Comparing GPS trace to a standard

Hey,

Ok so iv got a whole lot of GPS traces each of which consists of two vectors - latitude and longitude. Lets say I need to compare these traces to a standard trace that represents a path over which many of the traces were collected. There is variation of a few meters in each trace which correlates to a difference of one in the fourth digit of the minutes field.

for example dd.mmmm 58.057*8* < ---- difference of 1 here between trips

does anyone have any ideas?

at the moment im running each vector through a loop that checks that the trace passes through all of 5 points(these 5 points are being used to define the route). this is not very flexible nor efficient to say the least!

Answer 1

[Walter Roberson]

missedpoint = 0;
for K = 1:numkeypoints
  if ~any( abs(tracelats - keylats(K)) < 0.00015 & ...
           abs(tracelongs - keylongs(K) < 0.0015 )
    missedpoint = K;
    break;
  end
end

It would be probably be possible to vectorize the whole thing using bxsfun(), but the space required would counter-balance the execution time.

[Andre]

Thanks!Havnt got the chance to try it out yet but ill let you know if it worked when I do.

Answer 2

[Walter Roberson]

What format is your data in, character or numeric?

Does it matter where else the trace goes, as long as it goes through near the 5 key points in some order? Not checking the order would be faster.

[Andre]

The data is in numeric form.

It does not matter where else the trace goes as long as it passes through the 5 points in any particular order. a small amount of offset in the coordinates is expected and is allowable as it comes from variations in the gps position from multipath errors etc.