1. UFOAnalyzerV2 (UA2) the key of accuracy
UA2 inputs video clip files and outputs meteor trajectories.
UA2 does following steps for each clip, almost automatically
1) Reference star recognition  magnitude scale, precise direction of camera
2) Pre-event video averaging  Background brightness of each pixel
3) Target recognition on each de-interlaced field
4) Trajectory pole computation and trajectory correction
5) Classification of the object
April / UFOAnalyzerV2

2. Other UA2 functions
- Profile making : FOV plate adjustment with parameter optimizer
- Clip file management : view (movie, frame, field), delete, move/copy
- Plot : Trail map, Ground map
- Utilities : time adjust, video file trimming…
Note: Upward compatibility of analysis has been kept since 2004.
Anyone can get better result by re-analysis using latest versions.
My treasure!
Complete 6 years Records of Tokyo1
April / UFOAnalyzerV2

3. How UA2 processes video images
De-interlace analysis
Background subtraction
FOV plate constants
Center of a object, Light-sum
CCD spectral sensitivity compensation
Magnitude
Trajectory plane computation
April / UFOAnalyzerV2

4. De-interlace Analysis
UA2 does de-interlace analysis.
NTSC or PAL video signal contains two images taken in a different timing. It should be analyzed individually.
Merit of de-interlaced analysis.
Doubles time resolution (samples)
-- accuracy increased especially
for short meteors (major of obs.).
Shape of luminescence becomes simple
-- accuracy of center position increased.
Note : De-interlace analysis does not reduce the vertical resolution directly. The effect is complex depend on the size and speed of the object.
an interlaced frame
de-interlaced two fields
(deleted lines are interpolated, for display)
April / UFOAnalyzerV2

5. Background subtraction
UA2 does background brightness subtraction on each pixel, using the average brightness of adjacent video frames . ( UFOCaptureV2 records video before the event at least 10 frames. )
The incremental brightness is used for center determination and light-sum computation.
April / UFOAnalyzerV2

6. FOV plate constants ( compensation of lens distortion )
UA2 uses 4th polynomial equation for the compensation of lens distortion. R = k4*r^4 + k3*r^3 + k2*r^2 + (1.0 – k4 – k3 –k2)*r
Where
R is corrected distance from optical center on aspect ratio corrected plane.
r is catalog based computed distance from optical center.
R, r is normalized as 1.0 at the horizontal edge
The parameter optimizer decides k2,k3,k4, FOV size, optical center offset, pixel aspect ratio, az, ev, rot at once.
April / UFOAnalyzerV2

7. Typical position determination accuracy = 0
Typical position determination accuracy = 0.3 pixel, for most of the lenses
April / UFOAnalyzerV2

8. Comparison with exponential equation
April / UFOAnalyzerV2

9. Center of the object, Light-sum
Procedure for moving object
Sets a minimum rectangle that covers the Hit (brightness changed) pixels.
Compute the weighted center position of incremental brightness, using background image.
Sum of the incremental brightness becomes Light-sum of the object
Procedure for stars
Compute the background level as average brightness of donut field between R and 1.5R (default R=5 pixel).
Compute the weighted center of incremental brightness above the level.
Sum of the incremental brightness becomes Light-sum of the star.
April / UFOAnalyzerV2

10. CCD spectral sensitivity compensation (Cataloged magnitude compensation for the CCD)
To avoid the influence of the color of ref stars in FOV, UA2 converts each star’s cataloged visual magnitude (Mv) to color waited magnitude (Mc) according to the CCD spectral sensitivity.
Mc = Mv + Bvf * (B-V)  Typical error of star magnitude : 0.5 Mag
Bvf = , (2V-B) Bvf = 0.0 (V mag) Bvf = 1.0 (B mag) Mc
Bvf = 0.28 (WAT-N100)
Light-sum of star
The best value
WAT-100N : 0.28
WAT-902H2U : 0.30
April / UFOAnalyzerV2

11. Magnitude
For all clips that contains more than 5 stars, p, q are decided by least square method.
Mc = p*log( L ) + q : L is the Light-sum of the stars
p becomes -2.5 naturally. ( as is the theoretical value).
The object’s magnitude is computed by this p, q, and its Light-sum.
( Note: The color of the object itself is not is not compensated. It can be done by spectral camera only. )
April / UFOAnalyzerV2

12. Trajectory plane determination
UA2 determinates trajectory plane by least square pole determination
Note: Begin and End vector should be modified to be precisely on this plane.
Pole determination by least square method
(pole vector can be got by solving this 3 variable 3 simultaneous equations )
April / UFOAnalyzerV2

13. Remaining Problems
Correct center determination for meteor with irregular shape.
Big fire balls that cause white out of FOV
Breakup bodies / afterglow / asymmetrical shape
Some part of luminescence covered by clouds or edge of FOV
Dashed trajectory by clouds
Magnitude measurement without ref stars
Where is the body ?
How ?
April / UFOAnalyzerV2

14. Summary / Comment
Current UFOAnalyzerV2 uses many new method to achieve the automated hi-accuracy measurement. But still is having many problems. There is possibility that future version will do better for past records.
The largest error cause in current video observations is the determination of the center of the object. 0.3 pixel is current limit ( It causes up to a few degrees of pole direction error for short meteors even using 60 degrees FOV lens. From this point, all sky lens never be recommended ).
Velocity measurement is specially difficult, differential operation is very sensitive to errors and meteor often has unusual shapes such as tail, afterglow, or explosions.
These errors can be compensate by statistical method of post processing.
If the measurement of angular velocity becomes precise enough, the radiant estimation from single observation will be possible.
April / UFOAnalyzerV2