As mentioned above, the length of the between successive epochs of data) is
uniform interval governed by the
GPS receiver hardware and accurate interpolation of the aircraft trajectory.
may be the limiting factor for the the exposure station position from The interpolation precision is well
correlated to the limit of positional expected from kinematic GPS (Lapine, intervals degrade the interpolation.
resolution which can be
used GPS data collected at a 1-second rate to 2-second and 5-second rates by removing
The thinned data sets
and then thinned the appropriate interpolated for used for this test
came from two data sets collected aboard the jet and one data set from the Texas Highway
NOAA Citation II Department King
Comparison of the interpolated positions with
position difference was greater than 20 centimeters was recorded
The Citation and King Air results are still commensurate kinematic positioning expectations when thinned to 2
The sample standard deviations for the
to 5 seconds in position. the standard
for the King Air suggest a serious It is interesting to note that the deviations associated with the NOAA
data thinned degradation magnitude of Citation are
were tested and
King Air. The population equality test based on the F
populations are most likely caused by the aircraft trajectories over a time
the inability to model span greater than 2
or may be receivers
caused by a larger used for the tests
signal-to-noise ratio in the
should be avoided if the positioning is required.
full accuracy of kinematic GPS However, the good comparison between
the data thinned to validate the ability at 1 hertz.
2 seconds and observed positions does of the interpolation process when sampling
would be to activate the camera shutter pulse generated by the GPS receiver. may be able to entirely eliminate the
with the 1-second timing In this procedure one time difference between
GPS fix information and exposure.
constant response aircraft
time offset between the timing signal and the camera
to the signal. indicated that
A short test conducted aboard the NOAA the time delay would be on the order
of 0.1 test.
second for the particular Wild RC-10 camera used in the The camera service manual states that the maximum time
delay between rotating shutter blade opening and capping shutter
shutter speed, position of the time the pulse was initiated,
rotating shutter blades and the vacuum status.
One major problem with this procedure to accurately control overlap.