Real Navigation Mod - Page 5

don1reed · 06-25-07, 08:21 AM

You have a very valid arguement.

Another test we must make is to see if the UT and Local clocks in SH3 change when we precisely cross TimeZone boundary. Does the clock change at the middle of the TZ or does it change at the boundaries, i.e.,

7° 30' W......000°......7° 30' E......015°......
|..................|.................|

here......or....here?

Another thing to note that IRL SR and SS occur when the UL is flush with sea level, see pic below. However, the Devs have made SR/SS at the time the Sun is already half out of the water. (When red light goes on/off).

So, a few adjustments must be made to get the navigational consistancy we need.

06-25-07, 09:57 AM

Quote:

Originally Posted by don1reed

You have a very valid arguement.
So, a few adjustments must be made to get the navigational consistancy we need.

I must say that all this is nice fun and interesting learning! I was thinking about problem but gave it up after reading Vans threads. It might be possible that if now I'm at 64°N that real SR/SS might take a lot longer. If I get it right I should measure with sextant those 12° and just wait till only that portion of sun "is sticking out of the water"? I'll try to check it all later. Just stick for some time near Reykjavik for the readings as I still have 2 eels aboard

ichso · 06-25-07, 12:06 PM

It would be really nice to get it working properly. It is fun playing out the navigational efforts but if one cannot estimate the longitudes good enough it's a little pointless in the long run.
Thanks for all the work and research you've invested so far. I hadn't time to play since a few days now. But I will go on testing in a few days so that we come to either a conclusion how the longitudes can be measured precisely or at least that it can't be done to a satisfiying amount.

In that case it might be better to just turn the mod off again :/

don1reed · 06-26-07, 09:15 AM

"Timing is Everything", its been said, but, no where more important than when used with Navigation.

Alright...

Here's two pics which may shed a little light on our problem.

1st pic is of 6.9.1939 Uboat posit AP 54° N, 008° E. Zone Description (A -1)

Note that the upper time is called "LOCAL TIME" (06:43)..and the lower time in the white box (05:43) is not labeled. I presume everyone thought the time in the white background box was UT (GMT). Right?

Here have a look...

...Now...

Using StarCalc and a real life navigation program, "Navigator" to determine SR at my location, check out the UT times compared to the Times in zone Alpha -1:

This shows me that the time designated "Local Time" in the Sim is one (1) hour off, and the time everyone thought was UT is also aflicted with that 1 hour discrepency.

Time ...forgive the pun...for an adjustment.

Edit: The only thing correct about the two times in the first pic is that there is a one hour difference between UT and Local time at my geo coordinates. So, the time in the lower white box is in fact the real LOCAL TIME, I must then resort to my "Local Time to GMT conversion chart", as I've always done.

Same ole, same ole...

...anyway...here's how my SR unfolded:

Using Sun Almanac that came with RealNav

Interpolate:

60-N
50-N There are 10° difference I'm about 54°N 4/10. There are 17 min. difference between the SR times for the two Latitudes.
4/10 x 17 = 0

48, subtracted from the SR time for 50N 5:21 - 0:6:48 = 5:14:11.

SR occurred at 05:43:06 (local) - 5:14:11 (local) = 0:28:55 / 4 = 7° 13'.

Middle of my time zone (15° E) - 7° 13' = 7° 47' E (my current longitude)

ichso · 06-26-07, 10:15 AM

Hey don, that is some very valuable information!

I'm gonna try that this evening.

One thing about your SR time there: How did you measure exactly this 05:43h ? Your still on redlight and the sun is not to be seen on the above screenshot yet.
I used to wait until just a glimps of the sun was seen for the SR time, that was also the same moment as the redlight gets turned off.

don1reed · 06-26-07, 11:47 AM

Quote:

How did you measure exactly this 05:43h ?

I got that time from "StarCalc" as the SR for assumed position (AP) 54° N, 008° E. That time was also in sync with my Navigator pgm as SR from my posit.

I've GWX and NYGM on my HD and this time I was using GWX which doesn't show the sun very well through the scopes or binocs. When on the bridge the sun shows up too well and very bright where I cannot see it's outline at all...needs sun filters like real sextant.

06-26-07, 12:20 PM

Quote:

Originally Posted by don1reed

Quote:

How did you measure exactly this 05:43h ?

I got that time from "StarCalc" as the SR for assumed position (AP) 54° N, 008° E. That time was also in sync with my Navigator pgm as SR from my posit.

