# st: ST: vincenty formula for Africa

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## st: ST: vincenty formula for Africa

 Dear all, I am trying to find out abotu those distances, and apparently somethign went wrong with the conversion and the distmatch formula, so I am thinkin abotu trying the vincenty. I am not experienced wiht programming,... may I ask if someone knows  how to modify the vincenty command for Africa, using Clarke 1880 ellipsoid value? From:http://www.movable-type.co.uk/scripts/latlong-vincenty.htmlThe most accurate and widely used globally-applicable model for the earth ellipsoid is WGS-84, used in this script. Other ellipsoids offering a better fit to the local geoid include Airy (1830) in the UK, International 1924 in much of Europe, Clarke (1880) in Africa, and GRS-67 in South America. America (NAD83) and Australia (GDA) use GRS-80, functionally equivalent to the WGS-84 ellipsoid.   WGS-84 a = 6 378 137 m (±2 m) b = 6 356 752.3142 m f = 1 / 298.257223563   GRS-80 a = 6 378 137 m b = 6 356 752.3141 m f = 1 / 298.257222101   Airy (1830) a = 6 377 563.396 m b = 6 356 256.909 m f = 1 / 299.3249646   Intl 1924 a = 6 378 388 m b = 6 356 911.946 m f = 1 / 297   Clarke (1880) a = 6 378 249.145 m b = 6 356 514.86955 m f = 1 / 293.465   Laura * *   For searches and help try: *   http://www.stata.com/help.cgi?search*   http://www.stata.com/support/statalist/faq*   http://www.ats.ucla.edu/stat/stata/
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## RE: st: ST: vincenty formula for Africa

 > I am trying to find out abotu those distances, and apparently somethign went wrong with the > conversion and the distmatch formula, so I am thinkin abotu trying the vincenty. You can try -vincenty- by Austin Nichols from ssc. I am sure he will be able to help you integrate it into one of his codes.   For the record, the outputs produced by -distmatch- has been validated by Austin.   Roy   _________________________________________________________________ Your E-mail and More On-the-Go. Get Windows Live Hotmail Free. http://clk.atdmt.com/GBL/go/171222985/direct/01/* *   For searches and help try: *   http://www.stata.com/help.cgi?search*   http://www.stata.com/support/statalist/faq*   http://www.ats.ucla.edu/stat/stata/
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## RE: st: ST: vincenty formula for Africa

 > For the record, the outputs produced by -distmatch- has been validated by Austin. > > Roy   I was able to say that much sooner than I thought.   For those who of us who are not as fortunate, you can still validate your distance calculations at the following websites:   http://www.csgnetwork.com/gpsdistcalc.htmlhttp://gpsvisualizer.com/calculators  Roy   _________________________________________________________________ Ready for Fall shows? Use Bing to find helpful ratings and reviews on digital tv's. http://www.bing.com/shopping/search?q=digital+tv's&form=MSHNCB&publ=WLHMTAG&crea=TEXT_MSHNCB_Vertical_Shopping_DigitalTVs_1x1* *   For searches and help try: *   http://www.stata.com/help.cgi?search*   http://www.stata.com/support/statalist/faq*   http://www.ats.ucla.edu/stat/stata/
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## Re: st: ST: vincenty formula for Africa

 In reply to this post by Roy Wada Roy-- Please do not quote me as having validated your output--I have not done anything of the kind. Quite the contrary--I have requested that you make a correction in your package. On Sun, Sep 13, 2009 at 2:04 PM, Roy Wada <[hidden email]> wrote: >> I am trying to find out abotu those distances, and apparently somethign went wrong with the >> conversion and the distmatch formula, so I am thinkin abotu trying the vincenty. > > > You can try -vincenty- by Austin Nichols from ssc. I am sure he will be able to > help you integrate it into one of his codes. > > For the record, the outputs produced by -distmatch- has been validated by Austin. > > Roy * *   For searches and help try: *   http://www.stata.com/help.cgi?search*   http://www.stata.com/support/statalist/faq*   http://www.ats.ucla.edu/stat/stata/
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## Re: st: ST: vincenty formula for Africa

 In reply to this post by Roy Wada Roy-- Please do not quote me as having validated your output--I have not done anything of the kind. Quite the contrary--I have requested that you make a correction in your package. On Sun, Sep 13, 2009 at 2:56 PM, Roy Wada <[hidden email]> wrote: >> For the record, the outputs produced by -distmatch- has been validated by Austin. >> >> Roy > > > I was able to say that much sooner than I thought. > > For those who of us who are not as fortunate, you can still validate your distance > calculations at the following websites: > > http://www.csgnetwork.com/gpsdistcalc.html> http://gpsvisualizer.com/calculators> > Roy > * *   For searches and help try: *   http://www.stata.com/help.cgi?search*   http://www.stata.com/support/statalist/faq*   http://www.ats.ucla.edu/stat/stata/
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## RE: st: ST: vincenty formula for Africa

