Understanding Node Rotation Options

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This page aims to clarify and explain how the concepts of node rotation options relate to fields in the WinCan VX database.

Background

In most drainage inspection standards around the world, there is usually a definition of a ‘Radial Reference Point’ for manhole inspections, from which we can describe the location of defect observations and node connecting pipes to help us build up a picture of the structure of the manhole and its condition.

In most standards, this radial reference is described by the ‘most significant’ outgoing pipe and a clock reference. So the user must decide which pipes are outgoing and which are incoming, and then if there is more than 1 outgoing pipe, they must decide which one is the ‘most significant’ so that they can set the radial reference point for their inspection.

How we decide which is the ‘most significant’ is usually a matter of training, but most territories agree that it is the deepest pipe leaving the manhole, because when the rain comes down hard and the manhole begins to fill with water, this is the first pipe that fills with water.

We then define this pipe as being at a clock position as defined by the standard, and all other data recorded against the manhole is defined by the location of this reference point.

Standard Variations

The radial reference is always stored in the inspection table (NODINSP.INS_RadialRef) because it is inspection level data.

Some common countries have standard definitions like:

• Isybau

  • The radial ref can be 6 or 12 o’clock, so the user can define.

  • Means that a single project can have inspections where some are at 6 and others are at 12.

• UK has 3 different standards with 3 different versions:

  • WRc standard defines the radial reference as 6 o’clock.

  • HADDMS defines the radial reference as 12 o’clock.

  • STC25 manhole standard defines the radial reference as ‘North Up’.

How to Interpret this…

In the following images, all 3 manholes are the same. The only difference between each one is where you are standing over the manhole to look down and inspect the asset.

In all cases, if you consider the position of the outgoing blue pipe, and:

• Go 5 clock positions clockwise, you will come to the incoming red pipe.

• Go 4 clock positions anti-clockwise, you will come to the North direction arrow.

• See that the long side of the shape (the long axis dimension of the oval) is aligned with the 6 - 12 o’clock position.

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The only thing that is changing from the left picture to the middle picture to the right picture is the radial reference clock position, so:

• In picture 1, the radial reference is at 6 o’clock which means that as you look down the manhole, the outgoing pipe is going between your legs and behind you.

• In picture 2, the radial reference is at 3 o’clock which means that as you look down the manhole, the outgoing pipe is going to your right side.

• In picture 3, the radial reference is at 12 o’clock which means that as you look down the manhole, the outgoing pipe is going directly away from you.

But it is always the same manhole - the only thing that is changing when you change the radial reference is how you are looking at the manhole.

Using the Longside Reference

The WinCan VX field NODINSP.INS_LongsideRef is used to store information about the orientation of the long axis of a rectangular, oval or other irregular shape. The field has 6 possible numeric field values that should be used in the template like this:

The important points to note here are:

• The 6 o’clock position requires the item value zero for this to work correctly.

• There are only 6 clock positions in the list, because when we describe the direction of the long axis of the chamber as say 2 o’clock, then this is the same as saying 8 o’clock (opposite side of the clock face), so there is no need to have list 2 values here.

• This is the same setup for all standards and territories.

This field does not need to be visible in the VX node inspection header, but if it is then the user has additional controls. They can set the rotation of the chamber using the filed pick list or be using the ‘rotate’ button in the node 2D graph. One click of the button rotates the chamber by 1 clock position.

There is no problem with importing external data from a data file into this field, provided it follows the list items above of 0 - 5 (not 1 - 6).

So how does our manhole look now if we introduce a rotation of the long axis of the chamber? Again, as before, the manhole is exactly the same in all 3 images, and the only difference from the first to the third image is the radial reference position:

Using the North Direction Reference

The WinCan VX database field NODINSP.INS_NorthRef is used to store the clock position of the North arrow and this is a normal clock position pick list with 12 clock positions, because North can be in any direction relative to the outgoing pip reference position.

But, as described, the clock position of North will change when you change the radial reference, because they are linked together by their geometry on the ground.

This field can be used in the node inspection header and displayed with a pick list so that the user can specify the North direction arrow in the node 2D graph, and they can import this data from external files like those collected from GPS devices.

Rotating the Sketch To North

There are 2 new features planned for a future release of WinCan VX:

• Auto calculate the direction of North from the GIS pipe data, so on the click of a button, the INS_NorthRef will be set for all inspections where:

  • The radial ref is defined, and

  • The manhole has an outgoing pipe.

• A user option to always display the manhole ‘North Up’, so regardless of the inspection data, the sketch is rotated so that it looks the same as it does on a DXF plan or similar.

Let’s consider the same manhole again 4 times with different radial references:

What happens to the data values if we rotate the images to face ‘North Up’ in all cases?

The answer is - nothing!

When we rotate the manhole to ‘North Up’, there are no changes at all to any of the clock position values. All that happens is we rotate the sketch, and as you can see, all 4 manholes now look the same, which is no surprise because we defined that from the very beginning.

Also, the user is still standing in the same place relative to the outgoing pipe that they were in the previous image.

Printing

A final comment on printing - the node 2D graph will print the same as it looks in VX, so whatever data has been entered into the inspection details and whatever options (in the future) the user has set in VX will be reflected in their node 2D sketch.

Supporting Documents

This attached file includes the values and images used here:

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