I've GWX and NYGM on my HD and this time I was using GWX which doesn't show the sun very well through the scopes or binocs. When on the bridge the sun shows up too well and very bright where I cannot see it's outline at all...needs sun filters like real sextant.

I'll go through what you posted, sounds interesting but I'm losing my nerves quickly. Today I've tried to navigate from Lorient. Flat sea and even before going NW i was way off. 1-2 hour corrections didn't change anything and it was like 180-181-180°... so I'm pissed because I can do everything precisely and it doesn't matter at all. Damn helmsman. Need to fix him (it).

ichso · 06-26-07, 03:58 PM

Weird or not ?
My current patrol:
Jan 1st, 1941. Latitude at midnight: 40°.
SR/SS Almanac from the mod says that I should get a SR at 7:22 local time for 40°N and 7:58 at 50°N.
By taking speed (10.5kn) and course (000°) into account, my position at SR would be at lat. 41,5°N.

Difference for SR times from 50°N to 40°N: 36min
1.5/10 * 36 = 05:24m.
So SR at 41,50° would be at 7:27:24.
7:58:00 - 7:27:24 = 0:30:36.
0:30:36 / 1.5 = 20.333...
which is my current longitude.

Don't know if I forgot something. I didn't take into account that the changes of the time difference between local and GMT occur at the middle of the timezone.

ichso · 06-26-07, 05:13 PM

A new attempt 2 days later:
Lat: 47.5°N
So referring to the Van's Sun Almanac and interpolating between 40°N and 50°N again I should have seen the sun rise at 7:49 ( 8:49 loacl time at 15°W)
I tried to use the 'red light off' moment as my local SR time. this was at 9:10.

So I am 21 minutes behind the SR time for 15°W which would mean that I am ~5° farther west, so at ~20°W, which would meet my real longitude well (still being ~20.5°W).
I am not sure what to take as my referring point for the SR yet but the moment when red light turns off (= sun is to be seen by half of it's amount) fits well in this example. I will test this a little further tomorrow.

06-27-07, 08:34 AM

Quote:

Originally Posted by ichso

A new attempt 2 days later:
Lat: 47.5°N
So referring to the Van's Sun Almanac and interpolating between 40°N and 50°N again I should have seen the sun rise at 7:49 ( 8:49 loacl time at 15°W)
I tried to use the 'red light off' moment as my local SR time. this was at 9:10.

So I am 21 minutes behind the SR time for 15°W which would mean that I am ~5° farther west, so at ~20°W, which would meet my real longitude well (still being ~20.5°W).
I am not sure what to take as my referring point for the SR yet but the moment when red light turns off (= sun is to be seen by half of it's amount) fits well in this example. I will test this a little further tomorrow.

When you write 47.5*N is that 47*5'N or 47*50'N ? I assume the later

don1reed · 06-27-07, 08:47 AM

Its a hard grapple, I know. For me, the frustration level mounts daily...not good for an old fart with bad ticker

Something worth knowing:

1)Those SR/SS tables, both van's and IRL are in "LOCAL TIME". Its up to the mariner to compute UT (GMT).

2) Are we taking into account DayLight Time/DayLight Savings Time ?

3) I found out yesterday, while sailing NW in U.47 (AP 55° N, 7° 31' E), that the lower (white background) clock in SH3 dropped back one hour when the boat crossed meridian 7° 30' E, the boundary line between Prime Meridian 000° and 015° east.
edit: I'm going to replay this, just to make sure....

ichso · 06-27-07, 10:21 AM

Quote:

Originally Posted by Mav87th

When you write 47.5*N is that 47*5'N or 47*50'N ? I assume the later

Yes, sry, I meant 47°50'N

Quote:

Originally Posted by don1reed

1)Those SR/SS tables, both van's and IRL are in "LOCAL TIME". Its up to the mariner to compute UT (GMT).

Am I missing something again ? Van's SR/SS Almanac gives no Information about the longitude for any specific SR time. So it's the local time of what local point ? The only thing these SR/SS times can refer to is the GMT or am I wrong there ?
As I wrote in my previous post, the last time I tried to calculate my longitude I just used the time difference between the SR time from the almanac and the time my red light got turned off. At that moment I read the time from the upper clock, the one that pops up when you point with the cursor at the clock.
This difference was about ~1.3 hours (it was 9:10, the SR from the almanac read 7:49). And that calculated into my longitude ~20°W which was correct.

So I have the theory:

Quote:

Originally Posted by don1reed

3) I found out yesterday, while sailing NW in U.47 (AP 55° N, 7° 31' E), that the lower (white background) clock in SH3 dropped back one hour when the boat crossed meridian 7° 30' E, the boundary line between Prime Meridian 000° and 015° east.

