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OR F - ORientation search - full circle used

(8/25/97)

PURPOSE

Determines orientation between two auto-correlation functions. It can be used to determine the angle between two similar images lying in arbitrary orientations. Image dimensions must be powers of two.

SEE ALSO

OR [Orientation search - half circle used]
OR 3A [Orientation search - 3D, arbitrary center]
OR 3Q [Orientation search - 3D, Eulerian angles]
OR FM [Orientation search - full circle used, find > one peak]
OR M [Orientation search - find > one peak]
OR P [ORientation search - not power of two]

USAGE

.OPERATION: OR F X10,X11

[The optional output parameters X10,X11 specify register positions for the rotation angle and the value of the angular correlation peak found in this operation. X10 contains the rotation angle according to a 7-point parabolic fit.]

.INPUT1 FILE: ACF001
[Enter name of the file containing the ACF of the first picture, 64x64 or 128x128.]

.INPUT2 FILE: ACF002
[Enter the name of the file containing the ACF of second picture; dimensions must correspond to those of the first picture.]

.NO. OF RINGS, WEIGHT OVERRIDE(1/0): 5,0
[Enter number of ring segments to be used for orientation search, and enter '1' if the default weights and radii are to be overridden (see notes).]

.GRAPH FOR EACH RING? (Y/N): YA
[Indicate if a plot of the CCF in the RESULTS file for each ring is desired.]

If A was the second letter to the above question SPIDER asks:

.ENTER SCALE FACTOR: 1.2
[The scale facter overrides the automatical scaling in subroutine GRAPHO, which otherwise scales the graph to the range of 50 steps.]

If the weight override option is chosen, SPIDER then asks for the radii and weights:

.ENTER RADII: 20.,25.,30.,50.,54.
[Enter radii (as floating point values) for each ring, (up to 10 per line). CAUTION: you must use the decimal point, otherwise the program does not use the correct values!]

.ENTER WEIGHTS: 0.1,0.2,0.5,1.0,0.1
[Enter a weighting factor (as floating point values) for each ring (10 per line).]

[SPIDER computes the cross-correlation of equispaced data along concentric circles around the centers of the ACFs; the resulting one-dimensional cross-correlation functions are weighted and added together. The orientation graph (between -180 and +180 degrees) is printed to the RESULTS file, with the position of the highest peak indicating the angle where optimum match occurs. The position and accuracy of the peak are also printed. If option ".GRAPH FOR EACH RING?(Y/N):" is chosen, the CCF of each ring before weighting is printed out (use this option for tests only,

because one page is used for each ring in the printout). In addition, the rotation angle will be put into the temporary register if an output parameter X10 is specified. This can be used as input to a subsequent RT operation.]

NOTES

  1. Accuracy and computing time increase with the number of rings.

  2. Default weights are 0.1 for the first ring and 1.0 for all other rings.

  3. Maximum number of rings is currently 20. If a larger number is specified, the system defaults to 20. The default radii are a function of the image size and the number of rings chosen. For example, for a 128x128 image, the default radii are 4.8, 9.6, 14.4, ..., 48. if 10 rings are specified.

  4. The full plane is correlated.

SUBROUTINES

ORNTS, CRCSE1, CRCSEC, ORPKS

CALLER

UTIL3

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