Updated Jan 15, 2006
ArcMap 9.x functional note: At the 9.x version of ArcMap, ESRI has actually included this function into the base install. Hold down the shift key while using the measure tool to return the geodesic distance. Make sure that your projection and/or geographic definition is defined correctly.
Geodesic or True Distance Tool calculates accurate distances over a sphere in any projection. This is crucial for large regions or global views where projection errors can be huge.
History:
Jan 15, 2006 - added in support for ArcMap 9.1.
Sep 29, 2004 - added in support for ArcMap 9.
bug squashed May 21, 2003 - fixes the tool from returning the shorestest distance on the line but between two the points.
bug squashed May 15, 2003 - fixes the tool from not turning on when an existing project was loaded.
Note: This tool will enable when a data frame has a geographic coordinate or projected coordinate system set.
True Distance was written by ESRI in response to a problem with the standard measurement tool in ArcMap 8.x. When using a geographic data, the distance is measured over a sphere defined by Earth. However, when setting a different sized body (i.e. Mars), ArcMap continues to use the Earth as the default. Again, this tool will also return the geodesic distance for a data frame with a projection set.
Installation:
This tools has been compiled for ArcMap version 8.1, 8.2, 8.3, and 9.0. The 9.0 version should still work for ArcMap 9.1. If not, let me know! All versions and code are inside the compressed volume. Make sure to use correct DLL version. Once the DLL is loaded (customize - add from file), find the "ArcGIS_8x" or "USGS" (for ArcMap9) catagory and drag the tool "True Distance" onto your favorite toolbar. The tool will enable when a data frame has a geographic coordinate or projected coordinate system set.
Search for planetary projections for predefined geographic planetary definitions.
version 3.2, Jan 15, 2006
Uploaded by Trent Hare
http://webgis.wr.usgs.gov
Astrogeology, USGS
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