That this doesn't matter for the SR/SS times you get from the almanac if you use the points of "redlight on/off". This seems to be exactly the time when the sun sticks half out of the water and maybe just that little time difference to local time to even out the effect that the local time switches not at 15°W/E, 30°W/E, ... but at 7°50'W/E, 22,5°50'W/E, ...

I will test that for some different longitudes this evening to see if it fits then too as it did yesterday.

don1reed · 06-27-07, 11:08 AM

Quote:

Am I missing something again ? Van's SR/SS Almanac gives no Information about the longitude for any specific SR time. So it's the local time of what local point ? The only thing these SR/SS times can refer to is the GMT or am I wrong there ?

Since the globe is, for navigational purposes, considered round, then its been established that the sun rises and sets at the same time in each of the 24 time zones.

When the sun is over my RL meridian, its RL noon in local time. When that occurs, it happens to be around 1800 GMT. There is a 6 hour difference between my RL local time and GMT for my RL location. Based on seasonal earth moving events (earth 23.5° tilt), SR/SS changes in timing perspective depending on your Latitude. Thats why the times are different day to day, month to month, etc.

If you take another look at the sun almanac you will notice that every SR and SS occurs at around the same time, i.e., SR in the morning and SS in the evening. If the table were based on GMT then the SR/SS times would all be different.

example:

Say you and I are stationary; I'm at 55-N 8-E and you're at 55-N 90W...

Based on the Almanac, the sun will rise and set at the exact same times...except your SR/SS will occur 6.53 hrs. later

As the earth rotates, the sun rises the same time locally as seen from the same latitude.

ichso · 06-27-07, 06:18 PM

The method I mentioned, using the moment when red light turns off as your SR time, seems to work well.
Just know your latitude as precise as possible. From Van's SR/SS almanac get the current local SR time by interpolating between the next bigger and next smaller given lat.value there.
Then just wait for the exact red-light-off-moment (minute wise) and get the difference from the above calculated SR time. This time difference is needed in hours, for example are 75 minutes of time difference to be used as 1.25 hours.
Multiply that number by 15 and that are the degrees your off from Greenwich.

I worked myself from the coast of Northern Africa up to Scotland and from there back to St.Nazaire with very good results of position calculations.

Had no ship encounter on the hole patrol though, nearly ran out of fuel before returning to base

06-28-07, 12:58 AM

We are basicaly working with 3 "times" here

BASE TIME: Gameclock (in SH-4 thats easy as there is only one! In SH-3 Don's findings shows that its NOT the one with white background)

GMT: Well that says it self. Van's SR/SS almanac is GMT times for SR/SS at 10 different lattitudes for each date all year in 1939 (Valid for all the war years)

LOCAL TIME: The "missing link". The time we need to convert the two others into in order to make our calculations. (Or if you want to skip that then convert all the SR/SS's into BASE TIME or vicaversa GMT's to BASE TIME)

Those convertions are what i ****ed up the most in the start, now im starting to get the hang of it. Just crossed the I-dateline in SH-4 after a great start from PEARL. First Sunset at around Lng 177E sat me 30nm off my real Lng. Im now waiting for the stars to shine through so i can take a fix on a couple of low stars. (I have found when using stars hanging low on the horizon to be most precise).

The fast and easy thing would be to shoot Polaris and take that reading for granted for Lat., witch is the way i do it when crossing the pond on the long jurneys. Then ocationally i take a 6 star fix and calculate the position from the star GP's etc etc. with Navigator. That takes me within 15nm most of the times (when im controling it)

Redlight time in SH-4 is DEFINETLY the correct SS/SR time - only thing missing is seconds in van's almanac to make it more precise, but i can get that from Navigator.

It's correct that you need to know your Lat. pretty precise, but if you sail a heading for an amount of time you are not going to end up to far from where you plan, unless you fastforward x1024 or more. In that case you have to sit "watch" at the helm and click it every time it strays from the course.

06-25-07, 08:21 AM	#61
don1reed Ace of the Deep Join Date: Dec 2004 Location: Valhalla: Silent Generation Posts: 1,149 Downloads: 910 Uploads: 0	You have a very valid arguement. Another test we must make is to see if the UT and Local clocks in SH3 change when we precisely cross TimeZone boundary. Does the clock change at the middle of the TZ or does it change at the boundaries, i.e., 7° 30' W......000°......7° 30' E......015°...... \|..................\|.................\| here......or....here? Another thing to note that IRL SR and SS occur when the UL is flush with sea level, see pic below. However, the Devs have made SR/SS at the time the Sun is already half out of the water. (When red light goes on/off). So, a few adjustments must be made to get the navigational consistancy we need. __________________ [SIGPIC][/SIGPIC] During times of universal deceit, telling the truth becomes a revolutionary act. ~ George Orwell Last edited by don1reed; 06-25-07 at 08:35 AM.

