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@@ -1,9 +1,41 @@ gridcal -- compute the great-circle distance between two grid locators ====================================================================== -`gridcal` computed the short-path great-circle distance between two grid +`gridcal` computes the short-path great-circle distance between two grid locators. The Grid Locator System divides Earth into a series of rectangles identified by a combination of letters and numbers, so that the approximate position of a point can be expressed with a short identifier like IO91vl. +Usage: gridcal <loc1> [<loc2> [<pwr>]] + +If `gridcal` is given only one locator, it prints on output the latitude +and longitude of the centre of the corresponding grid square: + + gridcal IO91vl + IO91vl 51.4792 -0.208333 0.898481 -0.0036361 + +With two locators as input, `gridcal` prints on output the two locators +and their great-circle distance, both in km and miles: + + gridcal IO91vl JN65od + IO91vl JN65od 1213.71 754.164 + +If `gridcal` is given as third numerical argument, that number is +considered a "power" value in Watts, and `gridcal` will print on output +a longer line containing the two locators, the distance in km and miles, +the power value, and the corresponding km/W and miles/W: + + gridcal IO91vl JN65od 1.2 + IO91vl JN65od 1213.71 754.164 1.2 1011.42 628.47 + +The latter can be useful to check if a QSO with another ham radio +station qualifies for one of the thousand miles per Watt awards. + + +Dependencies +============ + +`gridcal` is written in ANSI C has no dependencies. + + |