Thursday, July 22, 2010

GPSMAP 62S vs. Oregon 400i

I got the 62S for two main reasons. With age, near sightedness is a problem, and it is hard to rely on reading glasses in the woods. So I needed a better display than my Oregon 400i could offer. While the 62S has a lower resolution than the Oregon 400i, that lower resolution seems to make it easier for me to read it, and the brightness of the display is helping too, so that problem (of mine) had been addressed.

The 3-axial compass is easy to calibrate, easier than my Droid Incredible, and once that done, it is a pleasure to use, no more trying to level things out. Beautiful. Compared between the two and my trusted Brunton Eclipse and had the same results, all three compasses indicating magnetic north where it should be.

I tested both units on the road near my house, a complete square shaped circuit, mostly in the open but the south side, especially on the outside of the road comes next to tall trees in full foliage. First time around, I walked on the inside, clockwise. The second time around, I walked on the outside, still clockwise and I reversed the GPS position.
At first, in the open, I noticed both units being very close in numbers, in single numbers even, sometimes just a foot away from each other, well they actually were, as I held one in each hand! But further down the separation grew to six feet, the 62S always being the best. I had WAAS acquisition, quite strong on both units, satellite 48. I lost it for a brief moment on the southern leg on the Oregon, but it came back. Now on the second time around, still on my east leg, I noticed the Oregon becoming less precise, much less so than the 62S. I also noticed the WAAS reception was not so good on the Oregon and it was on satellite 33, whereas the 62 was on 48. I lost WAAS on the southern leg on the Oregon, while I did not on the 62S. Precision went down to about 18ft on the 62S but was double that on the Oregon at nearly 40ft. I was watching the satellite screen all the time on both units.

So how do the track look and compare?

On the left, the Oregon 400i's screen and on the right the 62S.

You can see that the scale is different as going to 120ft did not allow to have the entire picture on the 62S' screen.OTOH, on the Oregon at 200ft the two tracks almost blended, due to the higher resolution, I guess.

I would have been very pleased with either, as they show me on the correct side of the road, and this is not a major thoroughfare, mind you.

Look at the NW corner. On the outside, I had to decide when to cross the street and the way I crossed is better shown on the 62S than on the Oregon 400i. Looking at the SE corner, on the outside, I had to leave the edge of the road as it was overgrown there and the 62S shows it a bit better. Really, I am nit-picking, yet the 62 is the winner!
The maps displayed are not the same. The Oregon has Topo 2008 and NY 1:24000 topo that is displayed, whereas the 62S had the Garmin 1:24000 NE on a uSD card.

I will now put those tracks on an aerial in TopofusionPro and see if the win stays with the 62S.

OK, now we are talking magnification (click on the picture is you need to see it larger) and I see nothing further to add. The two units are darn good, with victory by points to the 62S because it tracked me more accurately in those corners and its WAAS fix was much more stable.

I was tempted to dig up files from the past, but then I remembered that GPS constellation would be different and also the GPS software and firmware would not be the same, thus introducing uncontrolled variables, so I'll stay away from that.

This is a work in progress, I'll add more as I do more. For now both units will accompany me in my forays, but I have a very sound feeling about the 62S. Scott from GPSFix fame told me he had tested the 60csx vs. the 62S and the display of the 62 is at least as good if not better than the 60csx because of the added colors. And his eyes are better than mine, I believe, certainly not as old.

I remembered I had a Gilsson external amplified antenna which I had not used since I got the Oregon. I found it nevertheless and since today is a rainy day, all I want to do is indoors testing. So here are the screens:

Left is with the Gilsson external amplified antenna, right naked 62S, same location, well read the UTM! I am indoors BTW. Location is as correct as I can place it on an enlarged aerial, altitude is right too, the only difference is the GPS precision circle and stronger reception of the satellites in general with the external antenna. Notice that WAAS is working fine (full bar with the external antenna) but I'm not far from a window. IMO, for SAR work, I don't see the need for the external antenna. I'll put it in/on my radio harness, to be used if conditions ever necessitate it, but not as routine use. I also noticed that the MCX connector is quite difficult to detach. I even used needle nose pliers.

Scott (GPSFix/wikis) had trouble transferring tracks adn Geocaches wirelessly. I tried too, from the Oregon 400i to the 62S and although both units indicated transfer completed 100%, I could not access these tracks on the 62S. Now upon checking via computer, I can see those files in the GPX folder! I have just restarted the 62S, still no-go! We may have a minor bug there!

The 62S at its worst!

I left my 62S on by my keyboard at my desk. I don't remember what I did check, but I forgot the unit on for just over an hour. Now my shack and computer are in the basement, facing a wall that is below ground. Behind me are stairs and the living room and only part of a window is visible, double pane glass, window treatment and behind it there is a huge tree in leaf. Most GPS units have no reception here, maybe if I hold them up so they have a better angle at the window and the satellite geometry is just right, but in most cases, I have no reception. Well, I have a track of 148 points, .52 miles long, my 62 being set at marking a point every 5 yards!

So here is the display on the 62S' screen:

And here on TopoFusionPro:

Well I measured the total deviation, north-south was 70 meters and east-west was 50 meters.

Frankly, I've seen much much worse from earlier Garmin units. Why did my 62S do that, simply the signals from the satellite were bouncing all over the place, my below ground wall being just two feet from the 62S, as well as my desktop computer and HF radio and other ham gear. I always like to know how my equipment will function in extreme conditions and although I did no set up this test, the results are interesting and actually, IMO quite good. Tomorrow, I'll leave the 62S in outdoors for a hour and we'll be able to compare results. Satellite geometry will be different but the placement should give it quite an advantage.

OK, so today, I left the OR400i and the 62S on the table on my deck, is good position to acquire satellites for over an hour and a half. Here are the results:

Screen size tell you which is the OR and which the 62S (ok the latter is on the left). Well, both did well, both in a 20ft diameter circle. Length of the "track" was different, maybe due to the extra sensitivity of the 62s' antenna? Now I did not take a screen dump of it but under a more normal working scale like 120, 200, etc. you can't even see that drift on the screen. Now for those of you who are looking for a 35mm film canister (Geocachers), you need to search for it in 314 square feet, a circle that has a radius of 10 feet.