Re: Re[2]: New ground proximity warning.

Date:         27 Dec 96 04:41:06 
From:         dmarble@magnus.acs.ohio-state.edu (Duane F Marble)
Organization: The Ohio State University
References:   1 2 3 4
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Digital terrain models by definition do not contain man-made features
unless you are including features such as railway cuts, etc. They are
an approximation of the continuous surface of the terrain and, as such,
subject to errors that arise in the chain from original observation to
map to digital form.

Pre-GPS CM navigation was based upon matching a linear terrain profile
to the two-dimensional surface (an approach originally developed by
Dr. Herbert Freeman many years ago). The fewer features in the terrain
(e.g., portions of Siberia) the more difficult the matching task and
the poorer the resultant position.

--
Duane F. Marble               E-mail: marble.1@osu.edu
Department of Geography       Telephone: (614) 292-2250
The Ohio State University     Fax: (614) 292-6213
Columbus, Ohio 43210          Home Page: http://thoth.sbs.ohio-state.edu