[David Fort]

I presume this info is too late to be useful, but we found that the Vex ultrasonic sensor picks up chain link fence about 90% of the time if you are about 4 feet away from it and the incident angle is 90 degrees.

At 10 inches, it almost always doesn't see it.

We also used the Vex sonar in this year's FTC challenge QuadQuandry to find the post on the goal. We found you could see the post reliably (the cone angle on the sensor is pretty narrow - maybe 15-20 degrees, so we swept the sensor back and forth to find it).

We earlier tried to pick up the distance to the base on the FTC goal, but found it didn't see the surfaces when viewed from the vertex of the hexagonal base.

For surfaces orthogonal to the beam measurements up to 170 inches seem pretty good. (i think it could go further than that, but that is where 16 bits overflows on the Vex timer)