06-25-07, 12:06 PM	#63
ichso Ace of the Deep Join Date: Jul 2005 Location: Germany's oldest city alive Posts: 1,066 Downloads: 57 Uploads: 0	It would be really nice to get it working properly. It is fun playing out the navigational efforts but if one cannot estimate the longitudes good enough it's a little pointless in the long run. Thanks for all the work and research you've invested so far. I hadn't time to play since a few days now. But I will go on testing in a few days so that we come to either a conclusion how the longitudes can be measured precisely or at least that it can't be done to a satisfiying amount. In that case it might be better to just turn the mod off again :/ __________________ My Subskins: http://www.subsim.com/radioroom/showthread.php?t=164169

06-26-07, 09:15 AM	#64
don1reed Ace of the Deep Join Date: Dec 2004 Location: Valhalla: Silent Generation Posts: 1,149 Downloads: 910 Uploads: 0	"Timing is Everything", its been said, but, no where more important than when used with Navigation. Alright... Here's two pics which may shed a little light on our problem. 1st pic is of 6.9.1939 Uboat posit AP 54° N, 008° E. Zone Description (A -1) Note that the upper time is called "LOCAL TIME" (06:43)..and the lower time in the white box (05:43) is not labeled. I presume everyone thought the time in the white background box was UT (GMT). Right? Here have a look... ...Now... Using StarCalc and a real life navigation program, "Navigator" to determine SR at my location, check out the UT times compared to the Times in zone Alpha -1: This shows me that the time designated "Local Time" in the Sim is one (1) hour off, and the time everyone thought was UT is also aflicted with that 1 hour discrepency. Time ...forgive the pun...for an adjustment. Edit: The only thing correct about the two times in the first pic is that there is a one hour difference between UT and Local time at my geo coordinates. So, the time in the lower white box is in fact the real LOCAL TIME, I must then resort to my "Local Time to GMT conversion chart", as I've always done. Same ole, same ole... ...anyway...here's how my SR unfolded: Using Sun Almanac that came with RealNav Interpolate: 60-N 50-N There are 10° difference I'm about 54°N 4/10. There are 17 min. difference between the SR times for the two Latitudes. 4/10 x 17 = 048, subtracted from the SR time for 50N 5:21 - 0:6:48 = 5:14:11. SR occurred at 05:43:06 (local) - 5:14:11 (local) = 0:28:55 / 4 = 7° 13'. Middle of my time zone (15° E) - 7° 13' = 7° 47' E (my current longitude) __________________ [SIGPIC][/SIGPIC] During times of universal deceit, telling the truth becomes a revolutionary act. ~ George Orwell Last edited by don1reed; 06-26-07 at 10:00 AM.

06-26-07, 10:15 AM	#65
ichso Ace of the Deep Join Date: Jul 2005 Location: Germany's oldest city alive Posts: 1,066 Downloads: 57 Uploads: 0	Hey don, that is some very valuable information! I'm gonna try that this evening. One thing about your SR time there: How did you measure exactly this 05:43h ? Your still on redlight and the sun is not to be seen on the above screenshot yet. I used to wait until just a glimps of the sun was seen for the SR time, that was also the same moment as the redlight gets turned off. __________________ My Subskins: http://www.subsim.com/radioroom/showthread.php?t=164169

06-26-07, 03:58 PM	#68
ichso Ace of the Deep Join Date: Jul 2005 Location: Germany's oldest city alive Posts: 1,066 Downloads: 57 Uploads: 0	Weird or not ? My current patrol: Jan 1st, 1941. Latitude at midnight: 40°. SR/SS Almanac from the mod says that I should get a SR at 7:22 local time for 40°N and 7:58 at 50°N. By taking speed (10.5kn) and course (000°) into account, my position at SR would be at lat. 41,5°N. Difference for SR times from 50°N to 40°N: 36min 1.5/10 * 36 = 05:24m. So SR at 41,50° would be at 7:27:24. 7:58:00 - 7:27:24 = 0:30:36. 0:30:36 / 1.5 = 20.333... which is my current longitude. Don't know if I forgot something. I didn't take into account that the changes of the time difference between local and GMT occur at the middle of the timezone. __________________ My Subskins: http://www.subsim.com/radioroom/showthread.php?t=164169

