0.15

0.6

0.10

0.05

0.4

0

0.05

0.2

0.10

Video

Video

0

0.15

0.15

0.6

0.10

0.05

0.4

0

0.05

0.2

0.10

Radar

Radar

0.15

0

200

400

600

800

0

1000

0

200

400

600

800

1000

Time (s)

Time (s)

ference between the data and the polynomial was

generally less than 0.06. The mean and median

difference are both zero, with an RMS difference

of 0.022 m/s and a maximum difference of 0.065

m/s. The amplitudes of the velocity differences

are within the bounds of experimental error, and

their structure is random. We conclude that the

polynomial adequately describes the video data.

was a difference in velocity of 0.05 m/s, or a nor-

malized velocity difference of 0.09. Data repre-

senting the midpoint of the band obtained at 10-s

intervals, the best fourth-order polynomial fit to

these data, and the normalized difference be-

tween the data and the polynomial are presented

in Figure 12. The mean radar velocity was 0.539

m/s, and the normalized difference was general-

record during the period of dispersed ice motion.

ly less than 0.07. The mean and median differ-

Bands of velocity through time from floes produc-

ences are both zero, with an RMS difference of

ing strong backscatter are clearly visible.

0.023 m/s and a maximum difference of 0.067 m/s.

Small underestimates of α and β would cause a

The amplitudes of the velocity differences are

systematically high radar velocity, corresponding

somewhat larger than would be expected from

to most of the difference between the Doppler

experimental error, and their structure appears

and video mean velocities. In addition, strong in-

periodic. However, the oscillations in this record

dividual reflectors that passed through the radar

are not supported by the video data. The oscillat-

footprint at constant speed spent almost 60% of

ing radar velocities occurred when the open wa-

this time on the high-velocity side of the bore-

ter area in the radar footprint increased and the

sight, potentially introducing a velocity bias.

number of targets decreased. When a single floe

However, for consistency and ease of comparison

traverses the footprint there is an apparent

we again assume that the systematic difference

change in velocity from high to low caused by the

between the radar and video velocities is due to

relationship between vertical angle and Doppler

video grid distortion. The video and radar veloc-

frequency. Figure 13 shows part of the breakup

10