ebergman@isis.cs.du.edu (Eric Bergman-Terrell) (11/06/90)
DIST for the HP 48SX: Introduction: This program calculates the great circle distance in statute miles between two cities, given their latitude and longitude in degrees, minutes, and seconds format. Caveats: No correction is made for the Earth's equatorial bulge. USE THIS SOFTWARE AT YOUR OWN RISK. Method: EXPRESS LATITUDES NORTH OF THE EQUATOR AS POSITIVE NUMBERS, AND LATITUDES SOUTH OF THE EQUATOR AS NEGATIVE NUMBERS. EXPRESS LONGITUDES WEST OF GREENWICH AS POSITIVE NUMBERS, AND LONGITUDES EAST OF GREENWICH AS NEGATIVE NUMBERS. Convert the two latitudes and longitudes into spherical coordinate unit vectors. The smallest angle between the vectors is calculated by taking the inverse cosine of the vectors' dot product. Multiplying this angle by 60 yields the nautical miles between the two cities. Multiplying by 6080 and then dividing by 5280 yields statute miles. Setup: YOUR CALCULATOR MUST BE IN DEGREES MODE TO RUN THE PROGRAM. To get into degrees mode, use the DEG command. Example: Tokyo: 35d35'00" N 139d45'00" E Denver: 39d44'58" N 104d59'22" W Entering the following: 35.35 -139.45 39.4422 104.5922 DIST leaves 5800 on the stack. My almanac says that Denver is 5795 statute miles from Tokyo. Program: %%HP: T(3)A(R)F(.); \<< 0 0 \-> LATA LONA LATB LONB A B \<< -15 SF -16 SF 1 LONA HMS\-> 90 LATA HMS\-> - \->V3 'A' STO 1 LONB HMS\-> 90 LATB HMS\-> - \->V3 'B' STO A B DOT ACOS 60 * 6080 * 5280 / -15 CF -16 CF \>> \>> Size/Checksum: 275 bytes # 11808d checksum Eric Bergman-Terrell