[Proj] How to obtain (lat, lon) of a point if I know a reference point and relative distance (km)?

[Zhuanshi He]

Dear All,

I want to obtain (lat, lon) of  a serials of points saved in a data
file. Before do that, I need to know how can I do it for one point.

The pionts came from Mecartor projection. Now, I have a reference
point (reflat, reflon), and the distance (kilometers) (x,y)
corresponding to same (reflat,reflon). How to calculate the unkowns
(?lat.?lon)? Can proj do it?



 ---(Reflat,reflon)-----------------(x)---------
              |                                   |
              |                                   |
              |                                   |
              |                                   |
              |                                   |
--------- (y)-----------------  ?(lat,lon)---------


Many thanks for your help.


-- 
Zhuanshi He / Z. He (PhD)
ADvanced Environmental Monitoring Research Center (ADEMRC)
Gwangju Institute of Science and Technology
1 Oryong-dong, Buk-gu, Gwangju 500-712, Republic of Korea.
Tel. +82-62-970-3406   Fax. +82-62-970-3404
Email: Zhuanshi.He at gmail.com
Web: http://atm1.gist.ac.kr/~hzs/