The Case for Using the Spherical Model to Calculate the Interpolated Points in the Connectivity Software Deployment Module

Report No. ARL-TR-4373
Authors: G. Welles Still and James F. Nealon
Date/Pages: February 2008; 55 pages
Abstract: A new software package undergoing development through joint efforts by the Missile Defense Branch at Aberdeen Proving Ground, Maryland, and the Communications Electronic Warfare Branch at Fort Monmouth, New Jersey, of the U.S. Army Research Laboratory's (ARL) Survivability/Lethality Analysis Directorate models and predicts the viability of communications links between moving nodes. Interpolation calculations will be needed to predict the location of the moving nodes between user-provided way points. The developers must decide which model of the earth to use as the basis of the calculations. Thus, a comparison was made between the National Geodetic Survey-provided computer programs Forward an Inverse based on the WGS84 Oblate Spheroid (OS) model, and a newly constructed program based on a Perfect Sphere (PS). The basis of the comparison was computational accuracy and speed. For a way point separation of 100 km or less, the maximum PS and WGS84 OS discrepancy was 1 meter¿accurate enough for link budget applications. When Forward and Inverse were kept intact and ran from a batch file, it took 30 times longer to do the same calculations as the PS model. When Forward and Inverse were modified to compute efficiently, it took 1.5 times longer. To modify the OS codes took 2.5 times as long as it did to write the PS code. Based on these results, it is recommended that the PS model for the earth be used.
Distribution: Approved for public release
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Last Update / Reviewed: February 1, 2008