NavList:

Greg, GPS?, Navigator?, with all lost at sea, :-)

I use the Sight Reduction with calculator, Form & Plotting sheet for celestial LoPs at http://www.geocities.com/andresruizgonzalez/marinenavigation.html for manually SR, but this takes a lot of time, and is prone to errors, and I prefer to use the programs written by me aboard an 8 m sailboat. I am an engineer and for me the time of table and abacus has gone, yes astronavigation but with 21^st century tools, why not?.

In Spain, in order to obtain the captain license for a private yacht, you have to pass an exam that includes Celestial navigation, naval kinematics, rhumb line and GC sailings,… and of course you can use tables, but the people usually prefers a non programmed calculator.

I have found people that uses the almanac and the tables as a cook recipe, yes they reach a fix, but really they don’t know what are they doing.

Well ---

For time for Pollux UT1: 21:00:50

The solution is:

34º 13.3' N 119º 16.6' W, both, solving for 3 LoP, (DeWit , LopLSSR), and solving for 3 CoP, (Circles of Position or Circles of Equal Altitude, Kaplan)

Navigator: I think the method it uses is not the best, is a manually approximation.

For anyone who wants to do manual calculations, the LoP of Pollux is:

Fecha y hora UT1

09/06/2008

04:00:50

SITUACION ESTIMADA

Latitud: Be = 34.216667 º =  34º 13.0'

Longitud: Le = -119.316667 º = -119º 19.0'

ALMANAQUE NAUTICO

Cuerpo celeste: Estrella Pollux

Polo de iluminacion del astro: Coordenadas Ecuatoriales

GHA = 201.652447 º = 201º 39.1'

Dec = 28.007559 º =  28º  0.5'

Correcciones altura:

SD  = 0.000000 '

HP  = 0.000000 '

CORRECION DE LA ALTURA

altura sextante [º]: Hs = 21.2583  =  21º 15.5'

correcion de indice [']: ie = 0.0000

altura del ojo sobre el nivel del mar [m]: heas = 6.0960

temperatura ambiente [ºC]: T = 10.0000

presion atmosferica [mb]: P = 1010.0000

en [º]:

altura observada por el sextante: Hos = 21.2583

depresion del horizonte: dip = 0.0724

altura aparente: Ha = 21.1859

correcion por refraccion: R = 0.0418

correcion por achatamiento: OB = 0.0000

Paralaje horizontal: HP = 0.0000

correcion por paralaje: PA = 0.0000

semidiametro: SD  = 0.0000

Augmentation of SD = 0.0000

altura observada corregida: Ho = 21.1441 =  21º  8.6'

DETERMINANTE DE LA RECTA DE ALTURA

Angulo Horario Local: LHA = 82.335781 º =  82º 20.1'

Coordenadas Horizontales: Hc, Z

Altura Calculada: Hc = 21.1880 º =  21º 11.3'

Azimut: Z = 290.2 º

p = Ho-Hc = -0.043838 º = -2.630267 '

(Here s/e is the DR position, and s/v is the true one). I have attached the input file for this program.

Greg, the Celestial Fix program is developer by me, and is gratis at my website.

The Plot CoP pushbutton call a program that plot on a shoreline Mercator chart the Circles of Position. The interface is from the NavList member Michael Dorl, and the algorithms is by me using vectors instead of spherical trigonometry.

Andrés

-----Mensaje original-----
De: NavList@fer3.com [mailto:NavList@fer3.com] En nombre de Greg R.
Enviado el: martes, 10 de junio de 2008 21:58
Para: NavList@fer3.com
Asunto: [NavList 5392] [SOLUTION] Re: [NavList 5391] RE: 3-Star Fix - "Canned Survival Problem"

--- Andres Ruiz <aruiz@orona.es> wrote:

>  34º 11.0' -119º 9.9'

Hi Andres:

Your solution is accurate to within a few miles (actual GPS position is

34°14.4’N / 119°15.9’W), and the intrepid navigator thanks you for the

timely rescue. :-)

But I think you missed this part of the problem: "the navigation

computer and calculators were all lost at sea" (unless you really want

us to believe that you can do the spherical trigonometry calculations

to 15-16 decimal point accuracy manually...).  ;-)

That being said, I do like the look of the user interface that you

attached (especially the fact that it shows the circles of position on

a small scale map) - what program is that?

Interestingly enough, Navigator gives a position of 34° 12.6'N / 119°

16.5'W, so I guess the programs all use slightly different computation

methods to arrive at a solution.

--

GregR