Hi everyone,

I'm relatively new to both AFM and gwyddion, and my AFM is rather, well, 
non-standard (it's mounted on a spacecraft flying to comet 
67P/Churyumov-Gerasimenko as part of the ESA Rosetta mission).

Nevertheless, I'm trying to model our tip/sample interactions with our 
laboratory reference model, and need the tip radius as a result. We have 
MikroMasch TGX01, TGZ01 and TGT01 calibration standards on-board.

In any case, I'm enjoying using Gwyddion so far - it's great that a 
relatively specialised field as well-supported open-source application! 
But as a part of this process I have hit a few questions...

In running a blind tip estimation:

1. What does the "Use boundaries" option do? Does this respect 
previously marked grain/object boundaries, or something else? For one 
case I only get a sensible tip image using "Run partial" with this 
option checked. But when I tried a full run, still checked, it looked 
like the calculation would take several hours if not days.

2. Following on from the last - is there anything I can do to speed up 
the calculation? On a 85 pixel tip image of a 512x512 (~6µm×6µm) scan of 
the TGT01 "spikes", for example, I have just reached 27% of the first 
iteration after 1 hour.

3. Many of my fits results in a rather artificial looking central 
peak/spike - is this simply because I'm not using enough pixels for the 
estimated tip size?

4. I also have access to a copy of SPIP. I believe that the same basic 
blind tip algorithm is used in both, and yet the results are somewhat 
different (also, SPIP runs the same image as in 2. in ~30 s), and I'm 
wondering if anyone has an explanation for this?

5. One thing that SPIP does that would be super useful (to me at least!) 
would be to fit a curve/sphere to the tip and derive an estimated tip 
radius - is that something that could be easily added?

And a couple of more general questions:

6. Is there any way to overlay the pixel grid on a 3D image? I find it 
is useful (at least to me as a beginner!) to remind myself what the real 
image resolution is, and what is interpolated etc.

7. where can I see the basic image parameters (mainly number of pixels)?

Thanks in advance for your help!

Regards, Mark

-- 
Mark S. Bentley ([email protected])
Institut für Weltraumforschung (IWF), Graz, Austria
Phone: +43 (316) 4120-657, Fax: +43 (316) 4120-490
http://www.iwf.oeaw.ac.at/

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