Example 3 - Midpoint Polyline

This example will demonstrate the use of the aqua “Poly-M” polyline by showcasing the formula for determining the “midpoint” between two different pairs of latitude/longitude coordinates. This Geomidpoint.com article explains in detail how a “geographic midpoint” formula works.
Irfanview screenshot
In the “Group” section of the LPanel, click on the green “yes” (Show Poly-M Polyline) radio button to display the aqua “Poly-M” polyline that will be aligned on top of the first half of the yellow “Poly-A” polyline, starting from the gold marker “V.”
Irfanview screenshot
To set a -90 degree bearing for the yellow “Poly-A” polyline—and a length of 3218.688 kilometers (2000 miles) from the polylines’ vertex (marker “V”) to the red end-marker “A”—click the green “A” button in the “Poly-A” section of the “Polys” section of the LPanel, then enter into the “Poly-A len” input box “3218.688” (the default setting is “kilometers” for the “Poly-A len” input box) and enter “-90” into the “Poly-A brg” (bearing) input box—then click the “Update Poly-A Lat/Lng” button.
Irfanview screenshot
In the “Poly-B” section, right below the “Poly-A” section, click on the green “yes” (Fit markers A, B, and V on screen) radio button so that the entire length of the yellow “Poly-A” polyline can be seen.
Irfanview screenshot
Again in the “Polys” section, click on the “OM” text-link to open the “Mini LPanel” in the upper-right of the Google map, to make marker “A” viewable on the Google map.

Irfanview screenshot
To set a -90 degree bearing for the yellow “Poly-B” polyline—and a length of 1609.344 kilometers (1000 miles) from the polylines’ vertex (marker “V”) to the red end-marker “B”—click the green “B” button in the “Poly-B” section of the Mini LPanel, then enter into the “Poly-B len” input box “1609.344” and enter “-90” into the “Poly-B brg” input box—then click the “Update Poly-B Lat/Lng” button.
Irfanview screenshot
Results: the straight/curved aqua “Poly-M” polylines sit right on top of the yellow/white “Poly-B” polylines’ paths, and are of the same length. You can observe this symmetry by clicking on the yellow “SLP” (Show Location Panel) button above the Mini LPanel, to open the LPanel, then going to the “Group” section and toggling the orange (Hide Poly-M Polyline) and green (Show Poly-M Polyline) radio buttons to remove, then add back, the aqua “Poly-M” polylines.
This example demonstrates that the shortest distance over the spherical Earth’s surface between marker “V” and marker “B” in the screenshot above mirrors the same path as the half-distance (or “geographic midpoint”) between marker “V” and marker “A,” along the white “geodesic” “Poly-A” polyline!

Continue to Example 4 (1 of 2)
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