Area measurement

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Area measurement

Postby Ing. David » Tue Feb 09, 2010 4:28 am

is there a way to draw something and measure:
a) length
b) area
c) angle

thank you very much!
David openoffice 3.1.0 on windows vista
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Re: area measurement

Postby acknak » Tue Feb 09, 2010 5:01 am

Not really, although you can get some of those values, with some restrictions.

If you want to describe a specific situation, maybe we can make some specific suggestions.
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Re: Area measurement

Postby Ing. David » Tue Feb 09, 2010 10:08 am

autocad has a measure area measure length measure angle feature
is there a way to maybe transform drawing to .dwg and measureitwith the autocad reader?
blau azotea trasera.odg
had to draw triangles and rectangles calculate areas and add
(16.81 KiB) Downloaded 202 times
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Re: Area measurement

Postby acknak » Tue Feb 09, 2010 6:39 pm

Ok; thanks for the sample.

Draw is really not good for CAD or engineering drawing. I would consider any sort of analysis done with it as "approximate". It just isn't designed for that kind of work and there are still problems with its coordinate system and scaling that can give incorrect values.

That said, it is possible to do some simple calculations on Draw figures, as you've done, or using extensions that are available. Here's one that I've heard of, but not tried myself:
http://extensions.services.openoffice.o ... ect/cadooo

You may also want to look at these previous threads:
viewtopic.php?f=11&t=21044
viewtopic.php?f=11&t=24101

There's another extension linked there that allows you to extract information from Draw into a spreadsheet, where you can do whatever calculations you want.

BTW, in your diagram, are you interested in the entire area of the large, 4-sided shape, or of (some subset of) the smaller colored polygons within the larger one? I find an area of about 117 m^2 for the large area.
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Re: Area measurement

Postby Lubos Raus » Wed Jan 23, 2019 2:22 pm

I can offer the procedure for area measurement of polypolygon (i use it in OpenOffice Draw):
Lubos Raus

Code: Select all   Expand viewCollapse view
Option Explicit
' Copyleft 2019 Lubos Raus
' Procedure is based on https://forum.openoffice.org/en/forum/viewtopic.php?f=11&t=86532

Sub PolygonArea

Dim oDoc As Object, PolyPolygonShape As Object
Dim StartPoint As New com.sun.star.awt.Point
Dim Value as Long, PointsNumber as integer, i as Integer, InputStr as String

   oDoc = ThisComponent
   If IsNull(oDoc) Then
      Exit Sub
   EndIf

   PolyPolygonShape = MyGetCurrentlySelectedSingleShape(oDoc, False)
   If IsNull(PolyPolygonShape) then
      exit sub
   End if
   
   If PolyPolygonShape.getShapeType() <> "com.sun.star.drawing.PolyPolygonShape" Then
      MsgBox "Selected shape is not PolyPolygonShape", 48, "Info"
      exit sub
   End if
   
   PointsNumber = UBound(PolyPolygonShape.PolyPolygon(0))
   
Dim Points(PointsNumber) As New com.sun.star.awt.Point
Dim Coordinates(0 to PointsNumber, 0 to 1) as Long
   Array(Points()) = PolyPolygonShape.PolyPolygon
   For i= 0 to PointsNumber
     Coordinates(i,0) = PolyPolygonShape.PolyPolygon(0)(i).x
     Coordinates(i,1) = PolyPolygonShape.PolyPolygon(0)(i).y
   next i
   
Dim x(PointsNumber) as Double, y(PointsNumber) as Double, Area as Double
   Area = 0
   For i= 0 to PointsNumber
     x(i) = Coordinates(i,0)/1000
     y(i) = Coordinates(i,1)/1000
   next i

   For i= 0 to PointsNumber-1              ' algortimus based on mathworld.wolfram.com/PolygonArea.html
     Area = Area + x(i)*y(i+1)-x(i+1)*y(i) ' (CRC Standard Mathematical Tables and Formulas 33E (2018).pdf pg. 212)
   next i
   Area = Area/2
   MsgBox "Polygon Area is:   " & Area & " cm².",0 , "Polygon Area"

End sub
'___________________________________________________________________________________________________________________

