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Measurements

During the inclination test, WinCan VX takes only 2 values from the camera:

• The distance measurement (in metres or feet)

• The attitude (in percent)

Everything that is then printed and reported is calculated from these two columns of data. The data points are read and recorded by WinCan VX every time there is a change in the attitude value, and due to the hyper sensitivity of the inclinometer, this means that a lot of points are recorded.

Having already described the value of 100% attitude as a 45 degree slope, the cameras available on the market are not capable of measuring this value. If you take a CCTV camera in your hand and watch the inclination value on the screen from the device and try to get it level and reading zero, then slowly tip the camera nose up (or down) and you will see that the inclination hits a maximum value of about 23% depending on the manufacturer and will not go any further.

This attitude value of 23% equates to an angle of approximately 13 degrees, so the maximum and minimum gradients that the device can measure are not very far away from a perfectly flat line.

Data Basics

In order for an inclination test to show that a pipe flows nicely downhill, we would expect there to be more negative values in the data points than positive values if the test was done from the upstream end. In other words, the average attitude value over the length of the test will be negative, and the delta height will also be negative.

But, what happens if we test exactly the same pipe with the same camera on the same day from the other end, the downstream end. Now, the majority of the measurement points will be positive, the average attitude value will be positive and the delta height will be positive.

So, we have two tests of the pipe where one says the average gradient is +2% and the other says it is -2% so which one is correct?

Well, they are both correct, bu this is confusing to engineers and operators trying to understand the data, because this idea is utilising an old concept of ‘start’ and ‘finish’ manholes which has now been abandoned by most global CCTV inspection standards. In other words, it relates the data from where the camera was inserted into the pipe (i.e. the upstream or downstream end).

In most drainage standards now we have moved to the more intuitive concept of upstream and downstream manholes instead of start and finish manholes.

WinCan VX uses this concept in all inclination graphs so that the upstream end of the pipe is always on the left side of the graph and the downstream end is always on the right side, regardless of which way the test was done, so that in all cases a happy drain goes downhill on the chart from left to right.