CSx & WAAS

[+DRMOO]

How can I tell whether CSx unit is actually benefitting from WAAS? Satellite screen seems to show the "Ds" on all but one bar. I'm in S Ontario. I seem to get same accuracy whether WAAS is "enabled" or "disabled".

[Live2Crawl]

I heard that WAAS only works in usa, doesnt it??

[+ICHTHYS]

WAAS can work throughout most areas of North America. But the further north or south of the US you get the less likely WAAS will work.

Edited January 24, 2007 by ICHTHYS

[planewood]

You will get the same reported EPE with, or without, WAAS. But, on average, the coordinates reported will be closer to the actual lat/lon when using WAAS.

 

Find a surveyed bench mark or triangluation station and try it a few dozen times on different days and different times of the day. Try it when the DOP is low (good) and high (not good).

 

Download the Trimble Planning software (free) to see the DOP charts.

[+NightPilot]

The satellites used for WAAS corrections are regular communications satellites in geosynchronous orbits over the equator, with the antennas aimed at the US. The corrections sent to them are only valid for US locations. Yes, it's possible to receive the satellites outside the US, but the correction information may not be valid. One thing to remember, though, is that much of the populated area of Canada is actually south of part of the United States, so yes, it's possible to get WAAS corrections from Canada. However, the further north you go in the US, the harder it is to see the satellites over the equator.

[planewood]

Canada right now does not have many control stations from which to build the correction grid. But, they're working on it.

[+EraSeek]

Here is the WAAS service area for full corrections:

http://www.nstb.tc.faa.gov/vpl.html

[+Red90]

You will get the same reported EPE with, or without, WAAS.

 

Ummm, not in my experience.

 

1.7 to 3.5 meters with WAAS in a reasonbly open area. 3.5 to 5 without. You need to hold a WAAS satellite locked for a few minutes for the corrections to take effect.

 

This coverage map is more important to us, the other link is for vertical accuracy.

Edited January 24, 2007 by Red90

[+DRMOO]

DRMOO thanks those above for their help. The WAAS profile maps show my area of operation is in excellent location to exploit WAAS. Got to find a nearby survey marker/point in an open area and do a with/without over a few days. Thanks for suggestion

[+EraSeek]

 

This coverage map is more important to us, the other link is for vertical accuracy.

 

Actually, no. My link is better to the actual area for this reason: The link you used does not include ionospheric corrections. "Non-Precision Approach (NPA) Navigation Mode. The Non-Precision Approach navigation mode refers to the navigation solution operating with a minimum of four satellites with fast and long term WAAS corrections (no WAAS ionospheric corrections) available."

 

The verticle protection level display does. You can get WAAS corrections well outside of north America that does not include ionospheric corrections (which amount to about half of the GPS errors), but these are sat postion and timing errors due to relativity. Most Garmins will not use WAAS unless it is within the grid which includes ionospheric corrections. My link shows that area in real time.

[planewood]

 

Ummm, not in my experience.

 

1.7 to 3.5 meters with WAAS in a reasonbly open area. 3.5 to 5 without. You need to hold a WAAS satellite locked for a few minutes for the corrections to take effect.

 

This coverage map is more important to us, the other link is for vertical accuracy.

 

You know, my testing on that was done with software that was 2 or 3 releases back. Maybe I should test it again.

[+EraSeek]

You know red90, looking at your gallery it looks like you have a 60cs or 60c. The 60cX that I have with the sirf chip acts differently than my old Map76. With the Map76 the EPE (accuracy reading) reacted in relation to whether I had WAAS on or off. With it off I would be at a 15' reading. With it on I might have a 6' reading. The 60CX does not do well in this area. With WAAS on or off the reading stays about the same. Bummer. It is a programmed reading anyway and does not accuratly reflect "accuracy". Testing on benchmarks, the unit does much better with WAAS on, but the accuracy reading does not show it. I'm thinking the 60c does better than the 60cx in this regard.

[+pdxmarathonman]

You know red90, looking at your gallery it looks like you have a 60cs or 60c. The 60cX that I have with the sirf chip acts differently than my old Map76. With the Map76 the EPE (accuracy reading) reacted in relation to whether I had WAAS on or off. With it off I would be at a 15' reading. With it on I might have a 6' reading. The 60CX does not do well in this area. With WAAS on or off the reading stays about the same. Bummer. It is a programmed reading anyway and does not accuratly reflect "accuracy". Testing on benchmarks, the unit does much better with WAAS on, but the accuracy reading does not show it. I'm thinking the 60c does better than the 60cx in this regard.

Just to make sure I am clear on what you're saying when comparing the 60cx and 60c:

The coordinates are more accurate on the 60cx when getting WAAS

The 60c is more truthful in reporting its accuracy with WAAS (with the 60cx being pessimistic)

[+Red90]

You know, my testing on that was done with software that was 2 or 3 releases back. Maybe I should test it again.

 

I think the WAAS almanacs for the new satellites got loaded in GPS Firmware 2.60

 

You know red90, looking at your gallery it looks like you have a 60cs or 60c.

 

I have a 60Cx. I always have the "GPS Accuracy" displayed on the map and navigation screens. I record waypoints quite often and the figures quoted match my experience. Before and after recording coordinates, I alway check to see if WAAS is active.

 

The 60CX does not do well in this area. With WAAS on or off the reading stays about the same. Bummer. It is a programmed reading anyway and does not accuratly reflect "accuracy". Testing on benchmarks, the unit does much better with WAAS on, but the accuracy reading does not show it. I'm thinking the 60c does better than the 60cx in this regard.

 

This in not my experience. I have tested on many benchmarks. IME, the actual error was always less than that reported. This plus over a 1000 geocache find leaves me confident that the reported accuracy is a good and accurate figure of probably 90% confidence level.

 

As stated, the reported accuracy value drops after WAAS is in effect. With the older "Garmin" receivers , the velue was almost exactly half of without WAAS. With the 60Cx, it varies from 50 to 75% based on my testing.

Edited January 25, 2007 by Red90

[scheister]

Just a quick exert from something I read in my owners’ manual regarding enabling WAAS that may shed some light on this discussion; please read below from the 76Csx manual.

 

"...For this reason, when you enable WAAS on your Garmin GPS receiver, the receiver automatically uses the method that achieves the best accuracy."

[+EraSeek]

To be clearer, Both the 60c and the newer 60cx will benefit about the same from using WAAS. WAAS increases accuracy and stabilty of position by eliminating (reducing) error.

 

The EPE or Accuracy Reading which is displayed on the GPS screen is a programed guesstimate of how your GPS is doing. It is not the true accuracy of the unit's postion. At any rate, my experience is that with my Map76 this worked well and was usful. With my 60cx, haveing WAAS on or off does not seem to influence this reading. None the less, with testing, I know that WAAS is really improving my position even though it is not reflected on this displayed number.