6
using SBAS. At low speed (L), we measured distance errors
of 1.22 m (4.00 ft) using RTK and 1.54 m (5.05 ft) using
SBAS. Combining speed and direction of travel, for mov-
ing forward at high speed (H) we measured distance errors
of 1.23 m (4.04 ft) with RTK and 1.81 m (5.94 ft) using
SBAS, and at low speed, we measured distance errors of
1.27 m (4.17 ft) with RTK and 1.6 m (5.25 ft) using SBAS.
Moving in reverse at high speed (H), we measured distance
errors of 1.06 m (3.48 ft) with RTK and 1.51 m (4.95 ft)
using SBAS, and distance errors of 1.16 m (3.81 ft) with
RTK and 1.47 m (4.82 ft) using SBAS at low speed (L).
For the e-truck, GNSS status had virtually no effect on the
measured distance error in positional accuracy. As shown in
Table 3, independent of speed and direction of travel, we
estimated a Euclidian error of 1.45 m (4.78 ft) using RTK
and 1.43 m (4.69 ft) using SBAS.
The speed of the vehicles affected the distance errors
independent of the date of testing and other variables. For
the UGV, as the speed increased, the estimated errors gen-
erally increased independent of and in combination with
other variables (see Table 2). It was a similar case for the
e-truck, independent of and in combination with other
variables. Except for the return tests with RTK combina-
tion (see Table 3), NIOSH researchers measured distance
errors that ranged from 0.66–1.92 m (2.17–6.30 ft) for the
5-mph tests, 0.81–2.03 m (2.66–6.66 ft) for the 10-mph
tests, and 0.97–2.14 m (3.18–7.02 ft) for the 15-mph tests.
For either vehicle, the direction of travel had zero effect
on the results. Independent of testing dates, GNSS status,
and speed, the results showed a higher estimate in distance
errors in positional accuracies for the tests going forward
than the tests moving in reverse travel for the UGV or
moving in return travel for the e-truck (see Table 1). It also
seemed to be the case for the UGV test results in com-
bination with other variables (see Table 2). However, this
seems to be misleading. The results are different upon closer
Table 1. Aggregate results for both vehicle accounts for GNSS status, direction of travel, and speed
GNSS Status F or R Speed Estimate (m) Lower 95 CI (m) Upper 95 CI (m)
RTK 1.34 0.99 1.69
SBAS 1.50 1.15 1.85
F 1.09 0.74 1.44
R 1.75 1.4 2.1
15 mph 1.55 1.04 2.05
10 mph 1.43 0.92 1.93
5 mph 1.34 0.83 1.84
H (2.59 mph) 1.41 0.97 1.85
L (1.27 mph) 1.38 0.94 1.82
Table 2. 95% confidence interval (CI) test results for UGV
GNSS Status Direction Speed Estimate (m) Lower 95 CI (m) Upper 95 CI (m)
RTK 1.18 0.65 1.72
SBAS 1.60 1.06 2.14
RTK F 1.25 0.71 1.78
RTK R 1.11 0.58 1.65
SBAS F 1.71 1.17 2.25
SBAS R 1.49 0.95 2.03
RTK 2.59 mph (H) 1.15 0.61 1.68
RTK 1.27 mph (L) 1.22 0.68 1.75
SBAS 2.59 mph (H) 1.66 1.13 2.20
SBAS 1.27 mph (L) 1.54 1.00 2.07
RTK F 2.59 mph (H) 1.23 0.69 1.77
RTK F 1.27 mph (L) 1.27 0.73 1.80
RTK R 2.59 mph (H) 1.06 0.53 1.60
RTK R 1.27 mph (L) 1.16 0.63 1.70
SBAS F 2.59 mph (H) 1.81 1.28 2.35
SBAS F 1.27 mph (L) 1.60 1.06 2.14
SBAS R 2.59 mph (H) 1.51 0.98 2.05
SBAS R 1.27 mph (L) 1.47 0.93 2.01
using SBAS. At low speed (L), we measured distance errors
of 1.22 m (4.00 ft) using RTK and 1.54 m (5.05 ft) using
SBAS. Combining speed and direction of travel, for mov-
ing forward at high speed (H) we measured distance errors
of 1.23 m (4.04 ft) with RTK and 1.81 m (5.94 ft) using
SBAS, and at low speed, we measured distance errors of
1.27 m (4.17 ft) with RTK and 1.6 m (5.25 ft) using SBAS.
