Real Navigation with SH4 - Page 6

kv29 · 06-14-07, 12:09 PM

ins´t local noon time = clock time - (SS - SR times / 2)?

Minimax · 06-14-07, 12:21 PM

thats one part, I will analyse...

don1reed · 06-14-07, 03:42 PM

SR and SS / 2 = Noon for the center of the Time Zone, i.e., 0-15-30-45-60-75-90-105-120-135-150-165-180, not your Long. You then must add or subtract the difference in time for when the Sun Bearing is due N or S of your position, (4 min = 1°).

Example:

Sun Almanac computed noon = 1202 for time zone 180E.

The Sun at my location crossed meridian at 1207.

1207 - 1202 = 5min. each min = 15' or .25°, then:

179° 60' E -1° 15' = 178° 45' E, my computed LONG.

-...-

Using the Observation scope is problematic due to the bobbing effect and not being able to bring the body down to the horizon.

What is needed is the capability to have a split image on the Observation scope that works for the celestial bodies without having to use the "L" key to lock it in on a ship...and a way to measure the vertical angle.

I'm not a modder, but thats whats needed to simulate a sextant.

06-15-07, 06:50 AM

I've been following this topic with great interest and I agree that having the OBS scope modded to act like a sextant would be very cool. Might be an idea to ask l3th4l or CaptainCox to take a look into this as they have produced some decent scope mods so far.

I'm new to this navigation malarchy, inspired really by my desire to calculate manual LAT/LONG position readings and comparing them with GPS data whilst crossing Greenland in august. I'm reading "Longitude" at the moment and would like to test my understanding of the theory by using SHIV (or 3).

That said, i'm having difficulty following some of the posts here as I lack some of the basics, could some kind soul list what would be required for us "newbs" to enter into this manual navigation realm ? Its been mentioned we'd need an almanac with pre 1952 dates, a sextant and a means of knowing both local and some refrence time (e.g. GMT). Is this all or am I grossly underestimating things ?

don1reed · 06-15-07, 07:06 AM

Howdy, UG. Good to see ya.

Be glad to help if we can.

I guess it stands to reason that one of the scopes could also second as a sextant. The only reason I chose the Observation scope is due to it's ~90° range of vertical motion. After all, if we use it to ascertain range of targets, then, there's no reason why it wouldn't work for measuing the altitudes of heavenly bodies.

In real life sextants are very delicate and accurate to within 0.1 m.o.a. I doubt we could ever attain that kind of accuracy with the sim, but one never knows. I've put a REQ up here asking the brilliant modders to have a look...never took hold. I guess not enough interest overall from them to have a serious look.

06-15-07, 07:12 AM

Hi Don,

Hope you don't mind but I took the liberty to ask if it would be possible to mod the OBS scope in the Better Scopes topic: http://www.subsim.com/radioroom/show...d=1#post567340

I also quoted your findings...hopefully they might be able to provide some input. I'm sure the cameras.dat file could be modded to give us the necessary scope movement. The it would *only* be a question of scaling the OBS marks to measure degrees given some knowledge of the celestial sphere in SHIV. At least thats what i think....

don1reed · 06-15-07, 07:15 AM

Tnx Mav and minimax, those websites are very useful.

don1reed · 06-15-07, 07:44 AM

@ Uber.

Great Job

Don't know why we didn't think of doing it earlier...another set of eyes and another brain.

Minimax · 06-15-07, 09:42 AM

@Uber Gruber
very good idea!

next test:

7.Jan'42
my position: 27°55'N 175°00'E (hold it all the day)
starting position (= base time) 179°E = UT1+12

SR:
upper edge: 07:03
red light off: 07:15
lower edge: 07:27

sun at 180° 12:31

SS:
lower edge: 17:23
red light on: 17:36
upper edge: 17:47 (uncertain)

sun culmination:
upper SR + (upper SS - upper SR)/2 = 12:25
red light SR + (red light SS - red light SR)/2 = 12:25,5
upper SR + (upper SS - upper SR)/2 = 12:23

sun culmination as shown in "Nautic Tools": 12:26

my conclusion:
although SS and SR aren't correct,
thats realy god for appoint longitude by using the red light.

Butr there was no chance to get an angle at culmination.

Minimax · 06-15-07, 10:16 AM

next test:

shot of Solaris (I've no reality - practice in shooting stars

)

my position: 27°45'N 175°00'E
7. Jan 42 20:05 basetime = 08:05 GMT

Solaris is 27°30' above chine (it's very hard to read)

but it should be 20°28' - am I right?

