How to select data with identical lat lon from two large matrixes ?

I have been working with the satellite data. So I have exported two matrices in matlab which contains nearly 230000 and 370000 rows and 3 columns respectively. The first 2 columns are latitude and longitude and next columns contain readings. what should I do to select the data so that out put is a matrix with latitude and longitude and next two columns gives reading for matrix 1 and 2.

M-1  Lat  Lon  Reading     M2  Lat  Lon  Reading
  23  56  1    24  58  3
  24  58  2    25  54  5
  26  59  3    27  58  6
  22  57  4    23  56  9
  25  54  5    26  59  8
  29  51  6    30  60  4
  22  52  7    23  54  2
  21  50  8    22  56  3

Result  Lat  Lon  M1  M2
  23  56  1  9
  24  58  2  3
  26  59  3  8

Thanks, in advance

Answer 1

[Walter Roberson]

M1LL = M1(:,1:2);
M2LL = M2(:,1:2);
[M1inM2, M2idx] = ismember(M1LL, M2LL, 'rows');
joinedM1M2 = [M1(M1inM2,:), M2(M2idx(M1inM2), 3)];

[amberly hadden]

Thanks, Walter but output is an empty matrices

[amberly hadden]

My be its a rounding error ? as when I applied it to roigonal data set the output is an empty matrix.. I'm trying to round the digits to two decimals and then apply it. Thanks