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Guest cwright

Simple way to change coastlines

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I'm investigating the possibility of writing a utility to modify coastlines.I'm aware of Ground2K and Coast Line Maker... but they seem quite time consuming to use for large areas.What I want to do is have my utility take an input file of points (longitude and latitude) and have it generate the appropriate BGLC code ready for compilation to a BGL.This way users of the utility can quickly build better coast lines by simply suppling the coastline input file.For example, there's some good quality US coastline data available herehttp://rimmer.ngdc.noaa.gov/coast/in particular the NOAA/NOS Medium Resolution data (1 : 70,000) which is better than the default FS2002 data (which I believe is the World Vector Shoreline 1 : 250,000)I have seen the LWM tutorial written by Richard Ludowise "rhumbaflappy".Richard, do you think what I'm proposing to do is feasable?Im not sure whether the upcoming FS2004 SDK will make this any easier, but it can't be too hard, can it?Are there any pitfalls you can see? Have I underestimated the complexity of the coastline BGLC coding?Does anyone else have any thoughts.Matthew.

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Have I understood this correctly?Basically the surface of the FS2002 world is divided into LOD13 "cell areas" and is of two types. Either land (as defined by a landclass) or water (as defined by a water class).Of course LOD13 cell areas are square in shape and so to define the actual coastline it needs to be "cut" into a landclass cell area using a LVM polygon.Actually I might go explore ground2k and coastline maker a little more, to get a better understanding.Matthew.

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The SCC-program can use that kind of shorelines as background, so it is easy to rebuild shorelines using this program. You can then store the rebuild shorelines as SCASM-files and those files can be translated to ASM-files by the SCM2VTP-program to create the new shorelines and by the SCM2LWM-program to create the corresponding LWM-masks.

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Matthew as explained the difficutyThe solution depends on the wanted level of automatation.First, the line : not a problem in itselfSecond, the water and/or land polygons you have to generate.At the moment you generate these polygons, generally, you don't know where is the old FS coastline.It could be a clever solution :- draw the old FS shoreline (in your program)- draw the new shoreline (in your program)- try to create land polygons between these two lines when necessary- generate water polygons along the new coastline with sizes to determinate (for example 1 miles along the new coasline) or draw a 3rd line that would show where to limit the water polygons.Think also that your generated water polygons could cover existing FS island;Generate convex polygons because FS don't like sometimes complicated concave polygons.Sometimes users must add landclasses in order that the terrain shows up on some old FS water locations.Not so difficult, but is it the right and quicker solution for users ?Christian

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Hello Matthew,Dick is rather busier now than before, so he may not answer you right away here. Perhaps you could write to him directly for a faster response.He has put together a few macros that should help in your task. You will find them with just about all the terrain design programs that are available.Just a few terms that are used in terrain modification:- the smallest unit of display is a Point. This has an approximate resolution of 4.77 meters.- LOD13 is referred to as an Area. It consists of 256 x 256 Points.- LOD8 is called a Cell. This is 32 x 32 Areas.- LOD5 that is 256 x 256 Areas(The LOD grid is not square, as you know, but has a resolution that varies according to latitude. Vertical resolution is always 4.77 meters per point but horizontal resolution can be quite different and may affect the shapes that are drawn. For example, I am working on a large project covering the tepuis of Venezuela (N6*) with a horizontal resolution of 6.32 mpp, whereas as I did a scenery of the French Mediterranean (N43*) with a horizontal resolution of 4.59 mpp.)The importance of these terrain units is that terrain is often limited to their boundaries. For example, lines and polygons may not cross over into another Area.If you take a look at Christian Fumey's Ground2k, you will see that, while he allows the user to draw lines as long as they want, he then must proceed to break them up according to their Area. And so will you if you want to automate this procedure.In addition, as Christian mentions, you may only use convex curves, so you must also break up all lines in order to avoid concave curves.Coasts and shorelines are two different terrain features. A coast is a polygon that is masked as land, then a shoreline is drawn along the water edge of that polygon - a shoreline is a polygon that displays the relevant texture (VTP).Like the FS Development Team, you will have to contend with the complexity of this process, that is, how do you know what type of shoreline should accompany a coast? White sand beach? Harbor? River bank? How wide should this shoreline be? Also, inevitably, at some parts, there will be gaps between the coast and the shoreline when they do not coincide perfectly or where the line width is insufficient.As Christian points out, you must also exclude the default shoreline before creating the new one.And, in many Areas, you will be creating a coast where land has not been declared, so nothing will show up unless you Fill with Land first (in fact, you should probably just do this as a first step anyway.)There are other pitfalls as well, for example, the shape of your land mask polygon must be drawn in such a way that it does not cross over itself, easy to do when you are drawing small coasts, but more difficult with the large coasts that you propose.You must also take into account the importance of Layers and Excludes, and be careful of how you generate the final bgls so that they respect the order required by Flight Simulator so as to be read correctly.You have chosen a very worthy task and one that many have often requested. Good luck to you.Best regards.Luis

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Matthew, my AutoAsm program can be used to trim coastlines - and it has an import function for precisely the format you mention! A quote from the instructions: COASTLINE IMPORTNote: this feature is incomplete. AutoAsm can import coastline files obtained at: http://rimmer.ngdc.noaa.gov/coast/ Here

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