Re: how to calculate the area of polygon?

Dir Sir
According to your suggestion, 
I tried to do the script below to calculate the area of the polygon with gmtspatial, but the result is strange as unexpected.
Could you tell me how to solve the problem?

gmtspatial poly.data -Q
poly.data is like 20:00  -50:00 20:00  -60:00 10:00  -60:00 10:00  -50:00
regards,
takaya

Date: Thu, 28 Nov 2013 15:48:05 +0100
From: [email protected]
Subject: Re: [GMT-HELP] how to calculate the area of polygon?
To: [email protected]


  
    
  
  
    In GMT5 you can do this using gmtspatial, 

    

    If you are stuck with GMT4 it should be possible to do so using
    grdvolume if you first define a grid file in which all the points
    inside your polygon has a constant value differing from the points
    outside, then apply grdcontour to the countour value equal to the
    value you have chosen inside your polygon.  

    

    regP 

    

    

    On 11/28/2013 03:35 PM, Namba Takaya
      wrote:

    
    
      
      
      Dear sir
        

        
        

        
        Could you tell me how to calculate the area of polygon(hour
          points) like
        

        
        1.   5:00E  55:00S 
        2.   6:00E  55:00S
        3.   6:00E  56:00S
        4.   5:00E  56:00S
        

        
        regards,
        

        
        takaya
      
    
    

    -- 
********************************************************************************
Peter Schmidt                                      Tel: +46-18-4717104
Swedish National Seismological Network (SNSN)   Mobile: +46-73-3190975
Dept. of Earth Sciences:geophysics              e-mail: [email protected]  
Uppsala University
Villavagen 16
SE-75236 Uppsala
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