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avoiding "projected" weight maps
07-24-2008, 14:42
Post: #1
avoiding "projected" weight maps
The swarp manual mentions that upon image resampling, projected weight maps are created which will later be applied in producing the combined output image. This is the case even when WEIGHT_TYPE is set to NONE. However, the approach to use a normalized background variance as weight only works well if the background noise can be estimated for sure. While dealing with a field towards the Galactic center with dark clouds in the foreground, I noticed that the weights differ by a factor of ten between various tiles although the images were taken under photometric conditions. Obviously, in very crowded fields noise estimation is difficult. Since there is no switch to turn off the internal weighting, input weights maps set to 1/sigma^2 can be used to end up with an almost uniform weighting (small deviations result from differences between the noise estimators of SWARP and mmm.pro in my case) .
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10-23-2008, 15:42
Post: #2
RE: avoiding "projected" weight maps
Very good point. I take notice for a future version.
Thanks a lot.
- Emmanuel.
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