protected int compress(boolean[] inFlags)
	{
		int numPoints = _track.getNumPoints();
		int numDeleted = 0;
		// Loop over all points looking for duplicates
		for (int i=1; i<numPoints; i++)
		{
			// Don't delete points which are already marked as deleted
			if (!inFlags[i])
			{
				DataPoint currPoint = _track.getPoint(i);
				// Don't delete any photo points or audio points
				if (!currPoint.hasMedia())
				{
					// loop over last few points before this one
					for (int j=i-NUM_POINTS_TO_BACKTRACK; j<i; j++)
					{
						if (j<0) {j=0;} // only look at last few points, but not before 0
						if (!inFlags[j] && currPoint.isDuplicate(_track.getPoint(j)))
						{
							inFlags[i] = true;
							numDeleted++;
							break;
						}
					}
				}
			}
		}
		return numDeleted;
	}