[GRASS-dev] Re: [GRASS-user] measuring line sinuosity in GRASS

[Wolf Bergenheim]

On 04.01.2008 17:32, Duffy, Garret wrote:
> Hi GRASS-grazers,
> 
> I'm wondering if anyone out there has a script or has done any sinuosity 
> measurements on vector lines?
> 

Hi Garret,

I don't really have a script, but thought it would be a logical thing to 
add to the v.to.db module.

> I have a map with a number of quasi-parallel vector lines and I would 
> like to do sinuosity measurements (line length divided by node-to-node 
> straight-line distance) on each line separately.  I guess the ideal 
> output would be the same vector map but now with the sinuosity attribute 
> attached to each line.

I suppose you mean line length divided by the distance of the end nodes. 
That is at least what I have implemented.

> 
> Does anyone have any thoughts on how to do this?

I have added the option=sinuous to the v.to.db module, as it would be 
annoying at least to do it by hand or by script. To do it you'd first 
have to use v.to.db option=length, and then v.to.db option=start and 
v.to.db option=end Then do an update which would do the calculation. And 
if you use the DBF engine (which can't do [advanced] arithmetics), well 
then you'd have to do a select to get the values and then an update with 
the value calculated in the script.

Anyway, I have just committed changes to the SVN, and so maybe it will 
be merged to the next release?

Anyway I've attached the diff for your convenience. I hope you enjoy it :)

--Wolf

-- 

<:3 )---- Wolf Bergenheim ----( 8:>

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