Can Goggle Earth's co-ords possibly be this accurate?
 17 years
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I'm trying to figure out what source of coordinates comes closest to the coordinates displayed on my GPSr. First attempt was with lat/long coordinates from Google Earth.
For one latitude measurement (and this was typical), my GPSr read 38.87925 deg at a spot that Google Earth said is at 38.879218 deg lat. The way I figure it, that's a 0.000082% variance btwn the two: (38.879218 - 38.87925)/38.87925 = 0.000082%
First of all, does that math make sense as a way to measure variance btwn Google Earth and my GPSr?
Second, does that mean that the variance btwn the two, as measured in feet at that latitude, is only about 12 ft? Here's the math I used, given that one degree of latitude is about 70 mi and one mi is 5280 ft: 0.000082% x 38.87925 x 70 x 5280 = 11.8 ft
TIA for any helpful comments.
You mean can your GPSr be this accurate?
Can Google Earth's Co-Ords possibly be this accurate?
I assumed that Google would put a lot of effort into calibrating each image, before loading it into the system.
0.000082% x 38.87925 x 70 x 5280 = 11.8 ft
I couldn't decide if the "% difference approach" made sense or not, but using the actual numbers gives the same answer.
Assuming your other numbers are correct - I'm too lazy to check
38.879250 - 38.879218 = 0.000032
0.000032 x 70 x 5280 = 11.8
So if your GPSr was claiming an accuracy of +/- 12' at the time, that would be right. What puzzles me, is why the GPSr's give coordinates to so many places of decimals, when they have such a large degree of error (relatively speaking!).
Shouldn't the GPSr have said 38.8793 and left it at that?
------------------------ Phil Hornby, Stockport, England ---------------------- http://GeePeeEx.com - Garmin POI Creation made easy »
Accuracy of Google Earth Coordinates
Hmm. My question does read as if I assume that my $300 GPSr is the accurate instrument, and that I'm judging the accuracy of the vaunted Google Earth by how well it agrees with my GPSr.
Actually, I wasn't thinking of it that way.
If my GPSr agrees with _any_ provider's coordinates, that would mean I have a good working combination for my own use. But I was thinking beyond that, to the day when I start offering POI files for use by others: Would my POI coordinates be accurate enough for them?
If my GPSr is in sync with Google Earth, that's good. If Google Earth gives accurate coordinates, that's much better: I can create accurate POI files for others, with confidence.
Thanks very much for confirming my math reasoning. When something seems too good to be true, I usually suspect that it is.
Garmin DriveSmart 55 & Traffic | Garmin eTrex "yellow"
Google Earth
google earth is very accurate in its coordinates. i have uploaded many boat ramps to the us boat ramp file using google earth. and some of them i have reverified with my gps driving to the locations. so i would say that it is very accurate. really though your gps is only accurate up to 10 feet anyway because of government regulations.
Garmin Nuvi 360, Etrex Legend, Oregon 200; Lowrance 520c. "We herd sheep, we drive cattle, we lead people. Lead me, follow me, or get out of my way." -General George S. Patton
I Don't Know About GE????
I've had mixed results with Google Earth. Sometimes the coordinates are spot-right-on. Other times they've been off by 12 - 15 miles. I have no idea why and double checked the bad coords at least twice. Same result each time.
"Wherever You Go, There You Are!" (Doctor Who)
Preferred meathods
New to creating POIs, I am also trying to learn the language and the "best" way to locate coords. Google Earth is a quick way for me to locate points at my desk - while reading the coordinates from my GPSr is another way. I'm curious if a KML file created in GE is a good tool for transferring coordinates? How are new traffic enforcement camera locations typically submitted? Anybody?
Nüvi 760 since Xmas.
How are new traffic enforcement camera....
...locations typically submitted?
http://www.poi-factory.us/node/455
*Keith* MacBook Pro *wifi iPad(2012) w/BadElf GPS & iPhone6 + Navigon*
Both could be right!
Both your TT and GE could be correct. The issues come into the degrees of accuracy. Your TT is measuring to the nearest 5 decimal places and GE to 6.
I would equate it to measuring a wall, one person using inches and the other going down to quarter inches. Both would be right, one is just more right.
submit or report
...locations typically submitted?
http://www.poi-factory.us/node/455
How are enforcement cameras reported?
Nüvi 760 since Xmas.