I'm not an expert on this but I think floating point arithmetic is not absolutely precise. For example my computer gives this result 0.1*0.1 = 0.010000000000000002. I think it has to do with the fact that some numbers (like 0.1) are periodic when expressed in binary and computers can only store a finite number of decimals. Maybe you can work with a tolerance.
On Tue, May 19, 2009 at 2:03 PM, Anke Trittenbach <[email protected]>wrote: > Hello all together, > > I have a problem and I hope you can help me with this. > > My intersection operation for geometries doesn’t return the correct result > when the geometries have many decimal places. > There is a method for checking if a point lays on a straight line. In this > method the slope and the intersection with Y-Axis of the straight line is > calculated. With this and the x-coordinate of the point the method > calculates the y-coordinate which should the point have if the point would > lay on the straight line. Then this and the real y-coordinate will be > compared. If they are equal the point lays on the line. But this doesn’t > work correct. Sometimes the method returns that the point does not lay on > the straight line, because the calculated values differ with a value of > 0.000000000004. But in reality the point lays on the straight line. > > Does somebody know if the calculation is wrong? Or how did you avoid such > kinds of problems? Does this problem maybe deals with the precision or the > tolerance? > > With kind regards and thanks for your help. > > Anke Trittenbach > > -- > Neu: GMX FreeDSL Komplettanschluss mit DSL 6.000 Flatrate + > Telefonanschluss für nur 17,95 Euro/mtl.!* > http://dslspecial.gmx.de/freedsl-surfflat/?ac=OM.AD.PD003K11308T4569a > _______________________________________________ > jts-devel mailing list > [email protected] > http://lists.refractions.net/mailman/listinfo/jts-devel > -- Fernando González Cortés Ingeniero informático, http://fergonco.scienceontheweb.net
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