Google Earth

[Root Canal]

Are Google Earth's GPS coordinates accurate? The reason I ask is I loaded 3 of them into my Humminbird while at the house. When I pulled them up on my screen, each location was about 1/4 mile off. Each one was different. One was off South west, one was off to the East, and the third was off North west.
If no one is having a similar problem, I guess my GPS is bad.
Thanks.

[Robalo]

The Datum used for GPS' is WGS-84 and Google Earth likely uses NAD 1983, so there is a difference between the different Datums. NAD 1927 on a State Plane Projected Systrem is about 100' off from WGS 84 and not sure what NAD 1983 is off from WGS 84, but likely about 100-200' or so. Different Datums cause variances and you need to adjust for the differences when loading from one Datum to another.

[Root Canal]

Thanks Robalo.
I contacted Derek from Breakwater Marine. He is going to see if he can figure out a method to help. He said you are correct.

[kenny]

The Datum used for GPS' is WGS-84 and Google Earth likely uses NAD 1983, so there is a difference between the different Datums. NAD 1927 on a State Plane Projected Systrem is about 100' off from WGS 84 and not sure what NAD 1983 is off from WGS 84, but likely about 100-200' or so. Different Datums cause variances and you need to adjust for the differences when loading from one Datum to another.

Damn Robalo, your sure smarter than you look!

[jig head]

I have manually entered coordinates into my gps (garmin 6##c) from both hot spot maps and google earth and both have been accurate. I know they are accurate because the coordinates are for shallow reefs and cuts and if 20 ft off i would have known it. For Google earth I did have to cahnge the gps format on Google Earth to Degrees, Decimal, Minutes to work properly for some reason.

[Robalo]

Jighead:

You were lucky!! I am guessing your GPS uses NAD 1983 or you were able to change Datums on your GPS-some allow for that or allow you to advise or they automatically see the different datum and change it or pick the correct datum. Mine doesn't and I was using the MMS Website as well as "OWL" (pay website for "Offshore Wells and Leases") locating old wellsites and also gives you pipeline taps and the MMS as well as Oil Biz generally use NAD 1927 as the datum and if not corrected to WGS 83, you are off by 100-200'-which doesn't matter as to existing wells/platforms but will as to P&Ad wells from the old days when the DOI didn't make oil companies do all the site clearance back in the 50s, 60s and early 70s so a lot of stuff was left on the bottom-a lot of those show up as "snags" on the NOAA Obstructions sites.

Yep Kenny-every now and then I can fool ya!!!

[Robalo]

BTW Root Canal-there are websites that convert datums. I just can't remember where they are-too old and too many beers thru the gullet.

[lurefisher]

I don't no about all the differences ,but prob. ten years back when Sneeky got his first hand held gps.He said ok Deano here's the deal we were headed out 2004 in chocolate they got green and red bouys marking ICW .Sneeky Pulls the boat over to a green bouy and marks {saves} the location and goes to the next one and so on.Well we turn around and go back to the first one marked and sneeky goes ok heres the deal IM going to put this coat{jacket} over my head and look down at the gps and drive .Your job is to not let me run into the bouys if it looks like i am.I said ok but why do you think your gunna hit them well they tell me deano that what you mark is a little off or something I said ok .Boy were they wrong ,he took off and i grab the wheel and Sneeky came out from under the coat we were going to hit the bouy,From that day on we trusted the gps.

[TroutDoc7]

Pulling

Any dentist should know when you "pull something up" the results often are different than what you anticipated. Just joking, one dentista to another.

[castaway300]

The Datum used for GPS' is WGS-84 and Google Earth likely uses NAD 1983, so there is a difference between the different Datums. NAD 1927 on a State Plane Projected Systrem is about 100' off from WGS 84 and not sure what NAD 1983 is off from WGS 84, but likely about 100-200' or so. Different Datums cause variances and you need to adjust for the differences when loading from one Datum to another.

say what, could somebody translate for me

[castaway300]

gps

If you have a eagle/lowrance unit you can buy a mapping program to run on a pc/laptop. I plug gps cord. from goggle earth into the program. create a file, load the file onto a memory card, plug the card into the gps, downlod. go fish.
i did try plugging cord. i got from goggle into my gps and like you i was way off. I guess the mapping program converts it or something.
hope this helps

[lurefisher]

If you have a eagle/lowrance unit you can buy a mapping program to run on a pc/laptop. I plug gps cord. from goggle earth into the program. create a file, load the file onto a memory card, plug the card into the gps, downlod. go fish.
i did try plugging cord. i got from goggle into my gps and like you i was way off. I guess the mapping program converts it or something.
hope this helps

I run the lowrance H2o C and like it a lot, im going to have to get the gps cord and program for the pc sounds good.

[castaway300]

mapcreate 7 is the latest one they have out.
castaway300

[Walker]

I often download tracks from my Garmin (WGS-84 coordinates) into Google Earth and they are dead on when I look at them. It may be that the downloaded track also contains info that tells Google Earth that the coordinates are WGS-84 referenced.

[Robalo]

Mapcreate and auto conversions take care of the datum differences. NAD stands for "North American Datum" and the number stands for the year. So NAD 27 is 1927 and NAD 83 is 1983 and if ya plug NAD 27 datum coordinates/lat lons into a NAD 1983 datum, you are off by 100-200 feet or so. I aint no geographer, so don't know why they chnage stuff. But think of the different cards/chips for you GPS-ya can't put a Garmin Chip in a Lowrance or Furano-they all made their own.file extension in their software so we can't trade cards between different mfg units-it kinda works like that with different datums. I think Lowrance uses a .usr type defined file, Google Earth uses a .kml type file-my genius engineer brother figured it all out and we loaded about 300 waypoints that were NAD 27 based and he was able to download and convert to .usr for the chip and then download into my gps. Wheww, too much datum for me.