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Now we should look more close at the data option in the top-right quadrant of the panel. For this example, the basic data looks like this:

Inclination data.

What do these values tell us?

The 4 cells with numbers here are in two rows for the start and the end of the test:

At the start of the test, the distance was 0.41 m and the altitude was -2.2 m (this is zero minus the upstream pipe depth from the header because the manhole cover is assumed to be at zero with no other option selected).
At the end of the test, the distance was 22.16 m (hence the test length is 21.75 m and not the pipe length of 23.0 m) and the altitude was -2.29m (this is the new altitude calculated from the measurement points from the starting altitude of -2.2). Notice that the starting altitude plus the delta altitude equals the end altitude (-2.2 +-0.09 = -2.29).

The fact that the distance started at 0.41 and ended at 22.16 tells us that the camera went forwards during the test which we already know, and the fact that the altitude started at -2.2 and ended at -2.29 tells us that the camera went downhill during the test run.

Now, select the ‘Fit to Altitudes’ option:

Fit to Altitudes results.

This option is only available to the user if the altitudes of the ends of the pipe above sea level are available in the section header of the pipe. The ‘Calculate Invert Levels’ button in WinCan VX can be very useful here, but this will only work if the cover levels are defined and the pipe depths are defined in the data.

When ‘Fit to Altitudes’ as active, the graph is stretched or compressed to lock it between the measured GIS data altitude values. This is where the data becomes more meaningful, but can also hide or mask calibration problems with the camera system.

Notice now:

The ‘Delta Altitude’ has changed to -0.22 m, because this is now locked by the header data.
The ‘Measured Inc.’ has changed to -1.03 % because this is now locked by the header data.
The upstream end of the pipe line is at 121.63 m as defined by the data.
The downstream end of the pipe line is at 121.4 m as defined by the data.
The thick blue curve now starts and ends on the thin brown line. This is noticeable because the inclination test length is shorter than the full pipe length, so there are gaps at each end, and we can only assume that in these small zones, the pipe is ‘perfect’. If the inclination test was much closer to zero and 23 m distances then these gaps would still be there, but they would become almost invisible.
In the top right corner, we can now see the altitudes at the top and bottom ends of the pipe, the pipe depths at each end and therefore the manhole cover levels at each end.

This graphical output is generally considered to be the most useful report for engineers, but it relies on some detailed data for the altitude levels in order to be available. It also makes a number of assumptions based on good engineering judgment, so there is always a compromise in presenting this kind of data.

Another advantage of activating the ‘Fit to Altitudes’ option is that if the CCTV inspection was abandoned half way along the pipe due to a problem and the inclination test was carried out, then the thick blue line will be fixed to the pipe and will only draw half way across the graph, so again, it will give an intuitive representation of the data that has been collected.