[Gvsig_english] calculating centre points of polygon and ascribing coordinates

[Simon Cropper (Botanicus Australia Pty Ltd)]

Wolfgang,

Both options appear good. Thanks.

Side Note: -- Something else I have discovered is the "Add geometry 
info" allows you to insert the X-coordinate, Y-coordinate and 
Z-coordinate for point themes. I look at this tool yesterday when using 
a test polygon but did not note these options (just add area+perimeter). 
This cuts out creating a field and using the calculator.

I tested both options you suggested on a random set of polygons then 
used the "Add geometry info" and compared the output in the table. Both 
X and Y values were identical.

I will look forward to when the fully updated manual is released as I 
keep finding new things everyday with this software that are not noted 
or described in the old manual or the "What's New in 1.9" online manual.

Cheers Simon

Simon Cropper
Botanicus Australia Pty Ltd
PO Box 160, Sunshine, Victoria 3020.
P: 9311 5822. M: 041 830 3437.
mailto: scropper at botanicusaustralia.com.au 
<mailto:scropper at botanicusaustralia.com.au>
web: www.botanicusaustralia.com.au <http://www.botanicusaustralia.com.au>



Wolfgang Qual wrote:
> Hi Simon,
> well, I browsed a little bit and found an answer:
> you can export your polygon layer to an annotation layer (export to...
> annotation). Then edit this annotation layer (add x- and y-coordinates
> using the field calculator). 
>
> best,
> wolfgang
> Am Mittwoch, den 25.11.2009, 00:20 +1100 schrieb Simon Cropper
> (Botanicus Australia Pty Ltd):
>   
>> Hi,
>>
>> I have found some answers.
>>
>> First X, Y can be extracted with the field calculator using the 
>> functions x() and y().
>>
>> Sextante can be used to extract the centre point of a polygon.
>>
>> This aside is there any way of consolidating these tasks? Can you 
>> calculate the centre point of a polygon in gvSIG?
>>
>> Cheers Simon
>>
>> Simon Cropper
>> Botanicus Australia Pty Ltd
>> PO Box 160, Sunshine, Victoria 3020.
>> P: 9311 5822. M: 041 830 3437.
>> mailto: scropper at botanicusaustralia.com.au 
>> <mailto:scropper at botanicusaustralia.com.au>
>> web: www.botanicusaustralia.com.au <http://www.botanicusaustralia.com.au>
>>
>>
>>
>> Simon Cropper (Botanicus Australia Pty Ltd) wrote:
>>     
>>> Hi Everyone,
>>>
>>> Can someone tell me if gvSIG can be used to establish the centre point 
>>> of a polygon?
>>>
>>> ... and subsequently place the X and Y coordinates in fields in the 
>>> attribute table of the polygon shapefile?
>>>
>>> ... or alternatively create a point file representing the centrepoint 
>>> and be able to assign the XY values to that shapefile.
>>>
>>> What I regularly do in alternative programs (OpenJUMP, Kosmo, Sextante) 
>>> is create a point file showing the centrepoint of a set of polygons 
>>> (usually representing the sites I have surveyed) and then using ArcView 
>>> assign the XY coordinate of the points to the northing+easting fields. 
>>> Reproject into Lat-Long and repeat. These coordinates are used to report 
>>> the sites locations to government agencies.
>>>
>>> How would you do this in gvSIG?
>>>
>>> Can you use Jpython to do this?
>>>   
>>>       
>> _______________________________________________
>> Gvsig_internacional mailing list
>> Gvsig_internacional at listserv.gva.es
>> http://listserv.gva.es/cgi-bin/mailman/listinfo/gvsig_internacional
>>     
>
>
> _______________________________________________
> Gvsig_internacional mailing list
> Gvsig_internacional at listserv.gva.es
> http://listserv.gva.es/cgi-bin/mailman/listinfo/gvsig_internacional
>
>
>