%%%% This function takes nan values in a DEM and interpolates them into
%%%% real values

function dem = interp2d(dem,lats,lons);

dem(dem<-10000) = nan;
for i=1:size(dem,1)
    row = dem(i,:);
    row = interp1(lons(isfinite(row)),row(isfinite(row)),lons);
    rows(i,:) = row;
end
for i=1:size(dem,2)
    column = dem(:,i);
    column = interp1(lats(isfinite(column)),column(isfinite(column)),lats);
    columns(:,i) = column;
end

dem = round((columns+rows)/2);
if max(max(dem))==3748; dem(140:190,:) = round((rows(140:190,:))); end % exemption for Santa Maria
dem(isnan(dem)) = columns(isnan(dem));
dem(isnan(dem)) = rows(isnan(dem));