[time-nuts] question about Thunderbolt geo accuracy
Jim Lux
jimlux at earthlink.net
Thu May 10 19:50:44 UTC 2012
On 5/10/12 9:18 AM, Chris Albertson wrote:
> 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.
>
>
And updated the elevation data with radar measurements from SRTM, as well.
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