[Gvsig_english] negative values of polygon area

ernesto sferlazza e.sferlazza at gmail.com
Thu Jun 9 13:30:49 CEST 2011


Hello developers, apologize me, since this issue is not new, but I
think that this is a bug and needs to be resolved.
When I perform the area calculations on polygons, the calculated
values may result positive or negative, dependig if polygon vertices
were digitized clokwise or counter-clockwise.
Skilled users  don't have problems in calculating absolute values of
area, since they can use the "abs( )" function, but I think that would
be best to obtain positive values of area using directly the "area"
function.
Furthermore, when the area field is automatically added (with all
calculated values) to the attribute table using "add geometric info",
the user is forced to recalculate (using "abs" funcion) all values.
And what happens for polygons with holes?
Best regards
Ernesto Sferlazza

-- 
ing. Ernesto Sferlazza
responsabile nodo provinciale di Agrigento del SITR Sicilia
resp. gruppo Sistema Informativo Territoriale
Provincia regionale di Agrigento
sede istituzionale: piazza Aldo Moro, 1 - 92100 AGRIGENTO
sede operativa: via Acrone, 27 - 92100 AGRIGENTO
cell. 3392718463 (personale)
       3316874296 (aziendale)
tel. uff 0922593752


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