I hope the translation from spanish works.
When I got into geography at U Catolica of Santiago, they made us a test.
My first university test!!!.
On question 8 there was this one:
You are on a given point on earth, you walk 30 kilometres south, then turn
90 degress and walk 30 kilometres due east, then an other 90 degress turn
and you walk the same 30 kilometres and you not only arrive to the same
point, but ¿which color is the bear that is waiting for you messsing in your
camp?
Juanse
PD: Arc = Bear = Oso
An = no, contrario, opuesto
----- Original Message -----
From: Jacques Paris <[EMAIL PROTECTED]>
To: David Booth <[EMAIL PROTECTED]>;
<[EMAIL PROTECTED]>
Sent: Wednesday, April 11, 2001 10:19 AM
Subject: RE: MI-L Line attributes
> David,
>
> The issue of curved lines has not been clarified by the sender of the
query,
> but Bill Thoen framed the problem in MI terms quite explicitly.
>
> Your contribution about selecting curved polylines by using
objectgeography
> adds confusion to the subject because, in MI, curved forms exist only as
ARC
> objects and the attributes you use for that function apply only to ARC
> objects; you could have selected those forms more precisely with
objectinfo
> for type=arc. That means that all the considerations about S shapes are
> factitious and that your approach is irrelevant when dealing with
polylines.
>
> My view of the world translates into a curved geography; for me, pure
> straight lines do not exist in reality, straight line segments are only
> approximation of real shapes, the quality of the approximation depending
on
> the scale and the coordsys used. The presence of a node is enough for me
to
> indicate a change in direction (a curve?); but a change of direction is
not
> enough to define a "curved" portion; the intensity of the change must be
> defined and only the user can specify it.
>
> Jacques
>
> Jacques PARIS
>
> [EMAIL PROTECTED]
>
> For MapInfo support, see the Paris PC Consult enr. site at
> http://www.paris-pc-gis.com
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of David Booth
> Sent: April 11, 2001 4:36 AM
> To: '[EMAIL PROTECTED]'; [EMAIL PROTECTED]
> Subject: RE: MI-L Line attributes
>
> Hi Peter,
>
> As Bill Thoen says, a "curved" polyline is made up of straight segments,
so
> to determine if it is curved, you need to work out if segments run in the
> same direction as each other.
>
> You should be able to knock something together using mapbasic.
Objectnodex()
> and Objectnodey() will return coordinates for the nodes on a polyline,
then
> some variation on
>
> tan(angle) = (y2-y1) / (x2-x1)
>
> Where
>
> angle = the angle of the segment
> x1,y1 = coords of first node
> x2,y2 = coords of second node
>
> for each segment - if the angles differ then the polyline is curved.
>
> If this sounds horrible, you could probably do a quick and dirty check
> using:
>
> select where objectgeography(obj,OBJ_GEO_ARCBEGANGLE) <>
> objectgeography(obj,OBJ_GEO_ARCENDANGLE)
>
> which would select curved polylines, except those where the last segment
> goes in the same direction as the first (eg S or Z shapes).
>
> Anyway, it's far too early in the morning for me to dredge up trigonometry
> from my schooldays, so I'm off for a coffee.
>
> Hope this helps, and my trig. is right!
> ---------------------------------------------
> David Booth
> Senior GIS Officer
> Merseyside Information Service
>
> > -----Original Message-----
> > From: [EMAIL PROTECTED] [SMTP:[EMAIL PROTECTED]]
> > Sent: 10 April 2001 18:28
> > To: [EMAIL PROTECTED]
> > Subject: MI-L Line attributes
> >
> > Greetings,
> >
> > I think this should be a simple request. I am wondering if anyone knows
of
> > a technique to select a portion of a polyline that may have a curvature.
I
> > have a number of polylines that I would like to select only the portion
> > which curves.
> >
> > Your thoughts and suggestions are welcome.
> >
> > TIA
> >
> > Cheers,
> >
> > Peter
> >
> > ___________________________
> > Peter McPherson
> > GIS Technician
> > Cameco Corporation
> > 2121 11th Street West
> > Saskatoon, Saskatchewan
> > S7M 1J3
> > Canada
> >
> > Telephone (306) 956 6433
> > Fax (306) 956 6390
> >
> >
> >
> >
> > _______________________________________________________________________
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>
>
>
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