Wavetronix SmartSensor HD (101-0415) - User Guide Manual de usuario descargar pdf (Pagina 68)

CHAPTER 7  DATA 67

memory lls up faster and must be downloaded from more oen. See the Storage section of

this chapter for more information on how to gure out how many days’ worth of memory

your sensor has based on its current settings.

Interval

Interval data refers to the data collected about all the vehicles that pass the sensor in a set

amount of time. is interval of time should be carefully chosen because the length of it

aects how long the sensor can store data onboard. A shorter interval means the sensor

records data more oen, which means that the sensor’s onboard memory lls up faster. A

longer interval means you can leave the sensor alone for longer periods of time. Ultimately

the interval size should be selected to meet the requirements of your application. For ex-

ample, in real-time applications, onboard storage capacity may not be a concern at all and

the data may need to be aggregated over short periods of time (20 seconds) to reduce re-

porting latency. To set the interval, click anywhere inside the Interval eld and use the up/

down arrows to change the interval (see Figure 7.2). See the Storage section in this chapter

for more information.

Once you download the interval data, you will have the following information for each lane

or approach:

 Name – Displays the name of each lane or approach. To change the name, go to the

Lane Conguration screen or the Approaches screen.

 Volume – Shows the number of vehicles detected during the interval.

 Occupancy – Gives the percentage of time during the interval that the detection zone

was occupied.

Occupancy is calculated by summing the durations of all vehicles in the interval and di-

viding that quantity by the length of the interval. For example, if the interval length is ve

minutes and 100 vehicles pass the sensor during the interval with a duration of 0.09 seconds

each (sum of the durations is 9 seconds), then the occupancy for that interval would be

calculated by dividing 9 seconds by 300 seconds, which is 3%.

Rather than using the uncalibrated detection duration, or the time that a vehicle is in the ra-

dar beam, in the occupancy calculation, a more accurate occupancy measurement is made

by rst calculating the vehicle length and then converting that to a duration by adding the

simulated loop size and dividing by the speed. Occupancy based on vehicle length is more

accurate than occupancy based on uncalibrated detection duration because the vehicle

length calculation removes the eect of the antenna beam widening as it gets farther from

the sensor. e occupancy calculation is shown in the following equation:

Interval Size

All Vehicles in

the Interval

Vehicle Speed

Vehicle Length + Loop Size

∑

Calibrated Duration

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Wavetronix SmartSensor HD (101-0415) - User Guide Manual de usuario Pagina 68