[time-nuts] question about Thunderbolt geo accuracy

[Chris Albertson]

On Thu, May 10, 2012 at 9:07 AM, Bob Camp <lists at rtty.us> wrote:
.
> Hi all,
> Hope this isn't too chat roomy, however, I have need of a survey precise
> geolocation type gps.  I was wondering if the precise timing abilities
> extend to its precision in position output?  I have a thunderbolt and
> one of those conical white aerials from china and would like to know if
> this combination will give me accurate height data.


It will give "pretty good" height data.  Within a few meters but you
have to know how to translate between different definitions of "sea
level" to make best use of the data.

If you live in the USA you can now download for free the USGS
topographic maps.   I'm pretty sure thy have full coverage of all of
the US.  THese will have 20 foot contour intervals and you can
interpolate to at least half that.   So for most normal purposes you
can find your elevation without a GPS.   Just look on the topo map.

Most of these maps where made with stereo camera pairs.  They get
relative elevation optically by matching the two images and then they
sent survey teams to ground check some points.


Chris Albertson
Redondo Beach, California