 In reply to this post by Austin Nichols > Roy-- > Please do not quote me as having validated your output--I have not > done anything of the kind. Quite the contrary--I have requested that > you make a correction in your package. Should someone be able to publicly request a correction in someone else's package when it clearly does not affect that person? Is there a gross scientific falsehood not consistent with good research? Have I caused an unconscionable loss or damages to someone as a result of my package? Did I steal codes out of someone's programs and misrepresented myself as the author?   I am trying to understand Austin's position here.   What it says in the help file is not important to me.   If Austin thinks it will greatly improve the package, then I am open to a revision. He can post a revised version help file here or send it to me privately.   The current version says the following:     distmatch provides a fast and easy way to perform distance matching based     on latitudes and longitudes. It mathces location identifiers, attributes,     or distances from one to another. It also counts the number of     neighboring locations within a given area, either in circles or bands of     concentric circles.       Outputs produced by distmatch are typically used in studies of geocoded     data. These outputs can also be produced by non-Stata softwares such as     ArcGIS and ArcView.       distmatch implements haversine formula for distance. The default is in     miles.       Distance matching is computationally intensive. Observations of 3,000 may     take several minutes to complete.  Other methods typically take days if     not weeks and requires extensive user-involvement. Roy _________________________________________________________________ Ready for Fall shows? Use Bing to find helpful ratings and reviews on digital tv's. http://www.bing.com/shopping/search?q=digital+tv's&form=MSHNCB&publ=WLHMTAG&crea=TEXT_MSHNCB_Vertical_Shopping_DigitalTVs_1x1* *   For searches and help try: *   http://www.stata.com/help.cgi?search*   http://www.stata.com/support/statalist/faq*   http://www.ats.ucla.edu/stat/stata/
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## Re: st: ST: vincenty formula for Africa

 In reply to this post by Laura Platchkov All-- In response to a private query, I sent Laura a draft revision of -vincenty-early this morning that will use any of these ellipsoids; in Stata, type   net from http://www-personal.umich.edu/~nicholsa/statato get it.  She told me she was not using Stata today, so she would try it out another day. I doubt the issue is really one of choice of ellipsoidal or spherical approximation; I suspect she is computing distances from farms to random points (one on each lake), judging from other questions on the Statalist.  As I told her privately, that will often be worse than using the centroids of lakes, but if she has the shapefile she can compute the distance to the nearest vertex.  That approach would also work for rivers, if she had a shapefile for rivers. Perhaps her calculations are failing because the latitudes and longitudes are not in the same format in both datasets, i.e. signed decimal degrees--I have not investigated that possibility. On Sun, Sep 13, 2009 at 8:22 AM, Laura Platchkov <[hidden email]> wrote: > Dear all, > > I am trying to find out abotu those distances, and apparently somethign went wrong with the conversion and the distmatch formula, so I am thinkin abotu trying the vincenty. > > I am not experienced wiht programming,... may I ask if someone knows  how to modify the vincenty command for Africa, using Clarke 1880 ellipsoid value? > > From:http://www.movable-type.co.uk/scripts/latlong-vincenty.html> > The most accurate and widely used globally-applicable model for the earth ellipsoid is WGS-84, used in this script. Other ellipsoids offering a better fit to the local geoid include Airy (1830) in the UK, International 1924 in much of Europe, Clarke (1880) in Africa, and GRS-67 in South America. America (NAD83) and Australia (GDA) use GRS-80, functionally equivalent to the WGS-84 ellipsoid. >        WGS-84  a = 6 378 137 m (±2 m)  b = 6 356 752.3142 m    f = 1 / 298.257223563 >        GRS-80  a = 6 378 137 m         b = 6 356 752.3141 m    f = 1 / 298.257222101 >        Airy (1830)     a = 6 377 563.396 m     b = 6 356 256.909 m     f = 1 / 299.3249646 >        Int’l 1924      a = 6 378 388 m         b = 6 356 911.946 m     f = 1 / 297 >        Clarke (1880)   a = 6 378 249.145 m     b = 6 356 514.86955 m   f = 1 / 293.465 > > Laura * *   For searches and help try: *   http://www.stata.com/help.cgi?search*   http://www.stata.com/support/statalist/faq*   http://www.ats.ucla.edu/stat/stata/