'**************************************************************************************
' Next functions based on Danny B's macro collection downloaded from the old oooForum.
' a version of the original code is available from this topic of the AOO forum:
' https://forum.openoffice.org/en/forum/viewtopic.php?f=7&t=15217&start=0
' and on this place:
' http://nab.pcug.org.au/20090204_bas_source/dannyb.bas
'**************************************************************************************

Function MyDrawingGetSelection(ByVal oDrawDocCtrl as object) as object

Dim oSelectedShapes as object
Dim oDrawDocCtrl2 as object

   If Not HasUnoInterfaces( oDrawDocCtrl, "com.sun.star.frame.XController" ) Then
      'xray oDrawDocCtrl       
      oDrawDocCtrl2 = MyGetDocumentController( oDrawDocCtrl )
   else
      oDrawDocCtrl2 = oDrawDocCtrl
   EndIf

   If IsEmpty( oDrawDocCtrl2.getSelection() ) Then
      oSelectedShapes = createUnoService( "com.sun.star.drawing.ShapeCollection" )
   else
      oSelectedShapes = oDrawDocCtrl2.getSelection()
   EndIf
   
MyDrawingGetSelection() = oSelectedShapes

End Function
'___________________________________________________________________________________________________________________

Function MyGetCurrentlySelectedSingleShape(ByVal oDrawDoc, Optional bSilent ) As Object

Dim oSelectedShapes as object
Dim oSingleSelectedShape as object

   If IsMissing( bSilent ) Then
      bSilent = False
   EndIf
   
   oSelectedShapes = MyDrawingGetSelection(oDrawDoc)
   If oSelectedShapes.getCount() <= 0 Then
      If Not bSilent Then
         MsgBox "There is not object selected", 48, "Info"
         Exit Function
      EndIf
   
   ElseIf oSelectedShapes.getCount() > 1 Then
      If Not bSilent Then
         MsgBox "Please select one shape only", 48, "Info"
         Exit Function
      EndIf   
   Else
      oSingleSelectedShape = oSelectedShapes.getByIndex(0)     
      myGetCurrentlySelectedSingleShape() = oSingleSelectedShape
   EndIf

End Function
'___________________________________________________________________________________________________________________

Function MyGetDocumentController( oDoc As Object ) As Object

Dim oCtrl As Object
   
   If oDoc.supportsService( "com.sun.star.document.OfficeDocument" ) Then
      oCtrl = oDoc.getCurrentController()
   ElseIf HasUnoInterfaces( oDoc, "com.sun.star.frame.XController" ) Then
      oCtrl = oDoc
   ElseIf HasUnoInterfaces( oDoc, "com.sun.star.frame.XFrame" ) Then
      oFrame = oDoc
      oCtrl = oFrame.getController()
   Else
      MsgBox( "GetDocController called with incorrect parameter." )
   EndIf
   
MyGetDocumentController() = oCtrl

End Function
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Re: Area measurement

Postby John_Ha » Wed Jan 23, 2019 3:38 pm

There are many free CAD packages which will calculate areas. Google for them.

See How to measure areas in map [using LibreCAD] - export an image and insert it into LibreCAD.

If you can break the area into triangles you can calculate it easily. If the sides are a, b and c, calculate S = (a+b+c)/2. The area is now sqrt[s * (s-a) * (s-b) * (s-c)]. See Heron's Formula.

area triangle.ods
(9.98 KiB) Downloaded 28 times

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Re: Area measurement

Postby Lupp » Thu Jan 24, 2019 1:10 am

I would not resort to Heron's formula here. In the context of drawing software e.g. polygons will next to always be described by coordinates of points and/or vectors, and next to never by side lengths (and angles). This should even hold for software accepting angles an lengths for input as soon as the input is processed.
Sticking to 2D the oriented area of a triangle is half the determinant of the 2 x 2 matrix formed by the 2 (column-) vectors describing two sides of the triangle in ordinary succession. For polygons without any pair of intersecting edges you don't need a triangulation at all.
See attached example. (Disclaimer: Errors expected.)
Attachments
aoo27311AreaOfPolygon_1.ods
(26.49 KiB) Downloaded 29 times
On Windows 10: LibreOffice 6.2 and older versions, PortableOpenOffice 4.1.5 and older, StarOffice 5.2
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