19oct03
links to plots:
Survey2 radial errors arrow plot and fractional change.
image of survey 2 radial errors.
the normal error along each north/south column.
The median and rms normal errors along a north/south column of targets.
Motion of the target positions (survey2-survey1)  vs position on dish.
Magnitude of the target position motion vs position on dish.
The change in the measurement errors vs position on the dish.
Histogram of radial error ratio Surv2/Surv1.

     All 38000 targets were measured on mar01 (M_SUR1). After this the dish was adjusted. In oct-nov01 another set of pictures were taken (M_SUR2). These were measured and analyzed by the vstars software that came with the photogrametry equipment. The results became available in oct03. Lynn baker then fit a sphere to the targets and came up with a radial error for each target. For the plots below,  I took the two data sets and used only the common targets from both surveys (37752 common targets).
 


The coordinate positions of the targets.. How they've changed survey1 to survey2.  (top)

    The targets have  an x,y,z position using the center of the dish as the origin, x positive is east, y positive in north, and z positive is up.  There is an associated measurement error computed by the vstars software. The two plots below show how the coordinate position of individual targets moved between the first and second surveys.


The normal errors (radial direction) of the targets. (top)

    The radial errors are the residuals from fitting a sphere to all of the measured targets. The sign convention is: positive means the target is too far from the center of curvature, negative is too close to the center of curvature. The color bar at the top extends from -5 mm (blue) thru 0 error (green) to +5 mm (red). The black spots are missing targets.  I interpolated the x, y projected target positions  onto a grid of 3,1.5 feet using a tophat function with a radius of 3.4 feet. Some grid points have averaged together more than 1 target. The blue spots in the lower right stand out. They correspond to areas that were over corrected  (see fig 5). The red ring at a radius of 200 feet stands out clearly (the moat??). Some of the red horizontal lines that go across the entire dish are probably the new east west cables that were installed during the upgrade. They are probably stretching causing them to sink lower.


Normal errors moving along the north/south cable direction. (top)

    The panels are 3 by 6.25 feet and are mounted with the long direction east-west.  Targets are positioned at the corner of each target. As you look down on the dish, the targets make columns running north/south spaced every 6.25 feet (161 columns  in total). Every 25 feet a column of targets sits atop of one of the main support cables.
    I arranged the targets in columns of constant X by sorting the 38000 targets in X (east/west)   and then I found the locations where they jumped by 6.25 feet.  Each of these columns was then sorted in Y (north/south).
processing: x101/dish/M_SUR/dorsur1_2.pro
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