(20S and 21S) Great Circle
06-03-2017, 08:42 PM
Post: #1
 Eddie W. Shore Senior Member Posts: 1,198 Joined: Dec 2013
(20S and 21S) Great Circle
The following program calculates the distance between two places on Earth (or any other planet) given the coordinates latitude (λ, east is positive) and longitude (ϕ, north is positive).

Inputs:
R1: longitude 1, R2: latitude 1
R4: longitude 2, R5: latitude 2
Enter the coordinates in DD.MMSSSS.

R1, R4: ϕ1, ϕ2; R2, R5: λ1, λ2

Distance, in miles, is stored in R0. Degrees mode is set.

Formula:

distance = acos( sin ϕ1 * sin ϕ2 + cos ϕ1 * cos ϕ2 * cos (λ2 – λ1) )* 3958.75 * π/180

On the HP 20S and HP 21S, can multiply by π/180 by executing the >RAD function.

HP 20S and HP 21S Program: Great Circle
Code:
 STEP    CODE    KEY 01    61, 41, A    LBL A 02    61, 23     DEG 03    22, 1    RCL 1 04    51, 54    >HR 05    21, 1    STO 1 06    23    SIN 07    55    * 08    22, 4    RCL 4 09    51, 54    >HR 10    21, 4    STO 4 11    23    SIN 12    75    + 13    22, 1    RCL 1 14    24    COS 15    55    * 16    22, 4    RCL 4 17    24    COS 18    55    * 19    33    ( 20    22, 2    RCL 2 21    51, 54    >HR 22    21, 2    STO 2 23    65    - 24    22, 5    RCL 5 25    51, 54    >HR 26    21, 5    STO 5 27    34    ) 28    24    COS 29    74    = 30    51, 24    ACOS 31    55    * 32    3    3 33    9    9 34    5    5 35    8    8 36    73    . 37    7    7 38    5    5 39    74    = 40    61, 55    >RAD 41    21, 0    STO 0 42    61, 26    RTN

Example 1:
Los Angeles to Rome:
Los Angeles (ϕ1 = 34°13’, λ1 = -118°15’)
Rome (ϕ2 = 41°15’, λ2 = 12°30’)
Result: 6322.2196 mi

Example 2:
Dublin to Las Vegas:
Dublin (ϕ1 = 53°20’52”, λ1 = -6°15’35”)
Las Vegas (ϕ2 = 36°10’30”, λ2 = -115°08’11”)
Result: 4938.7520 mi
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 Messages In This Thread (20S and 21S) Great Circle - Eddie W. Shore - 06-03-2017 08:42 PM RE: (20S and 21S) Great Circle - Marcel - 06-03-2017, 10:00 PM RE: (20S and 21S) Great Circle - Dieter - 06-04-2017, 03:37 PM

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