I want to put some of my GPS marks into google earth, but when I enter them they are way off. I am assuming the datum google earth uses and my GPS datum(WGS 84 or GDA 94) is different.
Can I get some tips on how to do it correctly.
Google earth & my GPS marks
I want to put some of my GPS marks into google earth, but when I enter them they are way off. I am assuming the datum google earth uses and my GPS datum(WGS 84 or GDA 94) is different.
Can I get some tips on how to do it correctly.
Maturity is not when we start speaking BIG things,it is when we start understanding small things
http://earth.google.com/userguide/v4/ug_importdata.html
It says Google earth is using WGS84, I have put a few spots in offshore and they look the same to me on my Eagle GPS. I looked at a few other comments on there forums mate and there were others that were a few hundred metres out to the south of positions.
Good luck with it
.........................'THE FLATHEAD ASSASIN'........................
Up the top left hand side of googleOriginally Posted by tropicrows
click on
Tools,
Options,
Under 3D View check Degrees,Decimal Minutes
Regards Frank
Thanks Frank
Maturity is not when we start speaking BIG things,it is when we start understanding small things
The coords of my front door on Google Earth match perfectly with those on my little Etrex. Lots of info on this page http://www.gpsvisualizer.com/
remember that google earth is not a navigation tool, it is a medium for displaying aerial photographs.....as such it is rougly registered to a map grid.
all the aerial phoptos are stitched to gether as best as possible ( seriously clever realy) but many of the parts of the image will not be from directly above.
As well as the complications with datum... I wonder what scheme thy use to account for the irregularities of the earth and the pats of satelites.
I know my place seems to be dipicted from a southeasterly aspect... judged from the effects of tree cover.
you may be lucky to find accurate sections but others may be quite a bit off....yeh this has been raised before.
cheers
Its the details, those little details, that make the difference.
I have an application on my mobile phone for using the GPS receiver it has on the golf course. The application web server enables you to look at your marks (front middle and back of each green) on an overlay of Google Earth images. For my home course Google Earth is out by about 10 metres to the SE. This seems to be a fairly common error level, but it is not standard, it will vary for each image overlay, and for the reasons Oldboot mentioned. Would expect the errors would be no more than 10 to 20 metres in the normal course though.
The digital imagery on google earth is a mozaic from a variety of sources and resolutions. As a result, spatial accuracy is quite variable and depends on the source which can be satellite through to high resolution aerial photography, and the degree of image rectification. You will tend to find that the highest accuracy will be in the built up city and urban areas.
Most of the imagery on GE has already been previously commisioned and has undergone image rectification which alligns and drapes the image over a DEM or digital elevation model. The more DEM points there are to register the image to the greater the spatial accuracy.
Some places have a better DEMs than others.
Cheers
Since it was designed as a land based system do marine DEM points exist or is that why I find it more innaccurate on the water sections along the coast. It can make some points seem quite close to teh coast when I know they are distant.?
What you are saying is pretty right. There are few ground points to register to on water apart from islands or marine structures that may be part of the image. The coordinates that are seen on google earth refer to the grid that underlays the digital imagery. The imagery is laid over top and known points on the image are registered/pinned to the corresponding known points on the grid/map (that's an over simplification and I apologize to any surveyors/spatial scientists reading). If there are few ground points used around the coast then images can be displaced in these areas and waypoints will appear to be "out" distance wise relative to the coast.
It is also important to ensure that the same datum is used on your gps as the map you are plotting points on to. For example if you plot AGD 66 coordinates on a GDA94/WSG84 map they will be about 200 metres out in a NW direction. Also make sure you are using the same coordinate format ie Deg Min Sec vs Degrees decimal. FOR EXAMPLE 147 deg 35' 35" = 147.5932 deg which can be a trap as I have seen some people interpet 147.5932 deg as 147 deg 59' 32" or vice versa.
Cheers
"For example if you plot AGD 66 coordinates on a GDA94/WSG84 map they will be about 200 metres out in a NW direction."
1. That should read in a SW direction
Yep sorry about that. I was thinking about the the movement of objects in AGD66 projection when they are converted to GDA94 - they are moved NE.
Cheers
Last edited by black runner; 24-07-2009 at 09:43 PM. Reason: Changed NW to NE as pointed out by SatNav
"Yep sorry about that. I was thinking about the the movement of objects in AGD66 projection when they are converted to GDA94 - they are moved NW."
1. No they move in a nominal NE'ly direction.
Yep I'll give up now - almost run out of compass points. SATNAV is correct, the displacement is NE. Reciprocals clearly aren't my strong point. My typo and corrected. Anyone need a navigator
???
cheers
Post 12 and Post 13 don't have Black runner quoted as saying the same things.
Post 12 by black runner- "Yep sorry about that. I was thinking about the the movement of objects in AGD66 projection when they are converted to GDA94 - they are moved NE."
Post 13 by SatNav - "Yep sorry about that. I was thinking about the the movement of objects in AGD66 projection when they are converted to GDA94 - they are moved NW."
1. No they move in a nominal NE'ly direction.
Redrocks.
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