[Qgis-user] Velocity Difference Calculation?

[Randal Hale]

The part of me that screams deadline thinks maybe you toss it into 
excel/calc and derive time then join that info back the distance 
portion. The minute I finished that sentence that might work for a few 
lines/distance - but you might have more than a few points/lines in the 
problem.

To quote a person I once knew "That's a thinker".




On 08/17/2014 06:34 PM, dean.walker151 at gmail.com wrote:
> Yeah, I’ve got a distance reference that covers the amount of distance 
> covered in the time from the last point.  I’m just missing the way to 
> actually do the calculation in the program.  I cant see a way to 
> compare a point to the one before it.
>
> Thanks!
> Dean
>
> Sent from Windows Mail
>
> *From:* Randal Hale <mailto:rjhale at northrivergeographic.com>
> *Sent:* ‎Sunday‎, ‎August‎ ‎17‎, ‎2014 ‎3‎:‎22‎ ‎PM
> *To:* dean.walker151 at gmail.com <mailto:dean.walker151 at gmail.com>, 
> qgis-user at lists.osgeo.org <mailto:qgis-user at lists.osgeo.org>
>
> I can think of a couple of ways you might be able to do this - but 
> considering I haven't done something like this before it's a guess.
>
> You can derive an interval in seconds I believe (referencing 
> http://nathanw.net/2012/06/30/better-date-and-time-support-in-qgis-expressions-and-styles/) 
> from the point data  - I'm assuming you have date and time (or at 
> least time).
>
> You could connect the points with a line (that would give you distance).
>
> I'm thinking this might be better accomplished in a database as 
> opposed to a shapefile (assuming shapefile).
>
> ...and I think I've just given you the most abstract assumed 
> non-answer ever.
>
> Lemme think on this one a bit more. Hopefully someone has a practical 
> answer.
>
> Randy
>
>
>
>
> On 08/17/2014 05:57 PM, dean.walker151 at gmail.com wrote:
>
>     Hi all,
>
>     I’m working on some point data that has been collected using a
>     combine in an agricultural field. Trying to figure out a way to
>     compare speed between the dropped points?  I’m not sure how to
>     start….can anyone help?
>
>     Thanks
>     Dean
>
>
>     Sent from Windows Mail
>
>
>
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