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HADDMS Node Referencing

In HADDMS data projects, we are always offered to fields where there can be a continuous, point or region asset reference. In the shapefiles these are:

• PIPE_REFER - in the continuous shapefile for the HADDMS system reference.

• ASSET_REF - in the point and region shapefiles for the HADDMS system reference.

• SUPP_REF (in all cases - the user’s own reference for the asset).

This page is an information page for how the HADDMS system references work, and you should not use this naming style for the SUPP_REF wherever possible, because the HADDMS validator will complain if the 2 references are the same at the point of upload of the final data.

It is common when working with HADDMS asset records to see system manhole references like NZ2456_7348a (made up example) and although this seems like a mad set of numbers and letters, the way these are constructed is actually quite simple.

The numeric part of this represents a 10m square grid on the ground by GIS coordinates and the letter at the end is an incremental counter starting at a, so a is the first node inside this 10m grid, followed by b, c etc.

To understand this referencing, we must split it up into its 7 constituent parts:

• NZ 24 56 _ 73 48 a

  • NZ = the 100km grid tile as specified by the Ordnance Survey. Remember 100km = 100,000 metres.

  • 24 = the 24th kilometre across the NZ box from the bottom left corner starting at 00.

  • 56 = the 58th kilometre up the NZ box from the bottom left corner starting at 00.

  • _ = fixed text character.

  • 73 = the 73rd 10m segment across the km grid square starting at 00.

  • 48 = the 48th 10m segment up the km grid square starting at 00.

  • a = alpha node counter inside this 10m grid.

     

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From this, we can deduce that the NZ 100km grid tile is in the North East of England, and if we count 24Km East from the bottom-left corner of the tile and 56Km North from the bottom-left corner of the tile, then we hit the red cross:

The red cross is the location of the 1km grid square and then we split this 1Km square up into 10m square tiles to find the 7th square across and the 4th tile up from the bottom left corner.

Using this system we can define the geometric coordinates of every node in the country to within a single 10 x 10 metre square.

Pipe Referencing

The HADDMS inspection standard follows the same PLR Suffix naming convention of Upstream Node plus PLR Suffix as the WRc system, except that it does not X, Y and Z for the PLR Suffix. Instead, it uses a dot and a numeric incremental counter like .1, .2, .3 etc so the MH1X pipe in the diagram above would be MH1.1, MH1Y is MH1.2 and MH1Z is MH1.3.

As an example using the same manhole ID as above, maybe we have 2 pipes running downstream from this node, so their HADDMS system references would normally be:

• NZ2456_7348a.1

• NZ2456_7348a.2

Other than that, the logic is exactly as described in WRc Collecting Good Site CCTV Inspection Data.

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