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posted: 14 May 2020 11:46 from: Martin Wynne
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David G has asked me a question to which I know the answer. But I don't know how to explain it in words. There are two ways to create a diamond-crossing in Templot: 1. peg/align tools > make diamond-crossing at intersection This more often than not produces an irregular diamond. The maths is optimized towards preserving the underlying curving and radii. 2. tools > make diamond-crossing tools > make slip crossover tools > make ladder crossover This produces a regular diamond. The maths is optimized towards maintaining the crossing angles and track spacings. There are some situations where either method could be used -- but in curved track, method 2 produces a slightly different result from method 1. So the obvious question is -- which method do you use in any given situation? If it's closely connected to other pointwork it would normally be method 2. But not always -- a double-junction often requires method 1 for example, and likewise in curviform ladders. Looking at a track plan I can immediately see which method is required. But it's difficult to find the words to explain it.* Any help gratefully received. In an ideal world, Templot would use much more complex maths for the curving calculations, so that both methods produce an identical result. But we are not in an ideal world -- and nor were the track designers in the bullhead era. Even less so the gangers who then laid it. Like them, Templot needs a big hammer. *OS map makers face a similar problem with ornamental parkland. Everyone knows it when they see it: http://goo.gl/maps/gieHhkLay9gr2J6g7 But how do you define it in words to differentiate it from ordinary farmland? cheers, Martin. |
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