GRINGO (GPS RINEX Generator) is a program which has been developed at the I
nstitute of Engineering Surveying and Space Geodesy (IESSG) at the Universi
ty of Nottingham, to record the pseudorange and carrier phase data from 12-
channel Garmin handheld GPS receivers, in standard RINEX (REceiver INdepend
ent EXchange) format. It offers owners of these receivers the possibility o
f post-processing to an accuracy of approximately 5 m (with pseudoranges) o
r a few cm (with carrier phase), without having to invest in separate DGPS
receiving equipment or expensive survey-grade receivers. They retain the be
nefits of an inexpensive receiver wit a user-friendly interface and powerfu
l navigation features, but gain the possibility of improved accuracy if nee
ded.
A number of experiments have bee carried out to assess the accuracy of posi
tioning with Garmin raw measurement data.
Experiments over a 3 km baseline with various session lengths have shown th
at float solutions with the Garmin carrier phase can achieve better than 20
cm in 15 minutes, and approximately 5 cm with 30 minutes. Ambiguity fixed
solutions can achieve approximately 1 cm accuracy in 30 minutes. A zero bas
eline test, with two garmin receivers attached to a single static antenna,
has shown that under ideal conditions, even sub-millimeter accuracies are p
ossible in as little ast 10 minutes.
Over a longer baseline (>200 km), the effects of the atmosphere on the meas
ured with geodetic receivers has confirmed that th atmosphere affects the G
armin receivers in the same way as it does the geodetic receivers.
This paper will present the results of these and other experiments.