Hi Ruoyun, it seems that you are making a big effort understanding the tools of the area. Your ideas are more than enough to form a proposal. you should concentrate to make them more clear. Try to keep it simple and clear. Also regarding you English, I am not a native speaker to give professional advice, but also here try to make short sentences with simple English, in some parts it is not very easy to understand what you want to say, but in general I think you are passing the message. Looking forward to see your draft proposal. Best, Vissarion. On 27 March 2017 at 14:39, Ruoyun Jing <jingry0321@gmail.com> wrote:
Hi Adam and Vissarion,
2017-03-25 0:46 GMT+08:00 Ruoyun Jing <jingry0321@gmail.com>:
Hi Adam and Vissarion,
During these days I discussed the ideas of project 1 and begin to write my proposal. Here are what I learn about these project.
1.For the approach of compute the 3D cartesian distances first and if these numbers are not "far enough" then fall back to expensive geographic distance calculation otherwise return the result by comparing those numbers obtained by less expensive cartesian compuation.
The main problems is declare the "far enough". To figure out this problem, I would implement the method, test the result between function compare_distance and this method, then adjust parameter to limit deviation in an acceptable range(maybe it would be 1e-6 correapongs, the accurate value should be discussed by specific condition)
2.For the approach of perform a local spheroid approximation and return the 2D distance.
The main problem is to test the acceptable range of using spheroid approximation. The solution is same as answer above.
3.For the approach of getting 2 intersections of plane (which would be ellipse) with the help given points and compute the respective distances using those ellipses.
In my understand of these approach, it means we need to get cross-section through the center of ellipsoid and the geodesic segments. But I am not sure that the geodesic segments of two points whether can get a cross-section through the center of ellipsoid, and whether the cross-section is ellipse that we can calculate the sectorial area easy to compare. After check out the geodesic knowledge from differential geometry for a long time. I got some prove, but I think it isn't very reliable.
4.I have an reliable approach is that we could use the algorithms in "map projection" just like Lambert Conformal Conic, Gauss–Krüger projection, Mercator projection...etc,
Those projections make the point on 3D to 2D with reliable functions, although most of these projections use longitude and latitude, we could transform our cartisian coordinate into Spherical coordinate then transform them into longitude and latitude then use the projection to approximately calculate.
I read more about projection and we could use Local Cartesian Projection, one of the equidistant projection, which can provide ellipse and spheroid model.
All of above is what I discussed during these days, Could you please provide me some advise about them so I can strenthen my proposal?And if there has any problems about my poor English description please tell me, I will try my best to explain more clearly:)
Thanks all for your reading!
Looking forward from you.:)
Ruoyun -- Northwest University of China Software Engineering jingry0321@gmail.com
-- Northwest University of China Software Engineering jingry0321@gmail.com