Alignment

The Alignment pane lets you align events in one workpack with events in another. If you have carried out multiple inspections on an asset with KP (such as a pipeline), survey may have been calibrated differently in different years. Thus, the same physical object may be logged at slightly different KPs in different inspections. This tool lets you bring all those subtly different KP measurements into alignment with each other.

Ensure that the events that you want to align on are visible in the Event Listing, by setting filters as required. Choose a baseline workpack and an alignment workpack using the toolbar buttons.

You will see a chart showing events from both workpacks, with the ‘Provide Suggested Control Points’ pane at the right. This pane lists the event types that NEXUS IC believes might be suitable for matching on — essentially, events that have KP. Each event type has a checkbox and a slider. If you check the box next to a given event type, NEXUS IC will suggest control points, in that event type’s colour. The slider at the right of each event type controls sensitivity: if the slider is all the way to the left, it will only suggest pairs of events that have identical KP. As you move the slider to the right, it will suggest points that have more and more KP difference, up to a maximum of 25 metres. The default slider position is 5 metres.

Check one or more event types. Good choices are event types that represent static objects: pipeline features, anodes, field joints, etc. Bad choices are event types that represent thing that might change location over time: freespans, burials, etc. Adjust sliders as required: if the survey variation from one workpack to the other is more than 5 metres, you will need to adjust sliders upwards.

NEXUS IC should now display some suggestions. These are only suggestions — as yet, no links have been made. To convert a suggestion into a link, zoom in on the chart (put the mouse over the KP axis and spin the mouse wheel, or adjust the zoom bar at the bottom of the pane) far enough that you can select that individual point, click on the point to select it, and click Link.

You can also make a link that is not based on a suggestion — for example, suppose that a particular object has been logged one year as a Feature and the next year as a Survey Note. NEXUS IC will not automatically suggest a link if the event types are different, but you can still manually click those two events and click Link.

If you change your mind, you can click Unlink to unlink a single pair of events, or Unlink All to start again from scratch.

Once you are happy with the links you have made, click Align. NEXUS IC will then align events between the lowest and highest KPs you have created links for. Adjustments will be made to the KPs of events in the Alignment Workpack. This may take some time, depending on the number of events involved. (If you are carrying out a test, you may wish to do so on a small KP range.)

Events will be adjusted based on the Linked points nearest them: for example, if you have a point at KP 0 linked to a point at KP 0.004, and another point at KP 1 linked to a point at KP 1.004, all points in the Alignment Workpack between KP 0.004 and KP 1.004 will have their KP decreased by 0.004 km. If your low points were at KP 0 and KP 0.004 and your high points were at KP 1 and KP 1.008, then weighted scaling would occur: a point halfway between at KP 0.506 would have a scaling halfway between 0.004 and 0.008 (i.e. 0.006) applied; a point at KP 0.252 would have a scaling of 0.005 applied, and so on.