What interpolation method does a Characteristic Diagram use?

[PorridgeMan]

Hello,

Does anyone know what interpolation method is used when you create a Characteristic Diagram (3D contour chart) using a triplet of data? Interpolation implies that the fitted surface passes exactly through the data points. How is the rest of the surface calculated (interpolated)?

Am I right in saying the "Evaluation Points" in the diagram dialog box specifies a grid of x and y values for the surface to be evaluated at (by interpolation of the data points)?

I tried the online help, but it was a bit lacking in detail.

Thanks,

PorridgeMan.

[Walter_Rick · Accepted solution]

Hello PorridgeMan,

The SISPL algorithm is used for this.

The Smart Interpolating Spline Surface method combines a low computing time requirement with a high degree of smoothing quality. The method requires only a few settings. The method also accepts imprecise input data.

Greetings

Walter

[PorridgeMan]

Thanks Walter.

Was I right about the Evaluation Points business? I suppose so, I can't think what else it could really be.

Do you know if there's any more detail on SISPL method somewhere, e.g. a knowledgebase article? I couldn't locate anything myself.

Regards,

PorridgeMan.

[Walter_Rick]

Hi PorridgeMan,

Yes, you are right. The SISPL algorithm is using a grid for the interpolation. Sorry, but I don't have detaild information about this algorithm.

One note : Depending on the measured data (which should be displayed) you can use a "pre-process".

Partial load structure
Specifies for the display mode Contour whether triplet data is distributed free or in a partial load structure. This setting specifies the interpolation mode of the z-values. If you enable this setting, DIAdem lays y-z-splines with regular interpolation points in y-direction through the points of every partial load. Then DIAdem lays x-z-splines through the interpolation points in x-direction. A partial load is compiled of points whose x-values are in a narrow tolerance range.
Use the PartialLoadTolerance property to specify the maximum deviation of the x-value in a partial load as a percentage of the complete x-area. Points whose x-values lie outside the tolerance belong to a further partial load. If a partial load has fewer than three points, DIAdem terminates the display.

Greetings

Walter