Omission in interpolation calculation Z_GROUND in PROFILE table

[shaswin]

Affected PLE version: 4.2.3

Hello, there is a omission in the calculated values of Z_GROUND in the PROFILE output table. An example is given below:

[attachment=548]

The educational PLE project file (zipped) has also been attached for the analysis.

At the 'start' (node 6) and 'end' (node 22) of the bend I get a Z_GROUND of 1707.1 mm in AutoCAD. PLE gives in the PROFILE output table a Z_GROUND of 1655 mm at the bend ends, see picture below:

[attachment=549]

This calculation error is always reproducible when bends are used in the POLYDIF.
Column W_LEVEL in the PROFILE table is also affected with the same error.

I have also tried different configurations in AutoCAD to verify the Z_GROUND. The error of the Z_GROUND at bend nodes are structural in PLE.
It is important that the Z_GROUND is correct, because PLE uses the PROFILE output table in the Soil Model Wizard to calculate the soilparameters.

[shaswin]

Another example:

IDENT D20B1s: node 10, Z_GROUND PLE: 1641 mm, AutoCAD: 1621.6 mm
IDENT D20B1e: node 20, Z_GROUND PLE: 1496 mm, AutoCAD: 1475.2 mm
IDENT D20B2s: node 24, Z_GROUND PLE: 1176 mm, AutoCAD: 1169.9 mm
IDENT D20B2e: node 28, Z_GROUND PLE: 1148 mm, AutoCAD: 1148.5 mm
IDENT D20B3s: node 37, Z_GROUND PLE: 1767 mm, AutoCAD: 1762.5 mm
IDENT D20B3e: node 43, Z_GROUND PLE: 2000 mm, AutoCAD: 2000.0 mm

There is also difference in this example.

Column W_LEVEL in the PROFILE table is also affected with the same error.

[Ing. Henk Olie]

Omission in interpolation calculation Z-GROUND.

Although this remark is understandable, Ple4Win calculates the Z-GROUND values as intended.

IDENTS are linked to NODES. Defining G-LEVEL using IDENTS means input is provided for nodes 1, 12 and 23. The other nodes (2-11 and 13-22) will get interpolated values.
As nodes are always located on the pipeline axis, interpolation is done using the AX-L value of the nodes.

   

The resulting Z-GROUND of node 4 is 1654.710 leading to a soil cover of some 948 mm

Using X coordinates (0, 1000 and 2000 mm) as input for G-LEVEL the Ple4Win generated
Z-GROUND values will form straight lines, and results in a Z-GROUND of 1707.107 mm.

Of course we can discuss a different approach in the future.

Please refer to the screen shot.

   

[shaswin]

Your point is clear. There is no need for a new approach, because the differences are small in the most cases.