Find the closest location in an array of latitude and longitude

[koukileo]

 I have a geographical array, and I want to find the closest geographical location based on a given latitude and longitude. For example, if I provide 121.830, 25.1, it should be New Taipei City, Ruifang District. Can someone give me some tips or assistance?

chatGPT said that  can try the following method

[billko]

Why don't you further refine it and add "do it in LabVIEW"?

[koukileo · Accepted solution]

I just solved this problem. I calculated the distance between two sets of latitude and longitude coordinates and found the location with the shortest distance in the array, which is the geographical name closest to the target latitude and longitude.

[JÞB · Accepted solution]

Since you are merely interested in proximity and not actual surface distance you can easily solve for the Chord Length between each point in your array and the chosen location.

Chord Length=((dX^2)+(dY^2)+(dZ^2))^0.5

See here for calculating dX, dY and dZ

It's a simple matter the to solve for the chord angle given Diameter = 1 unit Earth and convert to radian Length across a flattish surface with +/-%0.5 accuracy.   Surface distances in the Himalayas will vary more than over calm seas.

[koukileo]

that's a good idea!

[koukileo]

You are right, I should have tried it myself on labview instead of asking first. thanks for your teaching

[JÞB]

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@koukileo wrote:

You are right, I should have tried it myself on labview instead of asking first. thanks for your teaching

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Altenbach is sure to post an example using Polar to Complex and simple subtraction to get dTheta and dPhi.  dRho=0 assuming both points are near sea-level.

[billko]

Darn, I was hoping to see what ChatGPT was going to say about it.  😄