Vertical datum in Google Earth

I don't know this for sure, but ....

This is EXACTLY why many FIRM's are so screwed up...

I guess +/- 4 feet is okay when you're way up in the air at 300+ feet.

But being only about 6 feet above sea level in most spots, that 4' error is pretty major!

andy

James,

That was exactly my first thought as well.. Totally ridiculous. You're fired. end of problem.

> James,
>
> That was exactly my first thought as well.. Totally ridiculous. You're fired. end of problem.

It all pays the same. I billed them four hours for a bunch of nonsense they created over this. I should really think about adding a 40% aggravation stipend to my fee and if they can no longer afford me, end of problem.

good for you!

I get the calls from people that see the parcel lines on the county GIS and think their neighbor's garage is on their lot! grrr..

If any of you are using Google Earth elevations for jobs, like the song says," its just a matter time".
They are no better than the 7.5 minute USGS topo maps.

This is a bit off topic, but the Mat Su Borough has Lidar and imagery available through their website or available through the GINA website for most of the core areas of the Borough (excepting the Talkeetna Mountains area). This is good info to use for sanity check.

As far as GE vertical datum, this is what I found on the web:

"The vertical component (altitude) is measured from the vertical datum, which is the WGS84 EGM96 Geoid."

Good luck with the PIA clients. Have a good weekend.
Steve

> If any of you are using Google Earth elevations for jobs, like the song says," its just a matter time".
> They are no better than the 7.5 minute USGS topo maps.

Amen. This is the first time I've ever heard of anyone even mention "google earth elevations".... just does not compute.

Thanks Steve. I've been using the 1/2' resolution stuff in the core areas since last winter to augment some of my mapping projects. Really good stuff. I'm hoping to get some time this winter to play with the LIDAR data to see what I can do with it.

I'm sort of kicking myself for getting dragged into this whole GE elevation business, but I always try and give folks the benefit of the doubt and if I blew something, I'll man up, make it right and learn from it. I don't want to be an arrogant SOB, but sometimes ....

I like what Ron White said, 'You just can't fix stupid."

This is a great chance to be humble and educate a client. Try clicking on a rooftop on GE, then click on the ground 5 feet away.

Or, have them go to mapserver.mytopo.com/ and compare elevations to GE.

Help open their eyes.

fema_nfhl_v3.0.kmz
stay_dry_v3.0.kmz
if it floods there, search for and start google earth with either of these kmz files and it can demonstrate some level of comparison using fema cross sections.
my front yard is lower than ge says by 6'. my flood hazard property nearby is within a foot. either is probably just a coincidence.

if you do elevation certs they are a must have module for your toolkit

I tested it a few years ago. For a top phone where two ravines come together. I had noticed how close google was to a few control points I had for elevations and lat long. So I picked lat longs and elev for my project put them into my TGO file to generate coordinates and compaired the resulting topo to the field generated one. Not good!!!!! Up to 7-8 feet of difference but it wasn't just a shift, it was all over the place