Celestial Navigation Plugin Redux

[stelian]

Originally Posted by rgleason

Sean's responses quoted:

Yes, well the find body is only approximate. It doesn't perform the atmospheric corrections and height of eye and other calculations, this is why they don't align perfectly. When calculations are performed the other way around for real sights, all the corrections are performed.

I've already said this in #554 . I guess this thread is becoming too dense...

[P_Dub]

Something is wrong with this one, it does not work properly. Will do more test this morning.

[P_Dub]

It works OK once you have enter an approximate DR say -12 (for 12 S) and -126 (for 126 W), the position calculated is very close to the calculated one.
12-26.3 S, 125-31.1 W versus the hand one 12-26.8 S, 125-30.8 W
The difference then is little in practice in open ocean.
So you are now on the good road to success.
Bye

[rgleason]

What would it take to make the FIND function calculate the eye level and other parameters, so that it follows the calculations of taking a real sight exactly?
It would enable use to check things better.
Also the plugin would be more intuitive without as many but this... and the manual would not have to explain anything further!
I think the expectation is that FIND is calculated similar to a SIGHT!

---------------------------------------
Sean's responses quoted:

The crossings of the sights seem closer, but they're still 54nm away from the VDR file I made for 42.35 -71.1 Quote:
Yes, well the find body is only approximate. It doesn't perform the atmospheric corrections and height of eye and other calculations, this is why they don't align perfectly. When calculations are performed the other way around for real sights, all the corrections are performed.
Quote:
It might be nice to improve the find body to perform all the corrections in reverse, but it does explain why other people have verified the plugin does work for real sights.

---------------------------
Stelian's #554 http://www.cruisersforum.com/forums/...ml#post2496419
Sorry, sometimes I need to reconnect things..

What would happen if I set the parameters to 0 height etc.? while using FIND?
--------

[rgleason]

Maybe its as simple as under FIND including a

[Checkbox] Include parameter calculations

[rgleason]

By setting Parameters - Eye Height=0

The sights move closer together, so something is being done with the Eye Height parameter, of course. By setting all the Eye Heights=0 and using FIND to get the altitude again, the FIX becomes 18nm. (closer)

What are the default Parameter values that FIND should use to have accurate Sights?
This should be easy. I think they are standard default settings for each FIND.
PARAMETER
Eye Height=0
Temperature=? -What would be the default for 0 adjustment?
Pressure=? -What would be the default for 0 adjustment?
Index Error=0

Maybe FIND has to be disconnected from the Sight Parameter Settings under the PARAMETERS TAB and just use these typical default settings that result in NO correction being applied for the FIND resultant altitude/azimuth. So once that "uncorrected" altitude/azimuth is entered from FIND into the SIGHT measurement value. THEN and only then are the CORRECTIONS from the PARAMETERS TAB applied!

I think this can be fixed. FIND should indicate the correct altitude/azimuth angle to enter into a SIGHT so that the resultant SIGHT with the PARAMETER TAB corrections applied, shows in the right location and the FIX works properly.

FIND should not use any of the PARAMETERS TAB values (corrections) to calculate or they should all be set to default to 0, I think.

[rgleason]

It looks to me like FindBodyDialog.cpp doesn't do anything but find the altitude/azimuth.

--So when that value is entered into the sight, what is wrong?

--Ah ah, from the Table angle, we have to actually make the Corrections from the PARAMETERS TAB and then use that Corrected angle to enter into the sight.

--So I was wrong, the Altitude or Azimuth angle that FIND looks up in the tables has to be ADJUSTED to the Angle that a NAVIGATOR taking sights would see, by actually making the Corrections in the Parameters Tab. So it is just a little more math and perhaps another "Corrected measurement" Line that can be copied in the FIND Dialogue.

So FindBodyDialog.cpp needs some lines that will calculate the Corrections required for the PARAMETERS TAB and show a line for "Corrected angle" under Altitude and Azimuth.

Or have a choice to [X] Correct for Parameters

Line 300 - 303 off SightDialog.cpp Calculations
Under void SightDialog::Recompute()
m_tEyeHeight->GetValue().ToDouble(&m_Sight.m_EyeHeight);
m_Sight.m_Temperature = m_sTemperature->GetValue();
m_Sight.m_Pressure = m_sPressure->GetValue();
m_tIndexError->GetValue().ToDouble(&m_Sight.m_IndexError);

[rgleason]

Is this version ready & tested enough to replace the version on the Downloads?
Personally, I think it's much better, and we have Sean and Stelian to thank for the improvements.

[rgleason]

Kubek, would you mind posting or attaching a file with the sights you used and the actual boat position? So I can check and see for myself?

