guideline and standards for skytem measurements, processing and ...

January 2011
steps to the next time interval. The second step is a polynomial fit to the remaining data from pass 1, and
data are sampled to Beat Time.
Parameters Value Comment
Device All Use one or all devices
Tilt Correction Threshold [s] 5 If no tilt data is found within this time span no tilt correction is
made.
First Filter Poly Order 8 The order of the polynomial used in the first filtering of the altitude
data
First Filter Number of Passes 8 Numbers of time (passes) the first polynomial fit is applied.
First Filter Shift Length [s] 6 Time interval that are used for evaluation (center par of Filter
Length).
First Filter Length [s] 30 Time interval for each polynomial fit.
First Filter Lower Threshold [m] 1 Data that are below the polynomial minus the threshold value
are discarded before the next pass. (reflections from tree tops
etc.)
First Filter Upper Threshold [m] 30 Data that are about the polynomial plus the threshold value are
discarded before the next pass. (incorrect readings from altimeter)
Second Filter Poly Order 8 Order of the polynomial used to fit the remaining data from the
first filtering.
Second Filter Length [s] 30 Time interval for each polynomial fit.
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In the table below recommended settings for the Voltage data Processor are listed. The settings most likely
need to be adjusted to the current survey to result in an optimum processesing of the data.
The time values given for the Trapez. Filters in the table match a flight speed of approximate 45 km/h
(12.5m/s), and the values need to be adjusted if the flight speed differs significantly from this speed. The
selected average widths (Trapez Width 1 2 3) are optimized based on the signal-to-noise ration for the survey
area.
Note: For the Cap filters and the Ave filters, the assumed noise level, the min. and max. slope, and the
back step value have much influence on the number of data that are automatically disabled.
Parameter
SLM/
LM
HM
Comment
Noise Channel OFF OFF Define if the Channel is a Noise channel or not.
Use 2nd order slope filters ON ON ON: all Slope Filters will be based on the change in
slope of the db/dt sounding curve ("2nd order derivate").
When set OFF all Slope Filters will be based on slope of
the db/dt sounding curve.
Sounding Bin Spacing [s] 2 3 Not in use, but is included for compatibility reasons.
Current Time Distance 0.5 0.5 Not in use, but is included for compatibility reasons for
old data.
Cap Sign Filter ON ON Sign filters cull data if a sign change is found.
Cap Sign from time [s] 1.5e-5 1e-4 Data points before this time are not evaluated by the
sign filter.
Cap Sign noise level (ms) [v/m2] 5e-7 2e-7 Defines the assumed noise level at 1 ms. Data points
below noise function formed by the noise level and the
noise slope are not evaluated.
Cap Sign noise slope -0.5 -0.5 Defines the slope of the noise function
Cap Sign back step 30 30 Number of additional data points backwards to be removed
from the data curve
Cap Slope Filter ON ON Sets filter on/off. Slope filters cull data if the slope or the
chance in slope (2nd order slope ON) of the dB/dt
sounding curve is not within specified min/max slopes
interval
2