Sv: Re: Sv: Re: [Qgis-user] Creating polygon from points in csv file

Tue May 25 11:59:13 PDT 2010

Hello Goyo,

I see I made a bad choice of sample file. The Z is the same in 
polygons because they represent small buildings. To create them the 
corners of the roofs were measured in the stereomodel resulting in the 
same z values. Of course a lot of objects have a common Z like lakes 
and shorelines and many others. The more general case is that Z i 
varying from ponint to point in the polygon or line. Think of polygons 
representing landuse or cadstral divisons or lines representing streams 
or roads. In this simple file structure a line looks like this:

STOLP  1868536.305  7323297.568  5.206  21
STOLP  1868514.063  7323234.352  2.558  22
STOLP  1868445.482  7323050.904  3.220  22
STOLP  1868514.063  7323234.352  2.558  23

The polygon differs rom the line in that the points with pencode 21 &v 
23 have the same coordinates indicating the closure. Point have the 
pencode 11 indicating no connection:

AHP,1868280.000,7323450.000,0.271,11
AHP,1868300.000,7323450.000,1.324,11
AHP,1868320.000,7323450.000,0.542,11

I tried to get those files into Qgis but with no complete succes. There 
is one plug in redings csv files ok but i does not take care of the 
topology and only reads X & Y.

Best regards

Ulf

----Ursprungligt meddelande----
Från: goyodiaz at gmail.com
Datum: 2010-05-24 22:35
Till: "Ulf Almroth"<ulf.almroth at lillabjoern.se>
Kopia: "MORREALE Jean Roc"<jr.morreale at enoreth.net>, "qgis-user List"
<qgis-user at lists.osgeo.org>
Ärende: Re: Sv: Re: [Qgis-user] Creating polygon from points in csv 
file

Hello Ulf,

El sáb, 22-05-2010 a las 00:01 +0200, Ulf Almroth escribió:
> Hi,
> 
> Using an attribute is agood idea. A lot of measuring devices 
> generating ascii files with coordinates, e.g. various type of 
surveying 
> equipment and coordinate measuring devices 
> for industrial use produces file that basically look like this:
> 
> featuretyp, X,Y,Z,pencode
> 
> A sample file from a steroplotter used for mapping arial images with 
> sterooverlpa looks like this:
> 
> BBH  1868462.502  7323256.557  5.266  21
> BBH  1868458.596  7323265.540  5.266  22
> BBH  1868452.062  7323262.698  5.266  22
> BBH  1868455.967  7323253.716  5.266  22
> BBH  1868462.502  7323256.557  5.266  23
> BBH  1868359.027  7322916.789  6.259  21
> BBH  1868357.951  7322925.557  6.259  22
> BBH  1868351.513  7322924.767  6.259  22
> BBH  1868352.589  7322915.999  6.259  22
> BBH  1868359.027  7322916.789  6.259  23
> 
> where   21  signifies the styart of the polygon (or line) and 23 the 
> end.

Since the points are sorted you can just group by the Z field. Then you
get two polygons in this example without the need to look at the
pencode. Or maybe it's not as simple as I think?

I don't want to clutter the interface with more options without an use
case which makes them necessary.

Goyo

> 
> Regards 
> 
> Ulf Almroth
> 
> 
> ----Ursprungligt meddelande----
> Från: goyodiaz at gmail.com
> Datum: 2010-05-20 00:03
> Till: "MORREALE Jean Roc"<jr.morreale at enoreth.net>
> Kopia: "qgis-user List"<qgis-user at lists.osgeo.org>
> Ärende: Re: [Qgis-user] Creating polygon from points in csv file
> 
> El mié, 19-05-2010 a las 22:20 +0200, MORREALE Jean Roc escribió:
> > Hi Goyo,
> > 
> > I would like to test your file but I can't not extract the file 
from 
> the 
> > tar.bin, could you resend it using a more common format ?
> 
> The original author, Pavol Kapusta, uploaded (a new version of) it to
> the contributed repository so you should be able to install it using 
> the
> plugin installer (plugins > Install python plugins).
> 
> Please send bug reports and suggestion here or to me.
> 
> > 
> > Your modification is great as it would solve a major pain I've 
been 
> > dealing with my tacheometer's output, it is a basic ascii file 
where 
> > every record is a point to which you can append a codification.
> > 
> > For now we've to connect the point by hand, automating this task 
> would 
> > be a relief (and a lot less error prone).
> > 
> > Would it be easier to make a correct geometry by assigning a code 
to 
> the 
> > point telling if it's the opening or the closure ? Or just 
following 
> the 
> > incrementing point number would be enough to get a correct geometry 
?
> 
> As for now the plugin assumes the points are in the proper order.
> Sorting them by an attribute sounds like a good idea to me, I'?l 
think
> about it.
> 
> Goyo
> 
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