# Boost :

Subject: Re: [boost] [gsoc17]The implement of Programming competency test From Ruoyun Jing
From: Ruoyun Jing (jingry0321_at_[hidden])
Date: 2017-03-27 11:39:08

2017-03-25 0:46 GMT+08:00 Ruoyun Jing <jingry0321_at_[hidden]>:

>
> 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, Gaussâ€“KrÃ¼ger 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:)
>
>
> Looking forward from you.:)
>
> Ruoyun
> --
> Northwest University of China
> Software Engineering
> jingry0321_at_[hidden] <jingry0321_at_[hidden]>
>

```--
Northwest University of China
Software Engineering
jingry0321_at_[hidden] <jingry0321_at_[hidden]>
```