Help me to find nearest latitude and longitude between a bunch of latitudes and longitudes

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BN 2020-1-26

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https://ww2.mathworks.cn/matlabcentral/answers/501995-help-me-to-find-nearest-latitude-and-longitude-between-a-bunch-of-latitudes-and-longitudes

评论： BN 2020-1-26

coordinates2.mat

Hello, I have a problem that I don't know how to fix it. It doesn't complicated problem but I can't solve it.

I have some station names and corresponding latitude, longitude and elevation. I want to find the nearest stations. In fact for each row, I need to compute the distance to all other rows and pick the one with the smallest distance. I want to save some computation by realizing that the distances are symmetric, and so need to compute only n*(n-1)/2 distances. I want to have the name of the nearest station together in a table to read them.

I attached coordinates2.mat

Here what I've done so far:

load coordinates2.mat
%start with one station:
Ahvaz = coordinates{5,{'lat','lon','station_elevation'}}; %Ahvaz is the 5th station in the list
coordinates(5,:)=[] %eliminate Ahvaz form list in order to pervent minimum distance going to be 0
All = coordinates{:,{'lat','lon','station_elevation'}};
%%compute Euclidean distances:
distances = sqrt(sum(bsxfun(@minus, All, Ahvaz).^2,2));
%find the smallest distance and use that as an index into All:
closest = All(distances==min(distances),:);
%result show me the lat,lon,and elevation of nearest station to Ahvaz,
% After that I should check list to find the name of it
%then should I clear and load coordinates2.mat in order to have Ahvaz again
% and check other stations

The main problem is this code isn't automatically changed over all stations. I should change it manually. also when the output (closest) achieved I should look at the list of the coordinate and finde match corresponding number by my eyes. I want to print the nearest stations in a table in order to analyze them in a more efficient way.

Thank you all.

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Answer 1

Mohammad Sami 2020-1-26

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https://ww2.mathworks.cn/matlabcentral/answers/501995-help-me-to-find-nearest-latitude-and-longitude-between-a-bunch-of-latitudes-and-longitudes#answer_412057

You can do it like this

dist = sqrt((coordinates.lon - coordinates.lon').^2 + (coordinates.lat - coordinates.lat').^2);
dist(dist == 0) = Inf;
[~,closest_id] = min(dist);
coordinates.closest_station = coordinates.station_name(closest_id);