06-26-07, 05:13 PM	#69
ichso Ace of the Deep Join Date: Jul 2005 Location: Germany's oldest city alive Posts: 1,066 Downloads: 57 Uploads: 0	A new attempt 2 days later: Lat: 47.5°N So referring to the Van's Sun Almanac and interpolating between 40°N and 50°N again I should have seen the sun rise at 7:49 ( 8:49 loacl time at 15°W) I tried to use the 'red light off' moment as my local SR time. this was at 9:10. So I am 21 minutes behind the SR time for 15°W which would mean that I am ~5° farther west, so at ~20°W, which would meet my real longitude well (still being ~20.5°W). I am not sure what to take as my referring point for the SR yet but the moment when red light turns off (= sun is to be seen by half of it's amount) fits well in this example. I will test this a little further tomorrow. __________________ My Subskins: http://www.subsim.com/radioroom/showthread.php?t=164169

06-27-07, 08:47 AM	#71
don1reed Ace of the Deep Join Date: Dec 2004 Location: Valhalla: Silent Generation Posts: 1,149 Downloads: 910 Uploads: 0	Its a hard grapple, I know. For me, the frustration level mounts daily...not good for an old fart with bad ticker Something worth knowing: 1)Those SR/SS tables, both van's and IRL are in "LOCAL TIME". Its up to the mariner to compute UT (GMT). 2) Are we taking into account DayLight Time/DayLight Savings Time ? 3) I found out yesterday, while sailing NW in U.47 (AP 55° N, 7° 31' E), that the lower (white background) clock in SH3 dropped back one hour when the boat crossed meridian 7° 30' E, the boundary line between Prime Meridian 000° and 015° east. edit: I'm going to replay this, just to make sure.... __________________ [SIGPIC][/SIGPIC] During times of universal deceit, telling the truth becomes a revolutionary act. ~ George Orwell

06-27-07, 06:18 PM	#74
ichso Ace of the Deep Join Date: Jul 2005 Location: Germany's oldest city alive Posts: 1,066 Downloads: 57 Uploads: 0	The method I mentioned, using the moment when red light turns off as your SR time, seems to work well. Just know your latitude as precise as possible. From Van's SR/SS almanac get the current local SR time by interpolating between the next bigger and next smaller given lat.value there. Then just wait for the exact red-light-off-moment (minute wise) and get the difference from the above calculated SR time. This time difference is needed in hours, for example are 75 minutes of time difference to be used as 1.25 hours. Multiply that number by 15 and that are the degrees your off from Greenwich. I worked myself from the coast of Northern Africa up to Scotland and from there back to St.Nazaire with very good results of position calculations. Had no ship encounter on the hole patrol though, nearly ran out of fuel before returning to base __________________ My Subskins: http://www.subsim.com/radioroom/showthread.php?t=164169

06-28-07, 12:58 AM	#75
Mav87th Stowaway Posts: n/a Downloads: Uploads:	We are basicaly working with 3 "times" here BASE TIME: Gameclock (in SH-4 thats easy as there is only one! In SH-3 Don's findings shows that its NOT the one with white background) GMT: Well that says it self. Van's SR/SS almanac is GMT times for SR/SS at 10 different lattitudes for each date all year in 1939 (Valid for all the war years) LOCAL TIME: The "missing link". The time we need to convert the two others into in order to make our calculations. (Or if you want to skip that then convert all the SR/SS's into BASE TIME or vicaversa GMT's to BASE TIME) Those convertions are what i ****ed up the most in the start, now im starting to get the hang of it. Just crossed the I-dateline in SH-4 after a great start from PEARL. First Sunset at around Lng 177E sat me 30nm off my real Lng. Im now waiting for the stars to shine through so i can take a fix on a couple of low stars. (I have found when using stars hanging low on the horizon to be most precise). The fast and easy thing would be to shoot Polaris and take that reading for granted for Lat., witch is the way i do it when crossing the pond on the long jurneys. Then ocationally i take a 6 star fix and calculate the position from the star GP's etc etc. with Navigator. That takes me within 15nm most of the times (when im controling it) Redlight time in SH-4 is DEFINETLY the correct SS/SR time - only thing missing is seconds in van's almanac to make it more precise, but i can get that from Navigator. It's correct that you need to know your Lat. pretty precise, but if you sail a heading for an amount of time you are not going to end up to far from where you plan, unless you fastforward x1024 or more. In that case you have to sit "watch" at the helm and click it every time it strays from the course.