[time-nuts] Computing GPS Distance Error in Time

[Bob Stewart]

Hi Chris,

This has to do with my GPSDO project.  I hadn't 
realized just how critical it was to have an antenna that is free of 
multi-path.  I've made several posts about my GPS marching around the 
neighborhood.  I finally put the antenna up in the attic at the peak of 
the roof and now the thing just marches around a small section of the 
house.  I still don't quite trust it, so I was just looking for 
something canned that would do the plotting for me.  I now have 
foxtrotgps running in its own section of the workspace, and it's no 
longer wiping the screen.  So, I think I'm good.

BTW, with fixing
 the antenna and switching to an Adafruit Breakout GPS, it looks like 
I've finally achieved phase lock using Bert's (VE2ZAZ) FLL board.  Now 
it's just a matter of cleaning up the code and
 making it more robust.  What an educational project this has been!

Bob - AE6RV




>________________________________
> From: Chris Albertson <albertson.chris at gmail.com>
>To: Bob Stewart <bob at evoria.net>; Discussion of precise time and frequency measurement <time-nuts at febo.com> 
>Sent: Saturday, November 9, 2013 11:08 AM
>Subject: Re: [time-nuts] Computing GPS Distance Error in Time
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>If you are dealing with positions that are only up to 5,000 feet distance, you can assume the Earth is flat and simply plot locations using maybe "gnuplot"  For such a small area the conversion of latitude and longitude to (x,y) is linear.    
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>Over larger areas you may want to integrate your data with maps and need access to function to compute bearing angles and distances  on a spheroid which is non-trivial.  GIS software like GQIS allows you to plot data on the Earth's surface.
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>On Thu, Nov 7, 2013 at 10:41 AM, Bob Stewart <bob at evoria.net> wrote:
>
>Hi Mark,
>>
>>What I was hoping for was some canned software that will plot position on the display until told to clear it so I can get a visual.  I've tried foxtrotgps, but it clears its screen at any and every opportunity, so barring getting into the code that's not going to work.  But I can capture the position data from my Adafruit and add it to the plot I'm already doing for timing.  So that will work.
>>
>>thanks,
>>
>>bob
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>>>________________________________
>>> From: Mark Sims <holrum at hotmail.com>
>>>To: "time-nuts at febo.com" <time-nuts at febo.com>
>>>Sent: Thursday, November 7, 2013 12:14 PM
>>>Subject: [time-nuts] Computing GPS Distance Error in Time
>>
>>>
>>>
>>>I'm not using any special surveying software,  just some code that I wrote.  The controller box and remote box both have GPS units in them.  The controller periodically requests the remote unit's position and just calculates the vector distance/bearing between the two units.  The application was intended to work with the boxes spaced 50-5000 feet apart.   I was rather surprised how well they worked very close together.  The next step is to add a magnetic compass module to the controller box so that it can draw a map of the remote units in relation to the orientation of the controller box.
>>>--------------
>>>What type of real-time surveying software are you using?  I'm looking for surveying/plotting software for Linux to keep a close on the timing stability of my Adafruit.                          
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>-- 
>
>Chris Albertson
>Redondo Beach, California 
>
>