20
Appendix C - TRIUMPH-LS AntCal
Appendix C - TRIUMPH-LS AntCal Data
http://www.ngs.noaa.gov/ANTCAL/Antennas.jsp?manu=Javad
TRIUMPH-LS
shown above with its slant height measurement
point (SHMP). The green triangle is also printed on the op-
posite side of the unit.
The display screen is the antenna’s north reference; that is,
the direction the antenna should be facing when doing pre-
cise surveying. Because the Phase Center Offset values for
both L1 and L2 are less than 1 mm in northing and easting
from the central vertical axis, there is negligible impact due
to improper orientation.
PREFACE
ARPs
The
TRIUMPH-LS
requires the 25 mm x 1/4” x 20 threaded
adapter [10-590293-01] to be used whenever the unit is
attached to a 5/8” x 11 threaded fitting. The Antenna Ref-
erence Point (ARP) is the bottom of the
TRIUMPH-LS
. Accord-
ingly, always be sure to remember to add that 25 mm when
using a 2-meter fixed-height GPS pole.
PCOs and PCVs
Beginning in January 2015, NGS is listing the model anten-
na type for the internal antenna of the
TRIUMPH-LS
as the
JAVTRIUMPH_LSA
. Additionally, the antenna calibration
data for the internal antenna has been updated. This sep-
arate distinction relates to both
Phase Center Offset
and
Phase Center Variation
values for the internal antenna of
the
TRIUMPH-LS
.
The original PCOs and PCVs that the NGS Antenna Calibra-
tion team had initially determined in October 2013 have
been superseded by the highly precise values produced
after recalibration on a Geo++ robot. These so-called
near-
field
calibrations included the use of the 25mm x 1/4” x 20
threaded adapter [10-590293-01] and is reflected by the
suffix
A
attached at the end of the antenna model’s name:
JAVTRIUMPH_LSA
. Finalization was coordinated through the
International GNSS Service (IGS) in December 2014.
If survey work has been performed with the
TRIUMPH-LS
and
processed using the superseded NGS values and which had
critical elevation determinations, users are advised to reex-
amine those projects and to reprocess their data using the
superior antenna model published in January 2015.
Differences in the elevation of surveyed points have been
reported to be as much as 2 to 3 cm as improper Phase Cen-
ter Variations will cause errors most notably in the vertical
component in precise GPS surveys
1
.
1
For further reading on this general subject, please see the excellent National
Research Institute of Astronomy and Geophysics (NRIAG) article:
Influence
of GPS antenna phase center variation on precise positioning
, by
Dr. Ahmed I. EL-Hattab which appeared in NRIAG Volume 2, Issue 2, December
2013, Pages 272-277.
