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copied!<pre><code>Lat_to_Travel = CurLat - TargetLat Long_to_Travel = CurLong - TargetLong Time_to_Travel = ETA - now </code></pre> <p>If the distances are relatively small, it is probably <strong>ok to assume a linear progression on these three dimensions</strong> (*). You then need to decide on a number of intermediate position to display, say 10, and calculate each intermediate point accordingly</p> <pre><code>NbOfIntermediates = 10 // for example Lat_at_Intermediate(n) = CurLat + (1/NbOfIntermediates * Lat_to_travel) Long_at_Intermediate(n) = CurLong + (1/NbOfIntermediates * Long_to_travel) Time_at_Intermediate(n) = now + (1/NbOfIntermediates * Time_to_travel) </code></pre> <p>The most complicated in all this is to keep the units ok.</p> <p>( * ) <strong>A few considerations as to whether it is ok to assume a linear progression...</strong><br> Obviously the specifics of <strong>the reality of the physical elements</strong> (marine currents, wind, visibility...) may matter more in this matter than geo-spatial mathematics.<br> Assuming that the vehicle travels at a constant speed, in a direct line, it is [<em>generally</em>] <strong>ok to assume linearity in the Latitude dimension</strong> [well technically the earth not being exactly a sphere this is not fully true but damn close]. However, over longer distances that include a relatively big change in latitude, the angular progression along the longitude dimension is not linear. The reason for this is that as we move away from the equator, a degree of longitude expressed in linear miles (or kilometer...) diminishes. The following table should give a rough idea of this effect, for locations at various latitudes:<br></p> <pre> Latitude Length of a Degree Approximate examples (of longitude) in nautical miles 0 60 Kuala Lumpur, Bogota, Nairobi 20 56.5 Mexico city, Mecca, Mumbai, Rio de Janeiro 45 42.5 Geneva, Boston, Seattle, Beijing, Wellington (NZ) 60 30 Oslo, Stockholm, Anchorage AK, St Petersburg Russia </pre> <p>See this <a href="http://www.csgnetwork.com/degreelenllavcalc.html" rel="nofollow noreferrer"><strong>handy online calculator</strong></a> to calculate this for a particular latitude.<br> Another way to get a idea for this is to see that traveling due East (or West) at the lattitude of Jacksonville, Florida, or San Diego, California, it takes 52 miles to cover a degree of longitude; at the latitude of Montreal or Seattle, it takes only 40 miles.</p>

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