MATLAB Answers

## Calculating the greater circle distance from source point to centre of all grid cells in a domain/reference grid

Asked by Charlotte Findlay

### Charlotte Findlay (view profile)

on 18 Jan 2019
I am trying to calculate the greater circle distance in metres from a source point (specified as a latitude/longitude) to the centre of all grid cells within a domain (or reference grid - calculated using makerefmat).
Would anyone be able to help me with this?
% Source point location (decimal degrees)
sourcelon = -7.340612;
sourcelat = 57.005755;
% Reference grid
% Domain size
DDX = 4800; % Varation in the domain size for X
DDY = 5760; % Variation in the domain size for Y
% Define limits of latitude and longitude for the area of interest
latlim = [53.5, 59.5];
lonlim = [-9, -4];
% Create vectors of latitude and longitude which are divided by the same
% interval sizes as the domain
latvec = linspace(latlim(1),latlim(2),DDY);
lonvec = linspace(lonlim(1),lonlim(2),DDX);
% To define dy and dx, divide the initial latitude minus the final latitude
% (or longitude) by the number of elements in the domain array i.e.DDX or DDY
dy = abs(latlim(1)-latlim(2))/DDY; %dy = difference in latitude (y) between pixels in successive rows
% (degrees)
dx = abs(lonlim(1)-lonlim(2))/DDX; % dx = difference in longitude (x) between pixels in successive columns
% (degrees)
% Specify the coordinates for the left hand corner of the map domain
x11 = lonlim(1);
y11 = latlim(1);
% Create the referenced matrix grid (R)
R = makerefmat(x11, y11, dx, dy);

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