Sutron Corporation RLR-0003-1 Manuel D’Utilisation
Bringing the Benefits of Real-Time Data Collection to the World
17
Averaging Time
Every time the radar measures it will collect samples for a user defined period (
Every time the radar measures it will collect samples for a user defined period (
) in order to produce a stage reading. The setting avg time determines how long to
collect samples for. Averaging time can be changed via SDI-12
In addition to the averaging time, the
of samples collected. The sample form period determines how often each sample is collected.
Two methods are offered for computing a stage from multiple samples: averaging and DQAP.
Two methods are offered for computing a stage from multiple samples: averaging and DQAP.
Averaging
Adding all the (good) samples and dividing the sum by the number of (good) samples will provide
the average distance to water. In addition to the averaged distance to water, radar will also provide
the average signal strength, the standard deviation of the good samples, the total number of samples
and the number of good samples. Finally, the quality of the stage will be set to good if at least half
of the samples were good. In order to log all these details, make sure to enable the measurement
setup field
the average distance to water. In addition to the averaged distance to water, radar will also provide
the average signal strength, the standard deviation of the good samples, the total number of samples
and the number of good samples. Finally, the quality of the stage will be set to good if at least half
of the samples were good. In order to log all these details, make sure to enable the measurement
setup field
. They can also be accessed via command line or SDI-12.
Averaging is enabled by default. If DQAP is disabled, averaging is enabled (
DQAP
DQAP is a method defined by the NOS (National Ocean Service) of computing the stage that is
designed to eliminate erroneous values from the calculation. With DQAP, the distance to water is
calculated using two computations:
For the first computation, the average and standard deviation of all the samples are calculated.
Then, two limits are figured: the average plus/minus three times the computed standard deviation.
Each sample is then compared against the two limits. If the sample is outside the limits, it will not
be used in the final computation.
In the final computation, the average and standard deviation are recomputed from all the samples
remaining from the first calculation. The quality of the stage reading will be set to good if at least
half of the samples were selected for the secondary computation; it will be set to bad otherwise. The
good sample count of the stage reading will be set to the number of samples selected for the
secondary computation.
designed to eliminate erroneous values from the calculation. With DQAP, the distance to water is
calculated using two computations:
For the first computation, the average and standard deviation of all the samples are calculated.
Then, two limits are figured: the average plus/minus three times the computed standard deviation.
Each sample is then compared against the two limits. If the sample is outside the limits, it will not
be used in the final computation.
In the final computation, the average and standard deviation are recomputed from all the samples
remaining from the first calculation. The quality of the stage reading will be set to good if at least
half of the samples were selected for the secondary computation; it will be set to bad otherwise. The
good sample count of the stage reading will be set to the number of samples selected for the
secondary computation.
To enable DQAP, use the
enabled, averaging is disabled.
, each sample of the stage is actually the average of millions or radar pulses
to the water. The sample form period value controls how much raw radar data to include in each sample.
The default value for sample form period is 1.0 second. Do not change this value without consulting with the
factory. The quality of the sample depends on the number of good subsamples collected. If there are not
enough good subsamples, the quality is set to bad.
The details of each sample can be viewed in the
The default value for sample form period is 1.0 second. Do not change this value without consulting with the
factory. The quality of the sample depends on the number of good subsamples collected. If there are not
enough good subsamples, the quality is set to bad.
The details of each sample can be viewed in the
. The details consist of distance to water,
standard deviation, number of good and number of total subsamples, sample validity, signal strength,
minimum and maximum. Each sample may be logged by activating
minimum and maximum. Each sample may be logged by activating
Log entry
Description
Sample Min
The minimum distance to water
Sample Max
The maximum distance to water
Sample Avg
The average distance to water
Sample StdDev
The standard deviation of all the subsamples
Sample Good Subs
The number of valid subsamples included in the average
Sample Total Subs
The total number of subsamples collected (only the good subsamples are included in
computation)
computation)