Ping Sonar range setting and the angle definition

[EliotBR (Eliot)]

Hi @yuki,

Note that:

@patrickelectric

With Ping360 you have access to the direct parameters to configure the sensor without any abstraction, making the sensor more powerful [than Ping Echosounder] and as result a bit more complex to configure.

@yuki

1.Is an effective range set in ping-viewer reflected when python code is executed?

Yes, assuming you don’t turn off the device in between (parameters are reset to the defaults when the device turns on).

@yuki

Can an effective range be set up in ping360.py?

The range per sample is determined by the sample_period, so the total range is determined by sample_period and number_of_samples, together with the speed of sound in the water you’re operating in (see here if you want to estimate it from vehicle data, and here for estimating salinity).

If you want to make a set_range function, it may be worth looking at how it’s implemented in Ping Viewer

@yuki

2.When I use ping360.py transmitAngle(x), does “x “ represent the angle from the direction sonar is facing? Also, is the center of the sonar’s orientation (X=0) the same direction as the triangle drawn on the bottom of the sonar?

The following information may be useful:

@EliotBR

A few gotchas:

1. the ping angles are measured in gradians, so the angle attribute is a value from 0 to 399
2. the ping360 zero angle is at the back where the penetrator is, so ‘forwards’ (the direction of the arrow on the bottom of the Ping360) is at angle 200 gradians
3. Sonar (and all time of flight sensors) measure the time it takes for the pulse to return, so while d_{sound} = v_{sound} * t_{sample}, the target is half of that: d_{target} = \frac{d_{sound}}{2}

The following function can be used to determine the target distance per sample:

def meters_per_sample(ping_message, v_sound=1500):
    """ Returns the target distance per sample, in meters. 
    
    'ping_message' is the message being analysed.
    'v_sound' is the operating speed of sound [m/s]. Default 1500.

    """
    # sample_period is in 25ns increments
    # time of flight includes there and back, so divide by 2
    return v_sound * ping_message.sample_period * 12.5e-9

@yuki

When X=40 and while looping, does the sonar scan from 0 to 39 and then circle back around without scanning to 0? (0-39 scan → rotate without scanning 40~399 → 0-39 scan → …)
It takes about 0.5s to return to 0.

Not certain what you’re referring to here.

If you transmitAngle(40) and then transmitAngle(0) it will go the shortest direction back to the target angle (0 in this case), and it won’t transmit or take samples until it gets to the target angle. If you want you can test that by sending transmitAngle requests for 40, then 0, then 200 - it will take longer to get from 0 to 200 than from 40 to 0.

If you’re referring to the auto-transmit section then

@EliotBR

auto_transmit is a part of the protocol specification, but isn’t yet available in Ping360 devices. There’s a new firmware that’s been tested somewhat internally, but it’s not yet public, and there isn’t yet a publicly available firmware updater either.

The “not released” state is documented for auto_device_data but apparently got missed for auto_transmit - I’ve added that fix to a pull request.