Finding North

Henry Ford once said, ‘The only real mistake is the one from which we learn nothing.’ This article, Finding North, is a tale of how a simple oversight in understanding north can have devastating consequences.

The background

The story begins some 20 years ago when a recent architectural graduate was working on a multi-residential project. There was nothing particularly out of the ordinary about the project apart from its beachfront location. Yet the size and bulk of the project were sure to raise eyebrows from the local council. And sure enough, it did. The Development Application was rejected. A furious client seeking to challenge the decision took the matter to the Planning and Environment Court. 

With expensive, hourly-rate barristers on both sides, the arguments were intense. The local council argued that the building was too tall and overshadowed the beachfront and public space below. Like most responsible architects, however, a survey had been commissioned from a licenced surveyor, and they were adamant in the accuracy of their overshadowing analysis. Expert witnesses were called one-by-one to testify on everything from the building’s visual impact, through to the validity of the council’s overshadowing map. But what emerged from this process was that the architect had used the wrong north in their overshadowing analysis and the building was overshadowing. Wrong north? Surely north is north. Well no, and this oversight became a significant factor in the council winning the case. 

North is not always North

So how could this oversight have happened? The answer is simple; to perform solar access and overshadowing analyses, we need to calculate the sun path, which references true north, not the Map Grid of Australia (MGA). But many architects confuse the two, and it is not hard to see why.

MGA is the projected coordinate system used in Australia. As explained in this tutorial, MGA is a flat, two-dimensional surface. Gridlines are straight and parallel. But as we’ve known since the 5th century BC, the earth is not flat. True north is the direction along the earth’s surface towards the geographic North Pole. MGA is, therefore, grid north and differs from true north. The angle between grid north and true north is known as the grid convergence, and in Sydney, true north is west of grid north by almost 1 degree.

Confusion, therefore, arises firstly due to the fact of dealing with two norths (grid north and true north), and secondly where there are mixed requirements for Development Application whereby some drawings/models need to be orientated to MGA, while others need to be orientated to true north. To demonstrate this, take Clause 6.17 of Sydney’s Local Environment Plan (LEP) 2012, which describes sun access planes: “coordinates are Map Grid of Australia 1994 coordinates and horizontal bearings are measured from true north.” Moreover, while MGA is often defined, true north and grid convergence are not, presumably because they are accepted concepts in geodesy. In any case, much confusion could be avoided if a simple definition was added to the relevant documents.

Lessons learnt

The lesson for anyone dealing with this topic is simple; ensure you are crystal clear about coordinates and orientations. Seek clarification from your surveyor and local council where required. And above all, ensure that staff running your solar or overshadowing analyses are doing it correctly. It may just save you a trip to the courtroom.

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