Thanks

Originally Posted by kubek

Hi,

I can confirm that "Beta celestial_navigation_pi-2.2.003-ov4.-win32" version is accurate.
I put my 5 physical sights from summer voyage Canaries - Cabo Verde and accuracy is less then 2 NM, only one sight have near 3 NM. So plugin works perfect and those errors are like human measure error.

Great work!

Thanks again,

Kubek

[rgleason]

Saw Sean today and we discussed Cel Nav PI. In particular the FIND menu. He advises that that was his idea so that the stars could be found, and reiterated that it does not do the Parameter Tab corrections. He explained that to make FIND altitude and azimuth work from the established Boat Position, the formulas would have to be reversed from those that are used for Sights.

[kubek]

Originally Posted by rgleason

Kubek, would you mind posting or attaching a file with the sights you used and the actual boat position? So I can check and see for myself?

Thanks

Hi,

Below my sights that I have taken:
Astro01: Sun LL, 2.07.2017 09:33:32 UT, 39°48.8', index error -1.5', Height of eye 2.0m | 27°42,1'N 017°54,8'W
Astro02: Sun LL, 2.07.2017 15:36:20 UT, 58°03.2', index error -1.5', Height of eye 2.0m | 27°05,1'N 018°12,5'W
Astro03: Sun LL, 2.07.2017 18:44:55 UT, 16°45.0', index error -1.5', Height of eye 2.0m | 26°50,5'N 018°14,0'W
Astro04: Mer Pass, 3.07.2017 13:19:52 UT, 86°49.9', index error -1.5', Height of eye 2.0m | 25°51,9'N 018°41,2'W
Astro05: Sun LL, 3.07.2017 16:24:04 UT, 47°54.0', index error -1.5', Height of eye 2.0m | 25°39,9'N 018°50,5'W
Astro06: Sun LL, 3.07.2017 18:42:34 UT, 17°30.0', index error -1.5', Height of eye 2.0m | 25°32,0'N 018°57,6'W
Astro07: Sun LL, 4.07.2017 10:29:48 UT, 50°02.8', index error -1.5', Height of eye 2.0m | 24°42,7'N 019°58,0'W
Astro08: Mer Pass, 4.07.2017 13:25:10 UT, 88°10.0', index error -1.5', Height of eye 2.0m | 24°27,6'N 020°07,6'W
Astro09: Sun LL, 4.07.2017 18:11:11 UT, 25°11.8', index error -1.5', Height of eye 2.0m | 24°01,7'N 020°25,1'W
Astro10: Sun LL, 5.07.2017 10:10:16 UT, 43°49.8', index error -1.5', Height of eye 2.0m | 22°40,6'N 021°31,5'W
Astro11: Sun LL, 5.07.2017 14:09:27 UT, 80°56.2', index error -1.5', Height of eye 2.0m | 22°14,5'N 021°38,4'W
Astro12: Sun LL, 6.07.2017 12:20:22 UT, 72°00.2', index error -1.5', Height of eye 2.0m | 20°33,0'N 022°53,4'W
Astro13: Mer Pass, 6.07.2017 13:37:00 UT, 87°40.0', index error -1.5', Height of eye 2.0m | 20°29,0'N 023°00,0'W
Astro14: Moon UL, 6.07.2017 19:49:38 UT, 19°50.3', index error -1.5', Height of eye 2.0m | 19°56,0'N 023°09,9'W
Astro15: Vega, 6.07.2017 20:55:33 UT, 32°34.0', index error -1.5', Height of eye 2.0m | 19°49,6'N 023°11,0'W
Astro16: Sun LL, 7.07.2017 10:54:01 UT, 51°03.2', index error -1.5', Height of eye 2.0m | 18°25,5'N 023°32,2'W
Astro17: Mer Pass, 7.07.2017 13:38:30 UT, 85°27.0', index error -1.5', Height of eye 2.0m | 18°10,7'N 023°37,0'W

Kubek

[rgleason]

Thanks Kubek, Very much. If it works as it did for you, then I guess it's ready to go to the Downloads page.

[rgleason]

Here are my results using Kubek's 17 sights.

Please take the ".doc" off of the three files.

17-sights.jpg Screenshot

Astro1-17.gpx wapoints for Long/Lat

17-sights.xml.doc XML file for sights (take the "17-" off and the ".doc" off and put it in your programdata/opencpn/plugins/celestial_navigation/ folder to see how they appear in Celestial_Navigation_pi.

17-Sights-Kubek.txt.doc Kubec's original sights.

I'm not finding a strong correlation, but perhaps I made some mistakes. I do know that 3 of the mercury sights were not showing and wonder why.

[rgleason]

Using the first Example for 4 sights in the Cel-Nav Manual there is a very good fix.

[kubek]

Hi,

Here you can see my all 17 sights in OpenCPN. The worst accuracy is in Astro07 near 5 NM, rest accuracy is 1-3 NM (which is very good from ocean passage perspective).

Kubek