[time-nuts] OT [GPS Survey grade RX]

[Jim Lux]

When you start getting to less than a meter.. For absolute, you need to start worrying about stuff like solid earth tides, plate movement, a whole host of things are all contributors in that 10-100 cm range.   

For relative work( most surveying) the effects are small over a distance of tens of I'm, so 1ppm sorts of accuracy is possible.

For precision attitude, e.g gun laying, differential carrier phase works pretty well, but consider what sort of phase measurement performance is needed over a say one meter baseline with 20cm wavelength.

On Dec 5, 2010, at 11:31 AM, Brooke Clarke <brooke at pacific.net> wrote:

> Hi Brian:
> 
> A friend has an Android cell phone with built in GPS.  It has a resolution of 0.0001 arc seconds as does the GPS I just got for my camera:
> http://www.prc68.com/I/Nikon.shtml#GPS
> 
> I think it's a common feature of the newest SiRF chip set.  What's not know is how accurate they are.  My friend thinks the resolution is really accuracy, but I'm skeptical about that.
> 
> The last few generations of military GPS receivers have an application called "Gun Laying" (aka. North Finding) that works by doing carrier phase measurements to determine the distance and bearing between any two points where you can get from one to the other in under 3 minutes.
> http://www.prc68.com/I/DAGR.shtml#AzD
> This can be used to make a relative survey.  To get an absolute survey typically requires post processing or use of differential corrections (LF beacons or WAAS).
> 
> Have Fun,
> 
> Brooke Clarke
> http://www.PRC68.com
> 
> 
> wa1zms at att.net wrote:
>> I wish to survey some of my land here in the US. What used GPS receivers out there might be good candidates?
>> 
>> I really don't want to haul a Z3801A out in the woods and run a self-survey unless the cost is too high. :-)
>> 
>> 
>> -Brian, WA1ZMS
>> 
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