Moving in reverse at high speed (H), we measured distance
errors of 1.06 m (3.48 ft) with RTK and 1.51 m (4.95 ft)
using SBAS, and distance errors of 1.16 m (3.81 ft) with
RTK and 1.47 m (4.82 ft) using SBAS at low speed (L).
For the e-truck, GNSS status had virtually no effect on the
measured distance error in positional accuracy. As shown in
Table 3, independent of speed and direction of travel, we
estimated a Euclidian error of 1.45 m (4.78 ft) using RTK
and 1.43 m (4.69 ft) using SBAS.
The speed of the vehicles affected the distance errors
independent of the date of testing and other variables. For
the UGV, as the speed increased, the estimated errors gen-
erally increased independent of and in combination with
other variables (see Table 2). It was a similar case for the
e-truck, independent of and in combination with other
variables. Except for the return tests with RTK combina-
tion (see Table 3), NIOSH researchers measured distance
errors that ranged from 0.66–1.92 m (2.17–6.30 ft) for the
5-mph tests, 0.81–2.03 m (2.66–6.66 ft) for the 10-mph
tests, and 0.97–2.14 m (3.18–7.02 ft) for the 15-mph tests.
For either vehicle, the direction of travel had zero effect
on the results. Independent of testing dates, GNSS status,
and speed, the results showed a higher estimate in distance
errors in positional accuracies for the tests going forward
than the tests moving in reverse travel for the UGV or
moving in return travel for the e-truck (see Table 1). It also
seemed to be the case for the UGV test results in com-
bination with other variables (see Table 2). However, this
seems to be misleading. The results are different upon closer
Table 1. Aggregate results for both vehicle accounts for GNSS status, direction of travel, and speed
GNSS Status F or R Speed Estimate (m) Lower 95 CI (m) Upper 95 CI (m)
RTK 1.34 0.99 1.69
SBAS 1.50 1.15 1.85
F 1.09 0.74 1.44
R 1.75 1.4 2.1
15 mph 1.55 1.04 2.05
10 mph 1.43 0.92 1.93
5 mph 1.34 0.83 1.84
H (2.59 mph) 1.41 0.97 1.85
L (1.27 mph) 1.38 0.94 1.82
Table 2. 95% confidence interval (CI) test results for UGV
GNSS Status Direction Speed Estimate (m) Lower 95 CI (m) Upper 95 CI (m)
RTK 1.18 0.65 1.72
SBAS 1.60 1.06 2.14
RTK F 1.25 0.71 1.78
RTK R 1.11 0.58 1.65
SBAS F 1.71 1.17 2.25
SBAS R 1.49 0.95 2.03
RTK 2.59 mph (H) 1.15 0.61 1.68
RTK 1.27 mph (L) 1.22 0.68 1.75
SBAS 2.59 mph (H) 1.66 1.13 2.20
SBAS 1.27 mph (L) 1.54 1.00 2.07
RTK F 2.59 mph (H) 1.23 0.69 1.77
RTK F 1.27 mph (L) 1.27 0.73 1.80
RTK R 2.59 mph (H) 1.06 0.53 1.60
RTK R 1.27 mph (L) 1.16 0.63 1.70
SBAS F 2.59 mph (H) 1.81 1.28 2.35
SBAS F 1.27 mph (L) 1.60 1.06 2.14
SBAS R 2.59 mph (H) 1.51 0.98 2.05
SBAS R 1.27 mph (L) 1.47 0.93 2.01