common output format used by GPS receivers almost universally. The standard was expandable but did not originally contain any way of encoding roll and pitch information. The PASHR message has become a “standard”, used by many companies, for encoding full orientation information: roll, pitch and heading.

 

Many survey applications, for example Geo-3d’s KRONOS (www.geo-3d.com), a geo-referenced image acquisition system, make use of the PASHR output to give the user a real-time update. NMEA outputs are not efficient and it is not suitable for 100Hz updates; the 100Hz updates are usually merged post-mission.

 

By outputting NMEA we make the RT3000 more compatible with other people’s systems. Many customers have included NCOM decoders into their software but, for new applications, it is often easier to get going using the standard outputs first.

 

The PASHR format is as follows:

 

$PASHR,hhmmss.sss,hhh.hh,T,rrr.rr,ppp.pp,xxx.xx,a.aaa,b.bbb,c.ccc,d,e*ff<CR><LF>

 

where:

 

hhmmss.sss – UTC time

hhh.hh – Heading in degrees

T – flag to indicate that the Heading is True Heading (i.e. to True North)

rrr.rr – Roll Angle in degrees

ppp.pp – Pitch Angle in degrees

xxx.xx – Heave, this is not implemented in the RT3000 and is always “+00.00”

a.aaa – Roll Angle Accuracy Estimate (Stdev) in degrees

b.bbb – Pitch Angle Accuracy Estimate (Stdev) in degrees

c.ccc – Heading Angle Accuracy Estimate (Stdev) in degrees

d – Aiding Status

e – IMU Status

ff – Checksum, computed as usual for NMEA messages

 

The maximum length of the message is 77 characters, conforming to the NMEA standard.

 

For example:

 

$PASHR,085335.000,224.19,T,-01.26,+00.83,+00.00,0.101,0.113,0.267,1,0*06