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Garmin Oregon 450


EarLady
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I recently got a Garmin Oregon 450 and I LOVE it. I've been quite successful with it, but today I was out caching and I was zero for two. Both times I was dead on (within 1 foot) according to the Oregon, but there was no cache in sight. How accurate can I expect to get? If I am standing on ground zero according to the GPSr, about how many feet away could the actual cache be? I tried both the normal mode and WAAS mode with no difference.

 

Any help would help. Thanks!

EarLady

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Just remember, the GPS is taking you to the posted coords period, not to the cache. Like NordicMan said, you could be off 15’ on a good day and the hider could be off 15’ on a good day. That equals up to 30’ off on a good day. It also depends on the topography around you. In your area I’d expect caches to be within 40’-50’ of your GPS.

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How accurate can I expect to get?
You can do your own quickie "repeatability" experiment in your front yard. It won't tell you how close you'll get to someone other cacher's coordinates (no telling what they're using or how careful they have been), but at least you'll know how solid your own unit is.

 

On half a dozen different days and at different times of the day, park yourself and your 450 on the same known spot, preferably with a clear view of the sky, and especially to the south. You'll get all of your info from the satellite page (tap the bars at the bottom center of the screen).

 

Make sure WAAS is turned on (Setup / System / GPS / WAAS/EGNOS). Be sure to turn your unit on first and allow it to settle for a couple of minutes. Wait until you have a green bar for either satellite #48 or #51 and little "D"s at the bottom of your green bars for the other satellites.

 

Wait to be sure that the coordinates on the satellite page aren't wandering and let it sit for one minute. Take a reading at that spot and record it along with the "GPS Accuracy" that is displayed.

 

Once you have your 6 readings, it's some quick and dirty math (we'll use simple averages instead of anything more complicated - means vs. medians and mean deviations, and all that).

 

Find the average of the latitude readings. Find the average of the longitude readings. We'll call that "ground zero" for the moment.

 

For each 0.001 of difference in latitude between your "ground zero" and the other readings, you can figure that cost you about 6 feet in north/south error.

 

For each 0.001 of difference in longitude between your "ground zero" and the other readings, you can figure that cost you about 4 feet in east/west error.

 

Of course, 0.001 really means 6~11 feet of latitude, and 0.002 really means 12~17 feet, but let's ignore that for now.

 

Report back. I'll be curious to know how you did. Oh, and for each reading, remember to record what your GPS said the 'accuracy' was. The more times you do it (we'll work with 6 for now), the better idea you'll have of what is possible.

Edited by ecanderson
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How accurate can I expect to get?
You can do your own quickie "repeatability" experiment in your front yard.

 

Personally - I just do this using my water meter cover in the front yard. It's my personal 'benchmark' for testing any unit that I happen to have my hands on.

 

FWIW: I've found my Oregon 400t to be within 5 feet of the original coordinates at worst, and right on at best (original coords were averaged for 20 minutes, then had an additional sample of averaging added a week or two later).

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How accurate can I expect to get?
You can do your own quickie "repeatability" experiment in your front yard. It won't tell you how close you'll get to someone other cacher's coordinates (no telling what they're using or how careful they have been), but at least you'll know how solid your own unit is.

 

On half a dozen different days and at different times of the day, park yourself and your 450 on the same known spot, preferably with a clear view of the sky, and especially to the south. You'll get all of your info from the satellite page (tap the bars at the bottom center of the screen).

 

Make sure WAAS is turned on (Setup / System / GPS / WAAS/EGNOS). Be sure to turn your unit on first and allow it to settle for a couple of minutes. Wait until you have a green bar for either satellite #48 or #51 and little "D"s at the bottom of your green bars for the other satellites.

 

Wait to be sure that the coordinates on the satellite page aren't wandering and let it sit for one minute. Take a reading at that spot and record it along with the "GPS Accuracy" that is displayed.

 

Once you have your 6 readings, it's some quick and dirty math (we'll use simple averages instead of anything more complicated - means vs. medians and mean deviations, and all that).

 

Find the average of the latitude readings. Find the average of the longitude readings. We'll call that "ground zero" for the moment.

 

For each 0.001 of difference in latitude between your "ground zero" and the other readings, you can figure that cost you about 6 feet in north/south error.

 

For each 0.001 of difference in longitude between your "ground zero" and the other readings, you can figure that cost you about 4 feet in east/west error.

 

Of course, 0.001 really means 6~11 feet of latitude, and 0.002 really means 12~17 feet, but let's ignore that for now.

 

Report back. I'll be curious to know how you did. Oh, and for each reading, remember to record what your GPS said the 'accuracy' was. The more times you do it (we'll work with 6 for now), the better idea you'll have of what is possible.

Link to comment
How accurate can I expect to get?
You can do your own quickie "repeatability" experiment in your front yard. It won't tell you how close you'll get to someone other cacher's coordinates (no telling what they're using or how careful they have been), but at least you'll know how solid your own unit is.

 

On half a dozen different days and at different times of the day, park yourself and your 450 on the same known spot, preferably with a clear view of the sky, and especially to the south. You'll get all of your info from the satellite page (tap the bars at the bottom center of the screen).

 

Make sure WAAS is turned on (Setup / System / GPS / WAAS/EGNOS). Be sure to turn your unit on first and allow it to settle for a couple of minutes. Wait until you have a green bar for either satellite #48 or #51 and little "D"s at the bottom of your green bars for the other satellites.

 

Wait to be sure that the coordinates on the satellite page aren't wandering and let it sit for one minute. Take a reading at that spot and record it along with the "GPS Accuracy" that is displayed.

 

Once you have your 6 readings, it's some quick and dirty math (we'll use simple averages instead of anything more complicated - means vs. medians and mean deviations, and all that).

 

Find the average of the latitude readings. Find the average of the longitude readings. We'll call that "ground zero" for the moment.

 

For each 0.001 of difference in latitude between your "ground zero" and the other readings, you can figure that cost you about 6 feet in north/south error.

 

For each 0.001 of difference in longitude between your "ground zero" and the other readings, you can figure that cost you about 4 feet in east/west error.

 

Of course, 0.001 really means 6~11 feet of latitude, and 0.002 really means 12~17 feet, but let's ignore that for now.

 

Report back. I'll be curious to know how you did. Oh, and for each reading, remember to record what your GPS said the 'accuracy' was. The more times you do it (we'll work with 6 for now), the better idea you'll have of what is possible.

 

Just getting back to this forum. Thanks for the replies everyone. I'll try this and post results.

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I recently got a Garmin Oregon 450 and I LOVE it. I've been quite successful with it, but today I was out caching and I was zero for two. Both times I was dead on (within 1 foot) according to the Oregon, but there was no cache in sight. How accurate can I expect to get? If I am standing on ground zero according to the GPSr, about how many feet away could the actual cache be? I tried both the normal mode and WAAS mode with no difference.

 

Any help would help. Thanks!

EarLady

Another possibility not covered here is that the cache was in sight, but you didn't see it.

 

This is especially likely for micros. Some of them are EVIL - you can be looking straight at them from 4-5 feet away and not realize it.

 

As an example, I remember one cache that was hidden near a bathroom. There were a few plastic sewage ventilation pipes sticking from the ground near the bathroom, however one was slightly oddly placed. It turned out to be the cache. I would have stood right next to it and not realized it if I hadn't decided to read the hint.

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