06-15-07, 12:20 PM

It's a hughe factor what Angular Angle you have for the camara you are spotting through i would think...

Try measuring the same star at the same time just standing on the bridge.

This is another thing to CONSIDER when putting all this together - we need a uniform camaras.dat file for it...

As a curiosum - my best experience with zoom, angular angle etc. is zoom at 1, angular angle at 60 - after that we need to "make" or adapt a sextant image to this. I have done that and printed the sextant on a transparent overlay to hold up against the screen. Works decent enough. The image i have used is the sextant image from Vanjast's mod for SH-III

Minimax · 06-15-07, 02:28 PM

Do you have a screenshot of this?

And how do you get the sextant only on the external view?
(moveable?)

06-15-07, 03:51 PM

the sextant is not on my screen. Its physicaly printed on a transparent paper. I then stick it up on the screen with my greasy fingers. So i can actualy have it both on the bridge and inside the sub

Minimax · 06-15-07, 03:53 PM

thats great! It IS movable

06-18-07, 01:35 AM

Hmmmmm - if we give the observation scope 50 deg of Angular Angle (Field of View in degrees) then you should have your sextant - being able to measure 100 deg. with two looks

What you would then need is a different optical divider set that gives divitions like a sextant instead of a scope.

This would though render the scope useless as a scope...

06-14-07, 12:21 PM	#77
Minimax Seaman Join Date: May 2007 Posts: 34 Downloads: 0 Uploads: 0	thats one part, I will analyse... __________________ if you think, my English is bad: try my French!

06-14-07, 03:42 PM	#78
don1reed Ace of the Deep Join Date: Dec 2004 Location: Valhalla: Silent Generation Posts: 1,149 Downloads: 910 Uploads: 0	SR and SS / 2 = Noon for the center of the Time Zone, i.e., 0-15-30-45-60-75-90-105-120-135-150-165-180, not your Long. You then must add or subtract the difference in time for when the Sun Bearing is due N or S of your position, (4 min = 1°). Example: Sun Almanac computed noon = 1202 for time zone 180E. The Sun at my location crossed meridian at 1207. 1207 - 1202 = 5min. each min = 15' or .25°, then: 179° 60' E -1° 15' = 178° 45' E, my computed LONG. -...- Using the Observation scope is problematic due to the bobbing effect and not being able to bring the body down to the horizon. What is needed is the capability to have a split image on the Observation scope that works for the celestial bodies without having to use the "L" key to lock it in on a ship...and a way to measure the vertical angle. I'm not a modder, but thats whats needed to simulate a sextant. __________________ During times of universal deceit, telling the truth becomes a revolutionary act. ~ George Orwell

06-15-07, 07:06 AM	#80
don1reed Ace of the Deep Join Date: Dec 2004 Location: Valhalla: Silent Generation Posts: 1,149 Downloads: 910 Uploads: 0	Howdy, UG. Good to see ya. Be glad to help if we can. I guess it stands to reason that one of the scopes could also second as a sextant. The only reason I chose the Observation scope is due to it's ~90° range of vertical motion. After all, if we use it to ascertain range of targets, then, there's no reason why it wouldn't work for measuing the altitudes of heavenly bodies. In real life sextants are very delicate and accurate to within 0.1 m.o.a. I doubt we could ever attain that kind of accuracy with the sim, but one never knows. I've put a REQ up here asking the brilliant modders to have a look...never took hold. I guess not enough interest overall from them to have a serious look. __________________ During times of universal deceit, telling the truth becomes a revolutionary act. ~ George Orwell

06-15-07, 07:15 AM	#82
don1reed Ace of the Deep Join Date: Dec 2004 Location: Valhalla: Silent Generation Posts: 1,149 Downloads: 910 Uploads: 0	Tnx Mav and minimax, those websites are very useful. __________________ During times of universal deceit, telling the truth becomes a revolutionary act. ~ George Orwell

06-15-07, 07:44 AM	#83
don1reed Ace of the Deep Join Date: Dec 2004 Location: Valhalla: Silent Generation Posts: 1,149 Downloads: 910 Uploads: 0	@ Uber. Great Job Don't know why we didn't think of doing it earlier...another set of eyes and another brain. __________________ During times of universal deceit, telling the truth becomes a revolutionary act. ~ George Orwell

06-14-07, 12:09 PM	#76
kv29 Watch Officer Join Date: May 2007 Location: Buenos Aires Posts: 342 Downloads: 2 Uploads: 0	ins´t local noon time = clock time - (SS - SR times / 2)?

