After completing some recent GPS accuracy comparison tests between the Oregon and Colorado I thought it would be interesting to compare the two GPS units with WAAS/EGNOS enabled. Almost immediately I ran into issues. As noted in the Oregon Wiki Issues List I’ve observed problems with the Oregon acquiring WAAS/EGNOS.
This morning I watched more closely as the Oregon hunted for WAAS satellites. Here in the northeast US the order it searches satellites is 51, 33, 48, 35 followed by a sequential search of 33, 34, 35, 36, 48, 49, 51. The first four are the only WAAS/EGNOS satellites with high enough elevation for me me to get a reliable lock. During the test I noted if the Oregon doesn’t lock to the satellite in about 1-2 minutes it moves to the next satellite in the order. If it does lock (indicated by a hollow bar) with the satellite it will try for about 5-6 minutes to use that satellite for WAAS (solid bar). In a cold start the Oregon takes about 5-6 minutes to complete this last step. That means if on the first pass if you miss the chance to lock you’ll need to wait for about 30 minutes before it comes back around to the same satellite! Much of this is location dependent but I’ve heard from other Oregon users who have experienced similar issues in different parts of the world.
My tip to Oregon users is to make sure you know the location of the best WAAS/EGNOS satellite in your part of the world and when you turn on the Oregon ensure that it has a clear view to that satellite for 5-10 minutes. If you don’t get lock the first time around it is probably worth restarting the GPS rather than waiting through it’s painfully long hunt.
WAAS on the Colorado works a little better but the problem seems to be long acquisition times. With a clear view of satellite 51 it took the Colorado about 5 minutes to acquire WAAS when cold, 1-2 minutes when it is warm. As a comparison the 60CSx in the same cold start situation will acquire WAAS in about 30 seconds or less.
One interesting side note: compare the Oregon and Colorado screen shots and notice how many satellites each is tracking. Like the 60CSx, the Colorado is a 12 channel receiver and can track 11 satellites plus one WAAS/EGNOS bird. Based on the satellite screen the Oregon tracks up to 14 satellites simultaneously (13 non-WAAS and 1 WAAS). Given that the Oregon’s Cartesio chipset is a 32-channel device I guess this makes sense. Does this provide any advantage for the Oregon over the Colorado? None that I’ve seen. According to the literature there can be a maximum of 15 GPS satellites visible at any time, looks like the Oregon has that covered.
- Oregon Software: 2.6, GPS 2.55
- Colorado Software: 2.7, GPS 2.8