This is a simple technique that doesn't require expensive equipment and it is safe to do.
The known reference object needs to be directly below the wire for this to work. If you are not directly below the wire, then there will be distortion in the proportionate measurement.
You can also use a traffic cone or some other object like a person.
Cone height = 1.1'
Measure to the top of the cone = 7 units
Measure to the overhead wire = 165 units
) Height of wire = 165 x 1.1' / 7 = 26 feet.
If you have a ground elevation you just add the height to get the elevation of the wire.
Ground Elevation =1231.73'
Wire Elevation = 1231.7' + 26' = 1257.7'