# Talk:Relations/Proposed/Curvature

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## Which projection

For which projection is the assumed "straight" valid?

I admit that I didn't think about the projection when I wrote the proposal. However, "straight" means straight in the real world, in other words a great circle (if it's valid for a geoid). It is a secondary issue how it will look like with a particular projection. If one knows that a certain way is really straight, tagging it somehow will permit an editor (program) to straighten it (and to keep it straight). --Mikalaari 15:28, 14 April 2010 (UTC)

## Wrong assumption

Often ways are not straight and angles are not 90°. 100% of the mappers have never measured a house with a ruler.

Prominent example:

http://www.openstreetmap.org/?lat=52.38807&lon=9.69712&zoom=16&layers=0B00FTF Yes, this is not rectangular!

Do you mean that (in most cases) it is too difficult to tell if a way is straight or just straight enough to make an observer think it's straight? In think there's a bit of truth in that, but in doubt one wouldn't put the "straight" tag on the way. Also, when the assumption that a way is straight does not match a GPS track, for example, this relation shouldn't naturally be used.
What comes to right angles, it is totally irrelevant to this proposal. Tho closest thing it has is a role ("cusp") for indicating the nodes at which the way changes direction in any angle. By default it is assumed that the way is smooth and the polygonal path is just an approximation. --Mikalaari 15:47, 14 April 2010 (UTC)