WAAS °95% ERROR ° DRIFT/min ° AVG.ERROR* ° END TIME ° RUN TIME ° AVG.ALT.ERROR*#
Vista 2.15 on 5.8m 3m 3.4m@282° 11:21am 30 min. -2m
Vista 2.15 off 7.6m 3m 5.1m@309° 11:59am 30 min. -2m
Magellan M-330 n/a 8.4m 0m** 7.0m@001° 12:30pm 30 min. -1m
Magellan 330 WAAS on 2.5m 1m** 2.0m@273° 10:36am 30 min. 0m
Vista 2.15 on 2.1m 3m 0.9m@306° 10:33pm 30 min. -6m
Vista 2.15 off 1.8m 2m 0.7m@352° 11:08pm 30 min. -8m
G-76 Map 2.04 on 1.8m 2m 0.8m@292° 7:05pm 30 min 0m
G-76 Map 2.04 off 1.9m 2m 0.7m@292° 6:24pm 30 min +1m
Magellan M-330 n/a 2.0m 1m** 1.0m@267° 10:33pm 1 hr. -2m
*Error after averaging in 2-D
#Based on a newly surveyed altitude of 314m
** Due to automatic averaging
GPS accuracy is generally better at night when the ionospheric errors are less.
WAAS ionospheric corrections are therefore less apparent at night.
The reference-point accuracy is confirmed with the average night error of 0.8m.
This (and other) tests indicates non-corrected GPS units have a northward error bias.
The WAAS (WGS-84 datum) receivers have a nighttime north-westward bias
1m as compared to the reference point which was established with DGPS (NAD-83 datum).
In the Atlanta area, WGS-84 coordinates are 0.86m@329° from NAD-83 coordinates.
Those that would like to measure this offset at their loaction can run HTDP.EXE or
the interactive version (HERE).
Survey: USInfrastructure, Inc. later confirmed that the original DGPS averaging in the NAD-83 datum was accurate to within 0.05" of Lat/Long.
Vista WAAS ON, 95% Errors=5.8m
Vista WAAS OFF, 95% Errors=7.6m
Magellan M-330, 95% Errors=8.40m
Magellan M-330 with WAAS, 95%=2.5m
Vista WAAS ON, 95% Errors=2.1m
Vista WAAS OFF, 95% Errors =1.8m
G-76 Map WAAS On, 95%=1.8m
G-76 Map WAAS Off, 95%=1.9m
Magellan M-330, 95% Errors=2.0m