Wednesday, 19 November 2014

Project North don't do it!

Project North

English version of: project-north-niet-meer-doen

Several times I have written about coordinates in Revit. Recently I have seen a number of projects where errors with coordinates creep in. Often I see architects who get a drawing from the municipality drawn to coordinates and then they pick an interesting point in the drawing as an exchange point. This work quiet well in Autocad. I don't advise it for working in Revit.

First of all when you pick a point in you drawing you will get a point with lot's of decimals and therefore you will get differences in rounding when usinging different software packages. I suggest you create a point and you move it to rounded the coordinates. I have this little Autocad block that I use for it.

I also have to admit that in the past I have explained people how to acquire coordinates from a dwg. I have stopped teaching this and using this methode because it creates inaccuracies. I also have stopped with using Project North. I have experienced quiet a few annoyances when trying to set it up. I have also experienced some major problems in projects with multiple disciplines. There was one project were the BIMguide said that the rotation was 60.389° while the project was really setup wit these numbers: 60,38872747670°
Read this little excel example as follows:

Row 3 is angle α and row 5 is β
In row 2 and 3 you see the length set for x and in row 3 you see the lenght for y

So when α = 60 then x = 1000mm and y = 1732,05mm
If α wasn't 60 but instead rounded down from = 60.4 and x = 1000mm then y becomes 1760,32 mm. This is means that because of this rounding the differences becomes (f) 28,27mm. (btw verschil = difference)

In Row 12 you see the difference between if the angle is 60,389 and 60,3887. If X is a meter you can't tell the difference. But when X becomes 1000 meter than the difference is almost 2mm. This will make clashdetection a hell! How to avoid it?

Do not use project north for drawing orthogonally! Use scopeboxes! Also be aware Project north will only let you do one rotation per file. Scope box  will let you do as many as you can deal with.

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