Tom Evans schrieb:
Our data-model does not support earth as a sphere.
Uh? The data model supports it fine as far as I can see.
Yes, virtually all the tools don't, because it isn't a problem so far (and is
harder...). But they could be improved in the future and the data model would
be
Consider a way from 0°, -189.999° to 0°, 180°. that is, in our current
datamodel, a way that's roughly 40,000 km long.
No. In the datamodel, it's just a way between two nodes.
The nodes are defined in lat, lon, effectively in spherical co-ordinates,
hence them being angles. (ignoring
if the polygon is p1,p2,p3,p4...
c = centre point of polygon
v1 = the vector from c to p1 (p1 - c)
v2 = the vector from c to p2 (p2 - c)
take the cross product of v1 and v2
http://en.wikipedia.org/wiki/Cross_Product
if its positive in the z axis its one way, if its negative its the
On 28 May 2008, at 21:35, Richard Duivenvoorde wrote:
Richard Fairhurst wrote:
Can anybody point me in the direction of an algorithm that will
determine whether a closed way (polyline) is clockwise or anti-
clockwise?
cheers
Richard
___
dev
SteveC wrote:
On 28 May 2008, at 21:35, Richard Duivenvoorde wrote:
Richard Fairhurst wrote:
Can anybody point me in the direction of an algorithm that will
determine whether a closed way (polyline) is clockwise or anti-
clockwise?
cheers
Richard
On 29 May 2008, at 09:47, Richard Duivenvoorde wrote:
SteveC wrote:
On 28 May 2008, at 21:35, Richard Duivenvoorde wrote:
Richard Fairhurst wrote:
Can anybody point me in the direction of an algorithm that will
determine whether a closed way (polyline) is clockwise or anti-
clockwise?
The Geos Library has a method isCCW (counterclockwise) - (
http://geos.refractions.net/ro/doxygen_docs/html/classgeos_1_1algorithm_1_1CGAlgorithms.html
).
Unfortunately this algorithm is not exposed in the Geos C API (only the C++
API), and thus not available in the Python etc bindings - but the
On Wed, May 28, 2008 at 10:26 PM, Richard Fairhurst [EMAIL PROTECTED]
wrote:
Can anybody point me in the direction of an algorithm that will
determine whether a closed way (polyline) is clockwise or anti-
clockwise?
Take a look at this:
SteveC wrote:
On 29 May 2008, at 11:08, Richard Fairhurst wrote:
For anyone interested, this is the code I committed at silly o'clock
last night:
[...]
its amazing any of that works
How so?
cheers
Richard
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SteveC wrote:
it's like reading undocumented assembler!
I could do that if it helps?
ld hl,table: call BD58
ld hl,BD2B: ld de,mc_pc: ld bc,mc_pco: call patch
ld hl,BD31: ld de,mc_sp: ld bc,mc_spo: call patch
ld hl,BDF1: ld de,mc_wp: ld bc,mc_wpo: jp patch
Our data-model does not support earth as a sphere.
Uh? The data model supports it fine as far as I can see.
Yes, virtually all the tools don't, because it isn't a problem so far (and is
harder...). But they could be improved in the future and the data model would
be fine. Or am I missing
On 29 May 2008, at 13:17, Dave Stubbs wrote:
On Thu, May 29, 2008 at 9:07 AM, SteveC [EMAIL PROTECTED] wrote:
if the polygon is p1,p2,p3,p4...
c = centre point of polygon
v1 = the vector from c to p1 (p1 - c)
v2 = the vector from c to p2 (p2 - c)
take the cross product of v1 and v2
Can anybody point me in the direction of an algorithm that will
determine whether a closed way (polyline) is clockwise or anti-
clockwise?
cheers
Richard
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dev@openstreetmap.org
Richard Fairhurst wrote:
Can anybody point me in the direction of an algorithm that will
determine whether a closed way (polyline) is clockwise or anti-
clockwise?
cheers
Richard
___
dev mailing list
dev@openstreetmap.org
On May 28, 2008, at 1:35 PM, Richard Duivenvoorde wrote:
Richard Fairhurst wrote:
Can anybody point me in the direction of an algorithm that will
determine whether a closed way (polyline) is clockwise or anti-
clockwise?
Richard,
there is a good set of (explanations of) algorithms here:
Nathan Vander Wilt schrieb:
On May 28, 2008, at 1:35 PM, Richard Duivenvoorde wrote:
Richard Fairhurst wrote:
Can anybody point me in the direction of an algorithm that will
determine whether a closed way (polyline) is clockwise or anti-
clockwise?
Richard,
there is a good set of
Thanks Richard and Nathan for the pointers - really appreciated. I
think I've got it now.
Nathan Vander Wilt wrote:
[...]
That said, I'm guessing there are other assumptions being made
within OSM that break down under spherical geometry. If your polygon
doesn't contain pole(s) or cross
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