Using HP-65 Sunrise/Sunset

[Matt Agajanian]

Hi there. I have the Cuvee RPN-65 iOS app. I also have some questions.

As I remember from my SR-56 and TI-58C days, using nav programs meant longitudes and latitudes followed a sign convention (I think West and South were entered as negative numbers (at least for TI programs). For the 65 program I mentioned in the title and found at http://www.cuveesoft.ch/rpn65/p09.html#NAV1 in the Nav Pac program 16 , what is the sign convention for latitudes and longitude? Thank you.

[Geoff Quickfall]

Always EAST and SOUTH -ve.

Convention and the way the sin/cos great circle, intermediate latitude and rhumb line formula work. Re-check the TI program for sign convention. They must have a routine to change the sign because I am positive that all rhumb line and great circle formulae require EAST and SOUTH to be -ve.

Geoff

[Matt Agajanian]

If I'm reading your shorthand correctly, -ve means negative. Right?

[Geoff Quickfall]

Sorry, old school physics course -ve (negative). +ve (positive).

:-)

[Matt Agajanian]

(05-10-2017 03:18 AM)Geoff Quickfall Wrote:  Sorry, old school physics course -ve (negative). +ve (positive).

:-)

Well, now I know.

Thanks

[SlideRule]

(05-10-2017 01:12 AM)Geoff Quickfall Wrote:  ... all rhumb line and great circle formulae require EAST and SOUTH to be -ve.

From Navigation Spreadsheets "Our adopted sign convention marks north latitudes and east longitudes as positive; south latitudes and west longitudes are considered negative; hour angles increase in the westward direction."

The web site is lists the following references:
Jean Meeus, Astronomical Algorithms, Second Edition, Willmann-Bell (2005).
Nautical Almanac, 2009 Commercial Edition, UK Hydrographic Office (2008).
Nautical Almanac, 2010 Commercial Edition, UK Hydrographic Office (2009).
Nautical Almanac, 2011 Commercial Edition, UK Hydrographic Office (2010).
Nautical Almanac, 2012 Commercial Edition, UK Hydrographic Office (2011).
Nautical Almanac, 2013 Commercial Edition, UK Hydrographic Office (2012).
Nautical Almanac, 2014 Commercial Edition, UK Hydrographic Office (2013).
Nautical Almanac, 2015 Commercial Edition, UK Hydrographic Office (2014).
Nautical Almanac, 2016 Commercial Edition, UK Hydrographic Office (2015).
Nautical Almanac, 2017 Commercial Edition, UK Hydrographic Office (2016).
The Astronomical Almanac for the year 2009, The Stationery Office, United Kingdom (2007).
Explanatory Supplement to the Astronomical Almanac, Univ. Science Books (2006).
The American Practical Navigator, (Bowditch 2002).
Thomas J. Cutler, Dutton's Nautical Navigation, 15th Edition, Naval Institute Press (2004).
John Karl, Celestial Navigation in the GPS Age, Paradise Cay Publications (2007).
David Burch, Emergency Navigation, Second Edition, McGraw-Hill (2008).
David Owen Bell, The Celestial Navigation Mystery: Solved, Landfall Navigation (1999).
Hewitt Schlereth, Celestial Navigation in a Nutshell, Sheridan House (2000).
James A. Van Allen, An Analytical Solution Of The Two Star Sight Problem Of Celestial Navigation, Navigation 28 (1), pp. 40-43 (1981).
http://eclipse.gsfc.nasa.gov/SEhelp/deltatpoly2004.html
http://simbad.u-strasbg.fr/
http://www.backbearing.com/

and from Great Circle Mapper FAQ
"There isn't complete agreement on whether latitude or longitude comes first (though usually it's latitude) and it saves confusion to make N/S and E/W explicit.
Besides that confusion, the source data has surprisingly little consistency in the sign conventions for the hemispheres. One might expect negative latitudes to be south of the equator and negative longitudes to be west of the prime meridian. However, an early dump of the FAA data had the sign of the longitude reversed so most of the airports it lists have positive longitudes. (Not all, though. US territories are listed, and GUM, for example, is in the eastern hemisphere, as are a few airports in the far reaches of Alaska's Aleutian Islands.) An even stranger convention was found in the first file from which I distilled the IATA and ICAO data. While longitudes were normal enough, latitudes were relative to the south pole, so the equator was at 90 degrees, not zero, and the north pole was at 180! (This is called a false northing.)"

FINALLY from page 24 of the HP-65 Navigation Pac
"Li = initial latitude (N. positive: S. negative)"
"dj = initial longitude (W. positive: S. negative)"
with respect to program NAV 1-08a Dead Reckoning.

BEST!
SlideRule

[Geoff Quickfall]

Yes, unlike recessive and dominant genes there appears to be no acccepted standard. My 71b, prog use the input

1. Naabb.c
2. Saabb.c
3. Eaabb.c
4. Waabb.c
   

The programs then test for the alpha character N, S, E and W and assign the sign automatically with North and West +ve and South and East -ve. My other calculators, for ease of input require the signs.

Although this is not a convention, it is how the formula I have used, as published in the FAA documentation accept the differentiation. Of course this is using the equator as 0 latitude and the longitude increasing to 180 leaving Greenwich heading west until the dateline the decreasing heading west back to 0 at Greenwich.

Here is how a ships officer would assign the sign:

Great circle sailing

So I think it is how you are instructed to use the formula and that is based on the formula and its internal conventio/construction. The formula I first used was out of the HP 25 handbook. Subsequently I have used this formula and found the same in aviation handbooks.

Interestingly, the on board navigation computer (FMC) when heading west from Vancouver, over the dateline displays the dateline as W180 00.0. And when heading east from Asia displays the dateline as E180 00.0.

Geoff

P.s. Sliderule: should second yellow line be (W. positive: E. negative) and by the way, this is the formulae convention HP has used throughout its calculator manuals, not just the 67.

[SlideRule]

(05-10-2017 05:09 PM)Geoff Quickfall Wrote:  P.s. Sliderule: should second yellow line be (W. positive: E. negative)

Yes, I noticed this as well but chose to "quote" the manual for the HP 65 Navigation Pac verbatim. Thanks for highlighting the same {but unstated by me} observation. Does anyone have a confirming errata/ addendum for this observation? I'm still searching my archives for same.

BEST!
SlideRule

[Matt Agajanian]

SlideRule, Geoff,

Thank you for your extensive explanations. I appreciate them. I wonder if it just boils down to its final point of calculation--the HP-65's computational specifics.

[Geoff Quickfall]

In a nutshell, yes. Pick your convention and tailor the formula to reflect that.

I use the HP formula therefore N and W are +ve; S and E are -ve.

Coincidentally my photometrics, mapping and surveys and all my navigation courses have been based on the above convention as are my HP manuals.

Cheers, Geoff

[Matt Agajanian]

As always, thanks!