[Proj] Google Earth Accuracy

[Richard Greenwood]

On Wed, Dec 17, 2008 at 8:24 AM, Landon Blake <lblake at ksninc.com> wrote:

> Richard wrote: "NAD83 is fixed to the North American plate."
>
> This can get complicated to. You have to factor in issues of local and
> regional movement. For example, where I live, regional subsidence can be
> a real problem. But I'm in California, and in California you start
> dealing with all types of ground movement, like that along the North
> American and Pacific plate boundary.

You might find http://www.ngs.noaa.gov/TOOLS/Htdp/Htdp.html interesting.

> One important thing to remember is that in most cases, people are
> worried not about absolute coordinates, but the spatial relationship
> between "things" on the Earth's surface. That's why plate tectonics
> usually isn't an issue in boundary surveys. :]

Where I'm getting burned is integrating geocentric datum data with
NAD83 datum data when the data provider and/or the software doesn't
know the difference.

-- 
Richard Greenwood
richard.greenwood at gmail.com
www.greenwoodmap.com