Garmin & Google Earth

[Capt Gary]

When I mark spots on Google Earth and then go there my Garmin 76CSx is way off. My son has done the same thing with his unit and we don't understand why.

I've been trying to go onto Google Earth and mark spots to hike and maybe hunt. When I visit the areas the readings from GE and the ones on my Garmin 76CSx are way off. Checked them with my sons Lowrance unit and his if off also.

What's up. Is GE off that far or are we doing something wrong?

We are new to the game and any help would be greatly appreciated

[crawil]

At certain points on the globe, Google Earth really is that far off.

[XC_Tracker]

Google Earth is way off - it's free - you get what you pay for.

[segler999]

It's Navtek that's off, but only for certain features. GE and many other mapping apps get their georeferencing data from Navtek.

 

The amount that's off varies, too.

 

In eastern Oregon mountains the entire map georeference is off to the east by about 75' or so. I am hiking on a very sharp ridge top, but my gps track shows me way down the east slope.

 

In western Washington, Forest Service roads to the north of Mt. Rainier are off to the east by about 250', but the GE images appear to be pretty close. I have done some recent hiking on logging roads that show up in GE. My gps tracks go right down the roads accrately, but the GE road overlays are off by that 250' feet too far to the east.

 

All these sources are working pretty hard to get their georeferences as accurate as they can. As they get inputs from data in the field, their mapping products will continuously get more accurate. It will take a while.

[+Latentk]

I have not had time to put adequete research into this but I am not entirely sure of Google Earth's map datum. Please do a wikipedia search for information concerning specific map datums. If you use one map and coordinates from one datum, and transfer either the map or the coordinates to another datum, you will be off by fairly large amounts. I am almost positive there is a likely descrepency between GE and your GPS'. You more often then not change map datums on your GPS to fit whatever datum GE is in! Hope that helps!!!!

[XC_Tracker]

When using Trimble or Lieca GPS units and importing waypoints into GE they will appear referenced correctly as referenced on the elliptoid, it is actually the imagery in the software that is not placed properly. The datum is usually not the problem, just what references the eye uses don't seem correct.

[gallet]

In my part of the world I have found that google earth, maps.google and my paper maps to be in perfect alignment. That's not to say it is correct everywhere.

 

[robertlipe]

What you're observing is most likely imagery misalignment. In some areas it's accurate to inches and in some rare cases can be off hundreds of feet.

 

The easiest way to prove it is to take a GPS track of your area while driving. Lay that track in Earth. Turn on the roads layer. Ideally, your GPS track, the road layer, and the aerial/satellite imagery will all agree within some reasonable amount.

 

If you see the road layer and the GPS track agree, but the imagery is offset by some constant amount in one direction, it's imagery misalignment and should be reported

 

http://groups.google.com/group/earth-data/...51da880c2f163f9

[+WaylessWood]

Google Earth also seems to have a problem when you drag the screen around. If I transfer a waypoint from my GPS the initial location looks pretty good. I zoom in some and then pan the screen. When doing this, the waypoint ends up in a different location. Since I knew the location of the waypoint in question and could clearly see the location in GE and the fact that GE showed the waypoint somewhere else, I would be suspicious of GE. Then again, it is free.

[robertlipe]

I've also moved hundreds of thousands, if not millions, of points from GPS to Earth in various OSes and versions. I've spent many hours panning, using combinations of keyboard and 3D Space Nav, and have never seen it move a PlaceMark when I didn't ask it to. I'd be very interested in hearing a reproducible test case for whatever problem you're describing, WaylessWood, and would get it into the right hands at Google to fix it if it's real and not just a misunderstanding of how things works.

 

I really don't get the couple of correlations here about "free" automatically equating with being not good. I've used terrible software that was expensive and great software that was free....

[+Brassine Family]

I'm still waiting for google earth to show my house that We started building 18months ago.

 

I'm also waiting for google earth to remove my truck that I haven't had for 3yrs from my parents' driveway!

[+user13371]

...initial location looks pretty good. I zoom in some and then pan the screen. When doing this, the waypoint ends up in a different location...

Do you have your waypoint clamped to ground, or with the GPS derived elevation?

 

A point not clamped to the ground will appear to move around when you pan the t in Google Earth. It will only appear on the correct spot if it's exactly centered on the screen.

 

If you're not sure, get info on the waypoint in Google Earth and click the Altitude tab.

Edited October 6, 2008 by lee_rimar

[+julianh]

Do you have your waypoint clamped to ground, or with the GPS derived elevation?

 

A point not clamped to the ground will appear to move around when you pan the t in Google Earth. It will only appear on the correct spot if it's exactly centered on the screen.

 

If you're not sure, get info on the waypoint in Google Earth and click the Altitude tab.

Yes, you need to be sure to lock your waypoints to the ground surface; otherwise, their apparent location can shift due to perspective effects as you pan around, if they are "floating" above or below the ground surface, and you have 3D terrain turned on.

 

Also, be aware that the actual location of any waypoint that you mark in Google Earth is actually the extreme tip of the "pin", NOT the centre of the "cross-hairs" in the waypoint marker icon. As you zoom in and out, as long as you have locked the waypoint to the ground surface, you should find the tip of the pin stays fixed, but the centre of the cross-hairs will seem to shift as the scale changes.