[BC] GPS

[Cowboy]

On Thursday 05 February 2009 10:31 pm, Larry Bloomfield wrote:
>  Well not so fast there Cowboy  :-)    You can get on line very easy. 

 Yes, and no.
 I've personally driven radials where no cell phone works, except satellite.
 Even so, a laptop with any reasonably accurate mapping package can
 connect to a consumer grade GPS and work more than adequately.
 For both cost and function, this will be VERY hard to beat.

>  Traveling the country, as I've been known to do, I refuse to pay some of 
>  the hotels where I stay $10 plus a day for internet access. Not all the 
>  hotels have wifi and not all offer free eithernet, so I have a little 
>  USB stick with Verizon Wireless and where ever I have cellphone service, 
>  I have internet service.

 Yes, well....
 Friends don't let friends have anything to do with verizon.
 I can not, will not, recommend verizon to any one for any thing.
 They slither a little to low for me.

>  BTW: will I get to see you again this year at NAB or on my Road Show?  
>  Looking forward to either or both. Buy ya a cop of java.   

 NAB, yes. It remains to be determined at which hotel, but I'm otherwise
 covered. ( got a plane ticket "in stock" already )

On Thursday 05 February 2009 11:29 pm, Alan Alsobrook wrote:

>  If you need to get a bit better accuracy on your bearing display (as 
>  long as I have the dead on target route line, I really don't need to) 

 You're catching on.
 The more accurately the original bearing is plotted, the less dependent
 one is on the resolution of the field unit.
 Once you have a true accurate bearing plotted on mapping software,
 and the GPS shows you where you are, you are no longer dependent
 on the GPS resolution for anything, no matter how good it is, or isn't.

On Thursday 05 February 2009 11:46 pm, Mike McCarthy wrote:
>  Precisely...  And at 10 miles, the mil is something less than 40 
>  ft.  Pretty darn tight.

 Not arguing that.
 It becomes an issue of measuring with a micrometer, marking the
 radial with spray-paint, and navigating with an ax.

>  HOWEVER, keep in mind there is a jitter factor on some RX's.  Remain 
>  stationary.and you will see the coordinates move about +/- 1 second in all 
>  directions.  So when you make things too tight,  you will see some jitter 
>  on the actual line.

 Nice to be within that error, don't you think ?
 That error will exist regardless, but rather than have it merely add to other
 error, and compounding, wouldn't it be nice if that's the ONLY error ?

 As mentioned in a previous, the first give-away on this is usually seen
 as changes in elevation when one is stationary.
 It's not due to any error within the unit, but due to timing changes as
 the satellite signal suffers bending and doppler effects propagating
 through the atmosphere.

 Unless, of course, you pay in excess of $4K and buy a Trimble surveyor
 grade GPS, which can resolve propagation errors as the satellite signal
 flutters, thus eliminating jitter.
 ( That unit can resolve well within one centimeter once calibrated against
 a local monument. ) 

 Even the consumer grade units, if allowed to determine its location, and
 all of its output recorded, can be used to get a very precise rendition of
 where it is. Average the jitter over enough time, and you'll get an area
 which you can be certain you are within. The longer ( and the more
 data points ) the average, the smaller the sphere where it says you are.
 Of course, none of us is going to take a day at each point to wash out
 jitter on any unit.

On Friday 06 February 2009 12:09 am, Jason R. wrote:
>  If I'm right Cowboy you can download a database from Google to make their
>  stuff usable off-line... 

 "Last I checked" which was admittedly a while ago.

 I'm not saying the mapping software that *I* use is necessarily the best
 for you, but works for me. That's partly why I try and make my plots as
 transferable as I can. In keeping with Unix tradition, Delorme text files,
 because in the worst case, you can manually transcribe them into anything.

 Last time we worked together, Folkert was using Street Atlas, Sadler likes
 Garmin. Burt has mentioned Delorme Topo-quads a few times.
 I don't particularly care, since none of these are gospel, and all are usable,
 when used correctly. Personally, I find the Delorme topo-quads every bit
 as good as paper USGS topo-quads, but much easier to navigate and plot
 when combined with any GPS and Delorme on a laptop.

 I plot Garmin and Delorme. ( and Linux gpsman as a consequence of the math )
 These two are quite popular among those of us who do or have done field proofs.

 Magellan is the other popular unit, though I don't have one, so I don't have
 an example of their file format.
 ( though I may acquire one, as the one I saw would plot the bearing 
 between to of my distance references, and tell you how far off of the
 bearing it currently is, and in which direction. Very useful on walk-ins
 with 1/10 or 2/10 distance reference points )

 The Trimble I worked with doesn't do mapping. No surprise there, being
 a professional grade unit, it doesn't have consumer "features" as it's intended
 to do one thing, and do it very, very well. Tell you where it is. Period.
 ( though it will do NMEA into mapping software via serial port )

 If you want a particular file format, send me the request and a sample of
 that file format along with the check, and I'll see what I can do. 
 Note that most windows stuff uses highly proprietary binary formats
 that are just too difficult to re-create without source code, but I'll see.

-- 
Cowboy