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Understanding the Ping 360 specifications

Hi, i’ve finally gotten my hands on a Ping360! I am currently working out how to understand the specifications of the device. I will be using the data for complex navigation. I therefore have some quite specific (and technical) questions:

The device has a range resolution of 0.08%. I am a bit usure how to interpet this. A 50 m, this gives ca. 4 cm. Does this resolution make it impossible to tell and object that is 47 meters away from and object that is 50 meters away? Or is this the resolution slant range. I.E if two objects are 3 cm away from each other and both are 50 m away from you, then you can’t tell them apart.

Basically: what can you define the resolution in terms of polar coordinates?
Is the angular precision better when combining measurements? I notice that the mechanical resolution is 0.9 deg, while the horizontal beam is 2 deg.

Why is the scan speed different at 2 m than at 50 m? Wouldn’t the sonar scan for all ranges (2-50 meters) at all times? And wouldn’t that imply a constant scan speed? Or can i somehow limit my range to 2 meters to improve scan speed?

Third, does the vertical and horizontal bandwidth define the size of the slant angle?

And lastly: is it possible to get some data on the measurement noise?

Best,
Ole

The device has a range resolution of 0.08%. I am a bit usure how to interpet this.

The sonar works by emitting an acoustic pulse, and then sampling the return signal intensity over time at regular time intervals. The ‘range resolution’ is determined by how frequently the signal is sampled for a given time interval. Shorter sampling periods = more samples = greater resolution. If you take 100 samples in the time that it takes sound to travel and return 10 meters, then your resolution is 10 meters/100 samples = 10 cm / sample.

The sonar can take up to 1200 samples per pulse, so we have given a range resolution of 1/1200 = 0.08%. At 50 meters, that equates to 3cm distance between each signal sample. This affects resolving objects in front/behind each other, as opposed to objects beside each other (that would be angular resolution).

Is the angular precision better when combining measurements? I notice that the mechanical resolution is 0.9 deg, while the horizontal beam is 2 deg.

I’m not sure how to answer this, but my experience with math and statistics tells me it’s probably possible, I just don’t know how.

Why is the scan speed different at 2 m than at 50 m? Wouldn’t the sonar scan for all ranges (2-50 meters) at all times? And wouldn’t that imply a constant scan speed? Or can i somehow limit my range to 2 meters to improve scan speed?

It takes less time for the acoustic pulse to travel 2 m than 50m, the amount of time where the sonar is sampling the return signal is limited at 2 meters to improve scan speed.

Third, does the vertical and horizontal bandwidth define the size of the slant angle?

And lastly: is it possible to get some data on the measurement noise?

I can’t answer these last two, but I’ll refer you to our scanning sonar guide, and ping @kklemens and @rjehangir who might be able to help.

The stepper motor we use in the Ping360 has 400 steps per full revolution. 360/400=0.9 degree mechanical resolution.

The horizontal beam of 2 degrees references the acoustic beam pattern as denoted here: Acoustic Beam Patterns

So it will rotate in finer increments than the acoustic beam pattern.

does the vertical and horizontal bandwidth define the size of the slant angle?

The slant angle/range is to a target within the beam pattern. Vertical Arrival Angle and Slant Range.

Is it possible to get some data on the measurement noise?

Can you explain what you’re looking for here a little bit more? We have a sample scan file under the “Learn” section of the product page: Ping360

Hi, thanks for a great reply. Quick question:

The slant angle/range is to a target within the beam pattern.

What do you mean by this?

Can you explain what you’re looking for here a little bit more?

I need to develop an understanding of how the motion of the sonar affects the sonar output. The ’ Understanding and Using Scanning Sonars’ page gives some background on this but no mathematics.
I would be very interested in some mathematical formalization about how rotation and translation affect the quality of the sensor output.

E.g. say the sonar transmits a wave. In the meantime, the AUV (and the transducer head) is rotated due to some disturbance (e.g a wave). The returning wave then hits the sonar at a new angle. Does the sonar still return a valid output? How much can i rotate and still return something valid? Maths, please!

Note that i will probably not be using the ping viewer and will make something custum. Image smearing is not my main concern here.

The sonar can take up to 1200 samples per pulse, so we have given a range resolution of 1/1200 = 0.08%. At 50 meters, that equates to 3cm distance between each signal sample. This affects resolving objects in front/behind each other, as opposed to objects beside each other (that would be angular resolution).

So is this resolution determined by:
A. The given sampling period. I.e the range that sonar is currently using. Then every measurement from the sonar has the same resolution. E.g if the range if i get a measurement of 2 meters and one of 50 then they have the same resolution.
B. The range of the given measurement. E.g if the range if i get a measurement of 2 meters and one of 50 then they have different resolutions.