Rainsford line (b), International ellipsoid * on the ellipsoid with application of nested equations, Survey Review 22(176): (1975) Direct and inverse solutions of geodesics * Duplicate all 5 examples Vincenty used to compare his results with those of Here's a small subset:Ĭode: * Choose to run this script under the executable versionĬscript "geodist - Stata version `c(stata_version)' " adofile geodist With respect to the validity of the results produced by my programs, I'm always happy to provide all certification scripts that I use upon request. That's because ArcGIS works with projected coordinate systems. I'm no expert on ArcGIS, but as far as I can tell, ArcGIS has historically calculated Euclidean distances between features. The Haversine and Laws of Cosine equations (which are mathematically equivalent) are used if the earth is modeled as a sphere. By default, the shape of the earth is approximated using the WGS 1984 reference ellipsoid (what GPS devices and Google Earth/Map use) and distances are computed using Vincenty's inverse solution equations. Both are available from SSC.Īs explained in detail in the help file, geodist calculates the length of the shortest curve between two points along the surface of a mathematical model of the earth.
I'm the author of geodist, which is a standalone version of the distance routines I wrote for geonear, a program that finds nearest neighbors using geodetic distances.
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