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ANALYSIS OF OVERLAPS
This appendix describes the process used to carry out the analysis of
spatial overlaps for use within the program's 'Analyse Data' and
'Strategy' options.
List of sections:
The Procedure
The procedure consists of the following stages:
- Generate Unique Data
- If not already done at this stage, the program generates the unique
data based on the true, undivided, cell using the algorithm used in the
quick analyses. The total numbers of unique reflections and acentric
pairs are determined.
- Predict Spots
- The spots are predicted within the requested oscillation range or ranges.
Each range, at this stage, is padded by the maximum oscillation angle to
be used plus a further padding of 3 degrees so that partially recorded
spots will be included for all the images to be examined including those
at the ends of the oscillation ranges. Spots in the cusp region are
excluded and not considered. The included spots are stored in a main overlaps
spot list which includes storage of the following data items:
- Indices
- Phi value
- Spot phi half width
- Spot coordinates
- Spot already measured flag
- Centric flag
- I+/I- flag
- Overlap flag 1: spot is within an actual non-padded phi range
and is spatially overlapped.
- Overlap flag 2: spot is within an actual non-padded phi range.
and is not spatially overlapped.
- For each oscillation angle ...
- Sort Spot List
- Sort the spots list in increasing order of the spot 'yd'
detector coordintes. Clear counts.
- Loop through Phi (oscillation) ranges ...
- Loop through images ...
- Extract those spots, from the main overlaps spots list, which will
be recorded on the current image and store them in the current image list.
The data items stored are basically the same as those
in the main overlaps spots list with an exta word which stores the
position index of the spot in the main list. The overlap flag 1 is
set if the spot is found to be spatially overlapped but the overlap 2
flag is not used.
The current image spots list is searched and spatially overlapped
spots are flagged (basically the same algorithm as used in the
rotation prediction function (RPF) routines used by ROTGEN).
For each spot in the current image spots list, whose central phi value
falls within the rotation range for the image, the spatial overlap
or spatially non-overlapped flag is set in the main spot
overlaps list. Note that this means that, as the images data are
accumulated spots may possibly be flagged as both spatially overlapped
and non-overlapped. Note also that it is assumed that any
spots flagged as non-overlapped can be regarded as non-overlapped from
a spot integration point of view and possible overlaps of parts of the
spots on adjacant images are ignored.
Accumulate counts of overlapped and non-overlapped spots for all
recorded spots.
For the current oscillation angle, sort the main overlaps spot
list on the unique indices and then gather the statistics for the
percentage of overlaps in terms of the percentages of unique reflections
and acentric pairs. A unique reflection is counted as non-overlapped
if it is non-overlappped on any of the images in which it is centred.
For an acentric pair, both the I+ and I- reflections must be present
as non-overlapped spots. The required results are displayed for the
oscillation angle in question. If using the standard set of oscillation
angles and 5% or more of the spots are found to overlapped, then no
more oscillation angles are examined.
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