Sonar gives wrong results?

[maillemaker]

So on my last career I survived long enough to get sonar, and I tried it out. I dialed the hydrophone until I had a target, and then I pinged it.

It returned a range.

But every time you click it, you get a wildly different, smaller value. Much smaller than can be accounted for by closing speeds.

I can click a dozen times in a few seconds and cut the range in half.

What gives?

Steve