06-15-07, 06:50 AM	#79
Uber Gruber Stowaway Posts: n/a Downloads: Uploads:	I've been following this topic with great interest and I agree that having the OBS scope modded to act like a sextant would be very cool. Might be an idea to ask l3th4l or CaptainCox to take a look into this as they have produced some decent scope mods so far. I'm new to this navigation malarchy, inspired really by my desire to calculate manual LAT/LONG position readings and comparing them with GPS data whilst crossing Greenland in august. I'm reading "Longitude" at the moment and would like to test my understanding of the theory by using SHIV (or 3). That said, i'm having difficulty following some of the posts here as I lack some of the basics, could some kind soul list what would be required for us "newbs" to enter into this manual navigation realm ? Its been mentioned we'd need an almanac with pre 1952 dates, a sextant and a means of knowing both local and some refrence time (e.g. GMT). Is this all or am I grossly underestimating things ?

06-15-07, 07:12 AM	#81
Uber Gruber Stowaway Posts: n/a Downloads: Uploads:	Hi Don, Hope you don't mind but I took the liberty to ask if it would be possible to mod the OBS scope in the Better Scopes topic: http://www.subsim.com/radioroom/show...d=1#post567340 I also quoted your findings...hopefully they might be able to provide some input. I'm sure the cameras.dat file could be modded to give us the necessary scope movement. The it would only be a question of scaling the OBS marks to measure degrees given some knowledge of the celestial sphere in SHIV. At least thats what i think....

06-15-07, 09:42 AM	#84
Minimax Seaman Join Date: May 2007 Posts: 34 Downloads: 0 Uploads: 0	@Uber Gruber very good idea! next test: 7.Jan'42 my position: 27°55'N 175°00'E (hold it all the day) starting position (= base time) 179°E = UT1+12 SR: upper edge: 07:03 red light off: 07:15 lower edge: 07:27 sun at 180° 12:31 SS: lower edge: 17:23 red light on: 17:36 upper edge: 17:47 (uncertain) sun culmination: upper SR + (upper SS - upper SR)/2 = 12:25 red light SR + (red light SS - red light SR)/2 = 12:25,5 upper SR + (upper SS - upper SR)/2 = 12:23 sun culmination as shown in "Nautic Tools": 12:26 my conclusion: although SS and SR aren't correct, thats realy god for appoint longitude by using the red light. Butr there was no chance to get an angle at culmination. __________________ if you think, my English is bad: try my French!

06-15-07, 10:16 AM	#85
Minimax Seaman Join Date: May 2007 Posts: 34 Downloads: 0 Uploads: 0	next test: shot of Solaris (I've no reality - practice in shooting stars ) my position: 27°45'N 175°00'E 7. Jan 42 20:05 basetime = 08:05 GMT Solaris is 27°30' above chine (it's very hard to read) but it should be 20°28' - am I right? __________________ if you think, my English is bad: try my French!

06-15-07, 12:20 PM	#86
Mav87th Stowaway Posts: n/a Downloads: Uploads:	It's a hughe factor what Angular Angle you have for the camara you are spotting through i would think... Try measuring the same star at the same time just standing on the bridge. This is another thing to CONSIDER when putting all this together - we need a uniform camaras.dat file for it... As a curiosum - my best experience with zoom, angular angle etc. is zoom at 1, angular angle at 60 - after that we need to "make" or adapt a sextant image to this. I have done that and printed the sextant on a transparent overlay to hold up against the screen. Works decent enough. The image i have used is the sextant image from Vanjast's mod for SH-III

06-15-07, 02:28 PM	#87
Minimax Seaman Join Date: May 2007 Posts: 34 Downloads: 0 Uploads: 0	Do you have a screenshot of this? And how do you get the sextant only on the external view? (moveable?) __________________ if you think, my English is bad: try my French!

06-15-07, 03:51 PM	#88
Mav87th Stowaway Posts: n/a Downloads: Uploads:	the sextant is not on my screen. Its physicaly printed on a transparent paper. I then stick it up on the screen with my greasy fingers. So i can actualy have it both on the bridge and inside the sub

06-15-07, 03:53 PM	#89
Minimax Seaman Join Date: May 2007 Posts: 34 Downloads: 0 Uploads: 0	thats great! It IS movable __________________ if you think, my English is bad: try my French!

06-18-07, 01:35 AM	#90
Mav87th Stowaway Posts: n/a Downloads: Uploads:	Hmmmmm - if we give the observation scope 50 deg of Angular Angle (Field of View in degrees) then you should have your sextant - being able to measure 100 deg. with two looks What you would then need is a different optical divider set that gives divitions like a sextant instead of a scope. This would though render the scope useless as a scope...