When in Map View (L button), enter the coordinates with the search button. There should be a tone to indicate you are in the correct area, just look around the screen for the hidden traveler.

Effect	Code
Secret 1	-23.442896, 151.906584
Secret 10	63.735797, -68.515134
Secret 11	28.52346, -80.642406
Secret 12	-34.829096, 20.009499
Secret 13	55.577629, 12.815806
Secret 14	51.178946, -1.826564
Secret 15	28.007168, 86.86105
Secret 16	30.740941, 104.139226
Secret 17	48.872153, 2.295303
Secret 18	-22.913247, -43.196263
Secret 19	38.897633, -77.036762
Secret 2	34.969327, 135.757025
Secret 20	57.324384, -4.442323
Secret 21	-22.951895, -43.210295
Secret 22	33.753227, -118.190757
Secret 23	34.297206, 132.318139
Secret 24	27.173322, 78.041434
Secret 25	37.802197, -122.418946
Secret 26	34.382853, 133.819175
Secret 27	13.41186, 103.864023
Secret 28	43.080032, -79.074482
Secret 3	-62.59574, -59.901784
Secret 4	40.758609, -73.98507
Secret 5	1.286587, 103.854408
Secret 6	13.759204, 100.49668
Secret 7	21.273054, -157.823806
Secret 8	-17.829978, 25.118641
Secret 9	25.197184, 55.274378