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Distances and bearings between points
08-16-2014, 08:18 AM
Post: #1
Distances and bearings between points
I am looking for hp prime program(s) / solution(s) to help me work with distances and bearings between points, using the Vincenty method. This is just for my personal interest, and I would appreciate help locating resources that are useful on the hp prime, if any happen to exist. Thanks!

-Dale-
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10-07-2016, 10:58 AM
Post: #2
RE: Distances and bearings between points
(08-16-2014 08:18 AM)DrD Wrote:  I am looking for hp prime program(s) / solution(s) to help me work with distances and bearings between points, using the Vincenty method. This is just for my personal interest, and I would appreciate help locating resources that are useful on the hp prime, if any happen to exist. Thanks!

-Dale-

I have recently been trying to code that on the HP Prime, but it's not yet returning correct results.

It would be really helpful if someone had a step-by-step worked example so that I could pinpoint the error(s) in my code.

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10-07-2016, 12:43 PM
Post: #3
RE: Distances and bearings between points
Not specifically addressing the question, and you may have already seen this site, but it may be useful: http://williams.best.vwh.net/

-Dale-
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10-17-2016, 10:31 PM (This post was last modified: 10-23-2016 06:35 PM by StephenG1CMZ.)
Post: #4
RE: Distances and bearings between points
I have uploaded two routines for LatLong to Distance to my Geodesy program in the software library.
One, the Haversine method.
Two, a simplification of the ellipsoidal Vincenty formula for a spherical Earth.

My implementation of the ellipsoidal Vincenty formula needs more work - results are currently less accurate than using the spherical calculations.
Update: V0 .3 now includes Vincenty.

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10-23-2016, 06:33 PM (This post was last modified: 10-23-2016 06:53 PM by StephenG1CMZ.)
Post: #5
RE: Distances and bearings between points
My geodesy program now implements lat-long-to-distance calculations.
Spherical calculations use Haversine. Ellipsoidal calculations use Vincenty 1975.

Hope you find this useful. If you are still using V0.1 or V0.2, please don't - please delete and upgrade.

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11-23-2016, 10:03 PM
Post: #6
RE: Distances and bearings between points
My V0.3 implementation of the Inverse Vincenty algorithm had a typo - corrected by V0.32.

I have also made an attempt at the Direct Vincenty algorithm, but my implementation of that is not yet correct.

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11-23-2016, 11:08 PM
Post: #7
RE: Distances and bearings between points
I think there were worked out examples for antenna pointing applications in the ARRL handbook, or the ARRL Antenna book, maybe even both. There was also an article in a Ham Radio Magazine edition that had details, (with a program example) for antenna pointing. You can probably find that on the web still.

For navigation purposes, given the current state of the art of electronic chart plotters, and GPS technology, it hardly seems worthwhile to calculate such things anymore. Still, it is fun to create the programs!

Then there are the GPS messages, which you might be able decode from a personal GPS handheld such as the Garmin Oregon, or newer, models. At least I had fun doing that. I might be a little on the crazy side, since I also had a vector scope radio transmitter locator that used GPS messages for location purposes. I decoded the GPS messages and kept the location info in a spreadsheet of known interference sites to a natural gas telemetry system used by our local utility. (Retired from that job now, but it was a lot of fun!)

Another thing that is fun to work with is marine AIS. If the hp prime USB by wire evolves sufficiently, you might even be able to take output from a Marine VHF radio and decode the AIS messages, to track commercial vessels within radio range. Even without an AIS radio system, you could still make a program to decode AIS messages.

These things were all a spin off from my interest in similar activities such as you are working with now.

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11-24-2016, 10:26 PM
Post: #8
RE: Distances and bearings between points
Back when I was at the Nautical College, I realized that when using rhumb line for calculation we were using a spheroidal model, but while using great circle a sphere was used. I asked my teacher about this, and then he stared at me as if he never noticed this thing before. He was like Eerrrr... ummmm... etc. A week or so later (this happened before the Wikipedia times)he came back with a paper with the vincenty method, and a face telling "you are not going to pass my subject this year". And in fact I didn't passed the subject that year, although I was quite competent in doing all kind of nautical calculations. I even had programmed my 48sx at that time.
So I can tell that I have a bittersweet memory of mr Vincenty...
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11-25-2016, 04:40 PM
Post: #9
RE: Distances and bearings between points
Dale,

That work sounds very interesting.

I have previously developed client software for modem applications - back in the days when modems were real boxes doing dial-up. And a radio telemetry protocol designed for aerospace... Vehicles.

So the thought that I might one day be using these distance calculations together with GPS or AIS decoding has crossed my mind - especially since I live within VHF range of the coast.

When I first started to look into the HP Prime for on-Android/on-calculator compiling, I was thinking one might be able to plug a GPS/AIS into a datastreamer into a HP Prime...but I believe the datastreamer is not that flexible.

As for using existing navigational devices - I find it astonishing that my Google Maps is so good at drawing maps, but abysmal at displaying your latitude and longitude - and distance from a repeater.

(If anyone needs software to their custom requirements - mail me).

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