[Manifold-l] On screen digitizing of curves

[Pat Waggaman]

Interesting if one of the sages pops up and says 
that "curves" can be created in ESRI 
software.  Perhaps it is so, I suspect that at 
some point the creation of a "curve" runs into 
the mathematical expediency of Epsilon in its 
representation; particularly when said curve is 
calculated by a digital processor.

Meantime what I´d do is tightly digitize the 
orthophoto and, using the Segmentize control 
reduce the segment length between your points to 
somewhere between a couple of centimeters and the 
beautiful 1/1,000,000 meter resolution that can 
be achieved with the Manifold grids.

And then you´re in the spectacular negotiating 
position of asking your client to balance the 
cost of the ESRI system with the nanometer error 
that you are introducing.  At some point in the 
discussion it will arise that the errors you 
introduce are orders of magnitude less than the 
potential errors created by the difficulty of the 
ESRI operator in locating the center points, from 
which the curves will be created.

Have at it lad.

Pat


At 18:41 06-11-2007, Springfield Harrison wrote:
>         From the forum:
>
>Hello:
>
>A potential client needs on screen digitizing of 
>roads from an orthophoto but the curves cannot 
>be line segments. Apparently the ESRI 
>Geodatabase into which these data will go can 
>define curves with a start, end and radius.
>
>This may be so but how can OSD be used to create 
>curves in Manifold, or anything else for that 
>matter. I think OSD can only create straight 
>segments joining mouse clicks. Even stream 
>digitizing is a series of very closely spaced dots, I think.
>
>Can this actually be done as required by the proponent using OSD?
>
>Thanks very much, Springfield
>
>                            Spring Harrison
>                                       Stellar GPS & Mapping
>                                 103 - 9800 McDonald Park Road
>                                        Sidney, B. C. Canada
>
>                                          www.StellarGPS.ca
>
>                                  Voice, 24 hr: (250) 655-0764
>                                     Toll free: (888) 655-0764
>                                         Fax: (250) 654-0049
>
>_______________________________________________
>Manifold-l mailing list
>Manifold-l at lists.directionsmedia.net
>http://www.directionsmedia.net/mailman/listinfo/manifold-l
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.directionsmedia.net/pipermail/manifold-l/attachments/20071106/f33bb9db/attachment.html