[Non-Sequitur]

ATC radar uses mathematical algorithms to eliminate ground clutter.

Then how did it happen to pick up surface contacts in this case?

[ml/nj]

Then how did it happen to pick up surface contacts in this case?

I wondered about this too, but it's clear that they did. It probably has to do with whether the undesirable data is actually discarded when it is filtered out.

ML/NJ