explorist 310??

[robgwv]

When i transfer my gps way points to google earth there off by about 1/4 mile? Any ideas why

 

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[boogeyman]

Are you using the same map datum on both the GPs & GE? That sounds like the problem.

 

[Clay Diggins]

It could partially be due to mismatching datum but I doubt it. Your GPS is more than likely set from the factory as WGS84 Datum. That essentially the same as NAD83 since you are in the United States. Google Earth doesn't follow normal datum guidelines but basically they use WGS 84.

Your GPS unit could be set to NAD 27 but that's not going to put you anywhere near 1/4 mile off. The maximum error would be 600 foot (1/10 mile) and it would actually be a lot less in West Virginia (60 foot).

More than likely what you are experiencing is a combination of errors that add up to a big difference. The biggest error is assuming Google Earth has a consistent accuracy. Even though it popularly known as a mapping tool, knowledgeable map makers will tell you otherwise. Even Google doesn't want you relying on their mapping.

From Google:

Google makes no claims as to the accuracy of the coordinates in Google Earth. These are provided for entertainment only and should not be used for any navigational or other purpose requiring any accuracy whatsoever.

Our imagery varies from sub-meter resolution in major cities to 15 meter resolution for most of the earth's surface, with a global base resolution of 1KM. Since our database is constantly being updated, we cannot state a specific resolution for any geographic region.

Google acquires imagery from many different sources with many different file formats, projections and spectral characteristics. All imagery sources are fused into a single global database with a proprietary format that has been developed for the specific purpose of streaming to our client software.

What that means in mapspeak is the accuracy could be anywhere from 3 foot to 1 1/4 miles.

Sometimes Google Earth can be good and sometimes you would be much better off with the Pirates of the Caribbean map from Disney. That's the nature of the Google Earth experience. Try to think of it as "entertaining".

There are some things you can do to make your Google Earth entertainment less frustrating.:

1. Try turning off the "terrain" feature, it pretty much destroys any accuracy there was in Google Earth. False 3D is fun but it's not good for serious accurate mapping.

2. Make sure your GPS is set to WGS 84. Google Earth doesn't automatically reproject your GPS datum like real mapping programs.

3. Don't believe the distance measure or scales in Google Earth. They are not very good entertainment.

4. When you record a waypoint with your GPS set it down with a good clear view of the sky and let it settle for at least 4 minutes before marking your waypoint.

5. Understand the limits of your tools. GPS is only reliably accurate within 30 foot. Your GPS could be more accurate in many circumstances but if you are in the northern US, you have your GPS in a pocket or a backpack, the sky is overcast and you are under tree cover you may not be getting any location information at all. If you are recording tracks expect them to wander over a large area (miles) in those circumstances.

Hope that helps.

 

[boogeyman]

Pulled mine out to use today. Forgot to mention if you're using the Vantagepoint program you should check the settings there too. Sorry I didn't think of it sooner. Real pain going from the old TOPO! pgms to Vantagepoint. Got the TOPO! bundle for $70 and I think I like my old 315 better. Google up GPSSWAY it's free and will convert your wpts to most any other format! Excellent pgm for a freebie!!!!!!

BTW - Their type talking customer service is terrible! Plan on spending 2 hours or more and getting no useful answers.