[time-nuts] question about Thunderbolt geo accuracy

mike cook michael.cook at sfr.fr
Thu May 10 21:14:19 UTC 2012


Le 10/05/2012 21:50, Jim Lux a écrit :
> 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.

I found an online WGS84-MSL converter at:
<http://earth-info.nga.mil/GandG/wgs84/gravitymod/wgs84_180/intptW.htm>
however for my location this gives the geoid height at 51,89m wrt MSL 
and if I apply that to my Z3801A reported height it make the difference 
with my TBolt even greater.  I had read elsewhere , though I can't find 
the reference, that the difference at my latitude is more like 30m which 
would make more sense.

Can someone with a Z3801A  check the result for their location?

>>
>> 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.
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>



More information about the time-nuts mailing list