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Coordinates on GPS different from Google Maps?
Von
Hello,

I try to put specific coordinates on a GPS, and the point that appears on the map of the GPS is different from the one on Google maps.

Basically the point shown on the GPS is not totally different place than on google maps

How is that possible?

Thank you in advance.
tcassidy
There is more than one way to express latitude and longitude numbers such as decimal degrees or degrees decimal minutes. Make sure you are using the same method for both systems. If you need to convert from one to the other, there are internet sites that can assist you such as

GPS Latitude and Longitude Converter

Terry
Ken in Regina
Hello Von,

There are many things that can be causing this.

1. Your GPS is a consumer device. It is only accurate to within a few meters at the very best. And that depends on having a very good signal. Your GPS may have a screen that tells you what it thinks the accuracy of the current reading is. That is useful information but it is also only an estimate and does not -- can not -- tell you which direction it is inaccurate.

.. 1a. You can improve this by standing in one place for at least a couple of minutes to let the reading stabilize before recording the coordinates. If your device has an "averaging" feature, use it for a minimum of thirty seconds, preferably more, whenever recording a location.

For more information on GPS "accuracy" you can read this thread:

http://www.laptopgpsworld.com/777-what-gps-accuracy-anyway

2. It is necessary to make sure your GPS device and Google Maps/Earth are using the same "datum" (look for "geodetic datum" with your search engine). The simplest is to make sure your GPS device is set to WGS84 (there is usually a place in the Settings on your device to do this). I'm pretty sure WGS84 is the datum used by Google Maps. Using different datums on the two displays will result in huge differences in where the same set of coordinates is displayed on the maps.

3. The calibration of Google Maps/Google Earth is not always correct. You can see this on the maps if you have set the view to the combined road map and aerial view. In many places you will see the roads from the road map do not lay exactly on top of the roads in the aerial view. I have seen examples where the calibration is out by as much as 1/2 mile. Yes, that means the road from the road map was laying over the aerial map view 1/2 mile from where the same road was displayed in the aerial view.

4. You did not say which Google Maps view you are comparing with the maps on your GPS device.When you combine the inaccuracy of your consumer GPS device (point #1) and the inaccuracy of Google Maps calibration (point #3) you will find that the opportunity for accumulated error can be very large.

5. Similar to point #3, the calibration of the maps in your GPS device probably is not perfect, either. If the calibration error of the maps in your device is in the opposite direction of the calibration error in Google Maps you can see the opportunity for another large error in what you see displayed on your device maps versus Google Maps even if the calibration error in each is small.

There are other considerations but those are the major ones to be aware of.

...ken...
Von
Thank you very much Terry and Ken, This is really helpful.

I have to let the GPS settle in for a while as you explained and I was already adding waypoints of spots in another country I want to go.

I have just tried the converter and I noticed that when I put the calculated result of coordinates I put on Google Earth/Maps, the spot shown in the GPS seems to be right one.

It looks like I have to convert each coordinates I put on Google to get the right spot on the GPS.

I had no idea I need to make a conversion from Google Earth to GPS, is that right?

Thnak you again.
tcassidy
The coordinate system used by a GPS - assuming you mean a handheld or PND - can be changed. Decide on a system that both the GPS and GE can agree on and you won't have to convert it.

Terry
Ken in Regina
Von, you haven't said what device you have. You should be able to set its coordinate entry/display configuration to the one that matches Google Maps/Earth.

On a Garmin device, like the Nuvi models, you might try something like:

- poke the Tool icon (little wrench)
- poke "Settings"
- poke "System"
- poke "Location Format"

- select the format that matches what you are having to enter in Google Maps/Earth.

...ken...
Von
Thank you.

I have a Magellan Explorist 510.

Basically, if I put a coordinate like 4522'06 N on GE, it is going to give me 45.3683333333. And yet I took the coordinates from a book that says the coordinate is definitely 4522'06 N
' I let the second coord besides for the example)

So basically to have something similar to what GE shows, on the GPS I have to put 45.3683333333, because putting 4522'06 N gives me something different on the GPS.
tcassidy
But one of those is in degree-minutes-seconds format and the other is decimal degrees. Try changing the Explorist coordinate system.

http://support.magellangps.com/support/assets/manuals/112-0012-001_A.pdf Check page 41 for Settings - Navigation.

Terry
Von
Thank you both of you Terry and Ken > problem solved.
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