Neutrino
03-18-09, 07:18 AM
I only started playing SH3 a short while ago but one of the things I noticed was that using the stadimeter I appeared to be getting consistantly long readings for the range on some ships, errors in the order of several hundred meters at 5km, I think I have now found the cause of that.
The ship recognition manual and game config files list the highest point on the ship as the mast height. I'm not sure this is authentically accurate. I was under the impression that the mast height on the ship is supposed to be the height of the tallest mast proper, that is not includings flags, penant holders, antenna or whatever else might be hanging off the mast. I can't find a reference for this atm so if anyone knows for sure please pipe up.
The reason for this would be obvious. Thin antenna, pennant holders and the like will be invisible in low visibility.
So what I have been doing is taking a range measurement at the top of the mast head, which at long range or in poor visibility is likely to be the highest point on the ship you can see, and the notebook has been using a different point on the ship that I can't see as the reference point, and that's been the cause of my error.
I've had a think about it to try and work out what might be the best way around this. I can measure the actual height of the mast head quite easily. I think I've found the files containing the ship recognition data and the data used by the stadimeter. It seems to me that the following could be one possible solution:
1. Measure the height of the mast head.
2. Update the ship recognition and ship config data with that new height.
3. Update the picture of the ship in the recognition manual to include a faint red line to indicate at which point the height reading was taken.
I'd be interested to hear what the rest of you think of that.
1. Has it already been done?
2. Is it likely to be as straightforward as I suspect?
3. Is there a better way?
One final consideration.
Makman94 has mentioned he has a mod which uses funnel height to achieve a similar end. I have a few concerns about that approach, but I'm not sure how valid they are so your views on that would also be appreciated.
In situtations where the target presents a small aspect to you, ie you're almost directly ahead or astern of it you may have trouble identifying the top of the funnel. It may be obscured by superstructure. Large cargo ships can have 4 or more cranes, the ones in front of the funnel will always obscure it, in darkness where all you see is a silhouete the masts both in front of and behind the funnel will blot it out. One of the main advantages of stadimetric rangefinding is that it works no matter what angle the target presents to you. For the reason just stated using the funnel as a reference point risks undoing that advantage.
The advantage of using the funnel is that in many cases it is more centrally located than the heighest mast, which for a large ship presenting a small aspect gives you a fix closer to the center of the ship, which should be more accurate than getting a fix on a mast near the bow or the stern.
I can forsee a couple of problems with this.
Firstly the advantage of getting a fix on the center of target is only really useful if the ship is presenting a low aspect to you, (if it's broadside on a range at any point along it is good). But it's precisely when the target presents a small aspect that getting a fix on the funnel is likely to be more difficult.
Secondly. The funnel is likely to be significantly lower than the tallest mast. For stadimetric rangefinding the higher the reference point the more accurate the reading. So by using the funnel as a reference point you risk getting a less accurate result to start with.
And one final point.
If you're taking a range fix on a large ship that is presenting a small aspect or travelling directly away from you, the smart captain will know that if the ship is 100 meters long and he's taking a fix on a mast near to one end of it he should add 30 meters or however much from his calculation as appropriate. In this manner smart play and experience provide the rewards of a better outcome, which I like.
In conclusion: This is unlikely to be something I'll be able to knock out in a week or two, I have a lot of RL coming up. But I might make a start on it for my own satisfaction, and before I embark on that I just wanted to check with you guys that I haven't overlooked any important considerations.
Thanks.
The ship recognition manual and game config files list the highest point on the ship as the mast height. I'm not sure this is authentically accurate. I was under the impression that the mast height on the ship is supposed to be the height of the tallest mast proper, that is not includings flags, penant holders, antenna or whatever else might be hanging off the mast. I can't find a reference for this atm so if anyone knows for sure please pipe up.
The reason for this would be obvious. Thin antenna, pennant holders and the like will be invisible in low visibility.
So what I have been doing is taking a range measurement at the top of the mast head, which at long range or in poor visibility is likely to be the highest point on the ship you can see, and the notebook has been using a different point on the ship that I can't see as the reference point, and that's been the cause of my error.
I've had a think about it to try and work out what might be the best way around this. I can measure the actual height of the mast head quite easily. I think I've found the files containing the ship recognition data and the data used by the stadimeter. It seems to me that the following could be one possible solution:
1. Measure the height of the mast head.
2. Update the ship recognition and ship config data with that new height.
3. Update the picture of the ship in the recognition manual to include a faint red line to indicate at which point the height reading was taken.
I'd be interested to hear what the rest of you think of that.
1. Has it already been done?
2. Is it likely to be as straightforward as I suspect?
3. Is there a better way?
One final consideration.
Makman94 has mentioned he has a mod which uses funnel height to achieve a similar end. I have a few concerns about that approach, but I'm not sure how valid they are so your views on that would also be appreciated.
In situtations where the target presents a small aspect to you, ie you're almost directly ahead or astern of it you may have trouble identifying the top of the funnel. It may be obscured by superstructure. Large cargo ships can have 4 or more cranes, the ones in front of the funnel will always obscure it, in darkness where all you see is a silhouete the masts both in front of and behind the funnel will blot it out. One of the main advantages of stadimetric rangefinding is that it works no matter what angle the target presents to you. For the reason just stated using the funnel as a reference point risks undoing that advantage.
The advantage of using the funnel is that in many cases it is more centrally located than the heighest mast, which for a large ship presenting a small aspect gives you a fix closer to the center of the ship, which should be more accurate than getting a fix on a mast near the bow or the stern.
I can forsee a couple of problems with this.
Firstly the advantage of getting a fix on the center of target is only really useful if the ship is presenting a low aspect to you, (if it's broadside on a range at any point along it is good). But it's precisely when the target presents a small aspect that getting a fix on the funnel is likely to be more difficult.
Secondly. The funnel is likely to be significantly lower than the tallest mast. For stadimetric rangefinding the higher the reference point the more accurate the reading. So by using the funnel as a reference point you risk getting a less accurate result to start with.
And one final point.
If you're taking a range fix on a large ship that is presenting a small aspect or travelling directly away from you, the smart captain will know that if the ship is 100 meters long and he's taking a fix on a mast near to one end of it he should add 30 meters or however much from his calculation as appropriate. In this manner smart play and experience provide the rewards of a better outcome, which I like.
In conclusion: This is unlikely to be something I'll be able to knock out in a week or two, I have a lot of RL coming up. But I might make a start on it for my own satisfaction, and before I embark on that I just wanted to check with you guys that I haven't overlooked any important considerations.
Thanks.