Averaging A Position With A 60 Csx

[+Captain Gore-tex]

Can someone post the correct method of averaging a position. I have followed the scant details in the manual and am not sure what the unit is doing when it runs through the request as the altitude seems to be changing whilst stood still.

[+El Diablo]

Hit your "Mark" button and then on bottom left hit the "Avg" button and let it go through its paces. I just did one that did 141 readings and got it to 20.2 feet estimated accuracey took it about a minute and that was with a lock on 5 sats. I was indoors when I took the reading so it will probably be more accurate outeside.

 

El Diablo

[+hurley_108]

When you're just looking at your position in real time, it changes because of various changing conditions, most of which is due to the varying time it takes for each satellite's signal to get through the ionosphere. These errors over time cancel each other out. This is what Averaging does. It takes a number of readings of your position (you can see the count go up), and averages them together, yielding a more accurate result.

 

The altitude changes, because altitude is very inaccurate, so teh difference between the average altitude, and the altitude you started from will be very different. As the count goes up, you should see that number settle down, of only because each new reading can't change the average very much.

 

I've found that 100 readings almost always gets me to within 3m of true position (tested against benchmarks), and 400 is even better. I usually do 400 when I'm placing a chache. Nobody's had problems with my coords! =]

[rbrugman]

I went down to the beach the other night and averaged until 500. I got the estimated accuracy down to 3.4 feet. That's the lowest I've ever seen my 60csx go.

[Hertzog]

Can someone post the correct method of averaging a position. I have followed the scant details in the manual and am not sure what the unit is doing when it runs through the request as the altitude seems to be changing whilst stood still.

As hurley_108 mentioned, the altitude - and the lat/lon as well - will change as the averaging takes place. But another thing that happens with altitude is that the 60CSx uses the barometric altitude when you initially mark a waypoint, but changes to the GPS solution altitude when averaging the waypoint. So if you happen to have a substantial difference between the barometric altitude and the GPS solution you will see a sudden jump in the altitude value when you start the averaging.

[+hogrod]

I was wondering how good the average feature was with my 60cx so I decided to test it the other day. About 6 times over a 24hour period I would mark 10 waypoints in the same location(over about 10-15minutes) and also average the spot for 2 readings each time(100 point average). I would name the averaged with an A followed by a number so I could tell which readings were averaged.

guess what, about 70% of the averaged readings were outside edges of all the readings I took, with a large cluster of readings in a 20ft circle. I took one of the center most readings because I would think this was the most acurate.

 

I should also say when I put my averaged coords into the legendC and did a goto it thought I was north of coords about 30ft when in reality I was south of them 30ft, it took the legendC about 5minutes to figure out it was wrong. doing a similar test later with the 60cx it also wasn't right at first but corrected itself in just over a minute.

 

This test was done indoors because I wanted it done in a poor signal enviroment. I can now find my couch with a high degree of accuracy!