Hi Vissarion, 2017-03-20 20:29 GMT+08:00 Vissarion Fisikopoulos <fisikop@gmail.com>:

Hi Ruoyun,

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- The main work I should do during GSoC about project 1 is just to improve the algorithms of compare two distances of two point pairs or try to consider different situations which used compare distance predicates to avoid calculation?

the project is about algorithms that does not compute the actual distance but an approximation (as rough as possible) that suffices to accurately compare the lengths of two geodesic segments on the ellipsoid

Thanks for your answer, I have the correct point of these project and will continue to write my proposal.

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- Do "In some algorithms there is the need to compare two distances of two point pairs" this means compare two points distances on Earth? Or on every ellipsoid model?

the later (see answer above)

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- Do I need to find the approaches of filter by myself? Could you please help me get more information about these? Like the implement detail about the predicate compare_distance function, mathematical calculation papers about compare distance on ellipsoid?

Well we give one approach on the website (there is another proposal of another candidate on the list). My opinion is that if you understand these approaches (pos and cons, differences etc) that will help you towards a solid application. Having another idea for an approach will definitely strengthen you application.

Thanks for your help. I can get the point of those approaches and will try to have new ideas. :)

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- In my view, just like compute the shortest distance between two given points on Earth, the background approach can be used. And I used cartisian coordinate to avoid many trigonometric function calculation, but I can not find more improve with my lacking knowledge, could you give me some aspects to get more approaches?

Please see answer above

At this point I think it is better to jump to boost list because our discussion could interest more people. I will not copy anything of our private conversation there but feel free to do the jump and I will continue answering there.

Btw, any news from you test and comparison with Boost.Geometry.

I reply you and jump to boost with your advice. Hope this will help more people. :)

Vissarion

ps. you can send questions whenever you want, I will answer them a.s.a.p. my zone is UTC+2

Thanks for your answer.

Best regards. Ruoyun -- Northwest University of China Software Engineering jingry0321@gmail.com <jingry0321@163.com>