Mapping geographic point coordinates to a coordinate grid - speeding it up

Hi all

I'm sure this must be answered somewhere but I'm struggling to find anything, perhaps because of my poor knowledge of the appropriate terminology. I have a set of geographic point coordinates (lat,lon) - these are my locations. I have a geographic coordinate grid (LAT,LON). I have a data grid, data = f(LAT,LON). I need to find and store the data for each point location. I have been using the 'distance' function in a loop, something like this:

for idx = 1:100

    % Calculate distance from a point location to each grid coordinate
    distDeg = distance(lat(idx),lon(idx),LAT,LON);

    % Find the mininum distance = correct grid cell index
    gridIdx = find(distDeg==min(distDeg(:))); 

    % Use the index to obtain the data for that location                       
    locData(idx) = data(gridIdx);

end

Is there another way that does not require a loop, or perhaps a function in the Mapping toolbox that could, for example, create a raster array (same size as LAT,LON) from my point coordinates that I can then use to index into my data array? I tried using vec2mtx but I still need a loop as it wants to treat vectors of point coordinates as a polygon, unless I'm missing something (probably). Any help would be much appreciated.

[José-Luis]

I am not sure I follow. Do you want to interpolate a grid from a series of coordinates with data.

In that case, maybe griddedinterpolant() is something that could help you.

[Eebs Ebola]

Hi there. No, I have a set of scattered data points in space. I also have a regular coordinate grid, and I want to quickly find the grid cell that contains each point. Thanks.

Answer 1

[Chad Greene]

Eebs, Is your dataset regular? By that I mean, is it a bunch of scattered points, or do your data points already fit nicely into a regular grid? If your data points are regular, there's no need to interpolate. Just use grid2xyz in the form:

locData = grid2xyz(lon,lat,data);

[Eebs Ebola]

Hi there. My dataset are not regular - they are scattered points. Thanks.

[Ananya Ray]

looking for an answer. I am calculating satellite coverage. so i get a lat long of a point on earth and a predefined lat-long grid. I need to know which grid point is the closest match.