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#1
josie

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Hi everyone,

Sorry to bother you all again! I want to plot a ship through a narrow passage. This is no problem, but I want to show the actual dimensions of ship rather than it as just a dot. I have the autocad file of the ship (in 2d) and also the dimensions in text. Is it possible to show this ship in real metres? As in not a dot but as a real thing with real dimensions???

Any help would be great as I have not done this before!

Thanks

Josie

#2
Hans van der Maarel

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Sorry to bother you all again! I want to plot a ship through a narrow passage. This is no problem, but I want to show the actual dimensions of ship rather than it as just a dot. I have the autocad file of the ship (in 2d) and also the dimensions in text. Is it possible to show this ship in real metres? As in not a dot but as a real thing with real dimensions???

Any help would be great as I have not done this before!


Do you want to track it in realtime? What software?
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#3
josie

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If possible I wouldn't mind tracking in realtime but if it isn't possible then I will not mind too much. I wondered if I could make it a bmp or tiff and then add it as a style. Then plot points and change the symbology for the image. However, would it still keep the right dimensions? I am not sure.

#4
Hans van der Maarel

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If possible I wouldn't mind tracking in realtime but if it isn't possible then I will not mind too much. I wondered if I could make it a bmp or tiff and then add it as a style. Then plot points and change the symbology for the image. However, would it still keep the right dimensions? I am not sure.


I was going to suggest this method as well. It would depend on knowing the heading of the ship (so the symbol can be rotated) though.

The tricky bit would be to give it the correct size. You could figure out what the correct symbol size would have to be, but that only works on one set scale. If the user zooms in or out, you really ought to scale the symbol too.
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#5
josie

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If possible I wouldn't mind tracking in realtime but if it isn't possible then I will not mind too much. I wondered if I could make it a bmp or tiff and then add it as a style. Then plot points and change the symbology for the image. However, would it still keep the right dimensions? I am not sure.


I was going to suggest this method as well. It would depend on knowing the heading of the ship (so the symbol can be rotated) though.

The tricky bit would be to give it the correct size. You could figure out what the correct symbol size would have to be, but that only works on one set scale. If the user zooms in or out, you really ought to scale the symbol too.


I do know the heading of ship. I have an excel file of the ships lat and long at various points and also its heading. I also have a dwg file and dxf of the block. Is it possible to rotate according to the heading? I'm not sure how to do that actually. This is actually something very new to me.

I agree with you in regards to scale, that is a tricky one. The problem is it cannot be wrong even by a little bit because the point of it is to show hoe the size of the ship will affect the manouver.

#6
josie

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Ok, so now I have done it. I made the file a bitmap and then scaled it. I specified that I wanted the symbol to be scaled and set a reference scale. I have set the heading based on the advanced symbol options and geographic heading.

Along the vessel is a point. This point is the locations where the coordinate location is recorded from. This has also been lined up precisely in my bitmap and so this is all fine. But, for some reason the ship is slightly offset in some places. Can anyone think of a reason for this? I have tried to add a small angle but, though it corrects in one place, it goes wildly off in another.

Any ideas would be greatly appreciated.

josie :)

#7
Unit Seven

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Ok, so now I have done it. I made the file a bitmap and then scaled it. I specified that I wanted the symbol to be scaled and set a reference scale. I have set the heading based on the advanced symbol options and geographic heading.

Along the vessel is a point. This point is the locations where the coordinate location is recorded from. This has also been lined up precisely in my bitmap and so this is all fine. But, for some reason the ship is slightly offset in some places. Can anyone think of a reason for this? I have tried to add a small angle but, though it corrects in one place, it goes wildly off in another.

Any ideas would be greatly appreciated.

josie :)


Maybe check the centre of the bitmap is also the centre of the ship shape (pun intended) so that the ship is rotating correctly. If the rotation point was toward the front or back of the ship then it would move the ships shape off the line at some bearings.
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#8
josie

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Yes the centre is in the correct place, it is not in the middle of the ship indeed but I already placed it into the correct place. I believe the problem may be to do with the projection. You see this was originally plotted in autocad and is now in GIS. The ship is not wrong but it is slightly off at an angle, yet still where it is meant to be. In Autocad this was still plotted in the same coordinate system but I wonder if it is to do with maybe the fact that Autocad is a flat projection?




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