[GIS] Formula to convert X/Y to Long/Lat coordinates of given point

coordinate systemlatitude longitudepointxy

I need to figure out how to convert my X/Y-coordinates to longitude and latitude.

I do not need the exact conversion, just an approximate so I can plot it in a mapping API. I managed to estimate the following X/Y to Long/Lat:

(x, y) = 24050, 123783.3333 -> (long, lat) = (122.98, 24.46)

(x, y) = 24216.6667, 123933.3333 -> (long, lat) = (122.985339,
24.46041)

Can I somehow use these to come up with a formula to convert the other X/Y points?

I found another link that does what I want, but I cannot extract the formula: http://www.whoi.edu/marine/ndsf/cgi-bin/NDSFutility.cgi?form=0&from=XY&to=LatLon

In the above link, I specify the origin of X/Y in Lat/Long coordinates, and it was able to convert X/Y to Lat/Lang.

Best Answer

It is complex, due to curvature of the earth effects and where on Earth you are.

I would recommend reading this page:

http://www.geosci.usyd.edu.au/users/prey/Teaching/Geos-2111GIS/Practicals/UTMConvDutch.xls

If you can replicate what the spreadsheet is doing in your API, you'll have your answer.

Exactly how you do that depends on the language you're using, and I presume you've got the programming skill to do that part.

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