More MDS testing

Note there are three other Durham MDS pages, Durham_MDS_Testing, Durham_MDS_Testing3 and Durham_MDS_Testing4.

Investigating the convolution of MD08 Stack 041 (Peter Draper)

The small scale structure seen in some of the stacks is highlighted in the following image:

This is a very small part of the 041 skycell stack from MD08 re-created at Durham from the released warps. Looking at the intermediary convolved warps during processing you can see that this small-scale high frequency mottling is already present, so this must be an artifact of the convolution not the combination.

The representative kernels used to convolve the warps are found in the third extension of the .kernel files, and look like this:

Collapsing the data of the kernel along the X and Y directions and taking a single pixel slice, shows the small-scale structure responsible for the mottling:

Note that convolving an image outside of IPP with this kernel confirmed it is the source of this effect.

Improving the stack, aka removing the mottling

Inspecting each of the skycells that contribute to the stack shows a range of imperfections, some are quite serious, like double images and others less so, like trailing and low signal. In general the image quality isn't good, with most images displaying some irregularities.

To improve the stack and see what effect this would have on the matching kernels I removed the images judged to be badly trailed, had double images or little signal, and re-stacked (removing 6 of 23 images). This gave the following results. For comparison the before and is shown again below the after.

---

---

---

---

---

It is immediately obvious that the mottling effect has been suppressed and that the matching kernels are somewhat less irregular, although still not symmetric or monotonic. This result must raise questions about the selection of warps that are selected to create a stack.

The latest IPP stacking software is investigated on Durham_MDS_Testing3 and Durham_MDS_Testing4.