Jixie and I went into hall to take another measurement, trying to get a reference point which is in the survey data. The beam pipe was taken off, so we measured the bpm2 to the post mount Karl and James measured last time. We are not sure about the exact measurement point of the survey, so two sides of the bpm2 were both roughly measured. First is 67mm, second is 92mm. 67mm plus 23 9/16 " gives 665.5mm, comparing with 676mm in the survey data. James said the survey did not care too much about z direction (tape measurement), so I guess 1cm is a reasonable result. He will get clear of the exact measurement point and get back to us later.