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GPS Accuracy


psyber7
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Hello,

 

Garmin states that with WAAS enabled the the accuracy of the GPSr should be within 3 meters (10 feet), I have yet to find this to be true. I think the most accurate I got was within 30 feet of accuracy as displayed on the unit. Has anyone else had accuracy issues with the 60CSx?

 

Some times when I'm searching out a cache, it will tell me 20 feet in that direction then I take a step or two towards that direction and it switches direction and changes the distance to the waypoint. It acts as if there is some interfering object (electro-magnetic) nearby, by the way the compass needle revolves around the compass.

 

I've tried this in different areas it's not that I'm trying this under High tension wires [:laughing:]

 

Are there any ways to improve accuracy?

 

Thanks,

-psyber7

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Are you saying that you've never seen less than 30' accuracy? How many satellites are you receiving and do you see a WAAS signal - (Sat above 32)? Do you have D's displayed on the bars for the regular Sats?

 

I get 20'-30' inside my house! Yesterday, I was getting 27' under a heavy tree canopy. Routinely in an open area, I get 10'-12'.

 

Once you get within the circle of accuracy, it is not uncommon for the compass needle to rotate randomly. That is to be expected because the unit thinks you are at the destination.

 

Do you have trouble with automatic watches keeping time? Are you keeping the unit in a location near your upper body and not stuffed in a packet or a backpack?

 

What kind of accuracy do other folks with GPS's receive in your area?

 

Although I don't use one, I understand a good quality external antenna improves accuracy a little, but you're not in the ballpark of what you should be getting. Is there anything else we're missing here that I haven't mentioned?

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Are you saying that you've never seen less than 30' accuracy? How many satellites are you receiving and do you see a WAAS signal - (Sat above 32)? Do you have D's displayed on the bars for the regular Sats?

 

I get 20'-30' inside my house! Yesterday, I was getting 27' under a heavy tree canopy. Routinely in an open area, I get 10'-12'.

 

Once you get within the circle of accuracy, it is not uncommon for the compass needle to rotate randomly. That is to be expected because the unit thinks you are at the destination.

 

Do you have trouble with automatic watches keeping time? Are you keeping the unit in a location near your upper body and not stuffed in a packet or a backpack?

 

What kind of accuracy do other folks with GPS's receive in your area?

 

Although I don't use one, I understand a good quality external antenna improves accuracy a little, but you're not in the ballpark of what you should be getting. Is there anything else we're missing here that I haven't mentioned?

 

Okay, here's the deal. I just walked outside and I was getting an avg. accuracy of 68 feet (receiving anywhere from 4 to 7 sat's, under cloud coverage) in which none of them are labeled higher than 27.

 

I came back indoors and I am now receiving an accuracy of 24 feet with six sat's locked on (at this very moment) in which the highest satellite is labeled # 26

 

Does this mean that I am not getting a WAAS signal? Furthermore, why would I get better accuracy indoors than outdoors? Strange....

 

Thanks in advance,

-psyber7

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Are you saying that you've never seen less than 30' accuracy? How many satellites are you receiving and do you see a WAAS signal - (Sat above 32)? Do you have D's displayed on the bars for the regular Sats?

 

I get 20'-30' inside my house! Yesterday, I was getting 27' under a heavy tree canopy. Routinely in an open area, I get 10'-12'.

 

Once you get within the circle of accuracy, it is not uncommon for the compass needle to rotate randomly. That is to be expected because the unit thinks you are at the destination.

 

Do you have trouble with automatic watches keeping time? Are you keeping the unit in a location near your upper body and not stuffed in a packet or a backpack?

 

What kind of accuracy do other folks with GPS's receive in your area?

 

Although I don't use one, I understand a good quality external antenna improves accuracy a little, but you're not in the ballpark of what you should be getting. Is there anything else we're missing here that I haven't mentioned?

 

Okay, here's the deal. I just walked outside and I was getting an avg. accuracy of 68 feet (receiving anywhere from 4 to 7 sat's, under cloud coverage) in which none of them are labeled higher than 27.

 

I came back indoors and I am now receiving an accuracy of 24 feet with six sat's locked on (at this very moment) in which the highest satellite is labeled # 26

 

Does this mean that I am not getting a WAAS signal? Furthermore, why would I get better accuracy indoors than outdoors? Strange....

 

Thanks in advance,

-psyber7

 

One of the main problems, perhaps the only one is that you're not receiving a WAAS signal. It will show up higher than # 32 on the Satellite page display. Make sure you have it "ON" and try again later, outside.

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Some times when I'm searching out a cache, it will tell me 20 feet in that direction then I take a step or two towards that direction and it switches direction and changes the distance to the waypoint.

 

This is common to all GPS units. Here's the work-around:

 

As you get close to the target, watch the coordinates, not the pointer. You may have to switch screens to see the coordinates, depending on how you have your unit set up. Just move around slowly until the coordinates match the target's figures. You will be very close!

 

-Paul-

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Tlhutch: I checked again today and the highest sat i'm locking on to is #30. I live 40 minutes inland from boston, I beleive I read that there are WAAS towers placed on both coasts? I triple checked that WAAS IS enabled. Any ideas, on why I can't get a WAAS (#32 or higher) sat?

 

PFF: thanks for the advice!

 

Thanks!

-psyber7

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the 3 meter accuracy is the idealistic position....not necessarily the position that it would calculate all the time

 

The WAAS specification requires it to provide a position accuracy of 7.6 meters or better (for both lateral and vertical measurements), at least 95% of the time. Actual performance measurements of system at specific locations have shown it typically provides better than 1.0 meters laterally and 1.5 meters vertically throughout most of the contiguous United States and large parts of Canada and Alaska.[2] With these results, WAAS is capable of achieving the required Category I precision approach accuracy of 16 m laterally and 4.0 m vertically.

 

http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System

 

 

http://upload.wikimedia.org/wikipedia/en/0...em_Overview.jpg

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CS: That did it! I turned it back to normal mode & it locked on to sat #51 with an accuracy of 21 ft. outdoors.

 

Thanks everyone!

-psyber7

 

I'm glad you solved the problem. That's an easy one to overlook. Allow it to sit for a bit and the accuracy should come down to less than 15' at least, in most locations....

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Some times when I'm searching out a cache, it will tell me 20 feet in that direction then I take a step or two towards that direction and it switches direction and changes the distance to the waypoint.

 

This is common to all GPS units. Here's the work-around:

 

As you get close to the target, watch the coordinates, not the pointer. You may have to switch screens to see the coordinates, depending on how you have your unit set up. Just move around slowly until the coordinates match the target's figures. You will be very close!

 

-Paul-

I always find it easier to view the map screen zoomed in, and forget the compass all together. Just walk until the arrow is on top of the cache box. Zoom in more and more as you get closer.

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Tlhutch: I checked again today and the highest sat i'm locking on to is #30. I live 40 minutes inland from boston, I beleive I read that there are WAAS towers placed on both coasts? I triple checked that WAAS IS enabled. Any ideas, on why I can't get a WAAS (#32 or higher) sat?

 

PFF: thanks for the advice!

 

Thanks!

-psyber7

 

What a big tower. The WAAS signals come from satellites in Geosynchronous/geostationary orbit 26,200 miles up.

Now we on the east coast, I too am only about 40 miles from Boston, are saddled by the loss of the eastern WAAS satellite which for the last 3 months has diluted our EPE capability.

 

http://forums.Groundspeak.com/GC/index.php...=175640&hl=

http://forums.Groundspeak.com/GC/index.php...=175670&hl=

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