Cymap - Which Direction is North?

by Gary Mann

Often when you receive a DXF file the North Arrow, by convention, is clear of the Building of interest. Whilst this is fine for a printed output, if the North arrow is remote from the building in a digital Model it will often result in one of the following:

1. The North arrow will not be included with the DXF layout or

2. The drawing extents will be larger than needed resulting in unnecessary zooming and reduced accuracy.

Including the North Arrow on any one of the floorplans will enable the orientation to be directly compared to the Cymap “Info Box.” Even if the proposed work only includes PH or Piping input you cannot guarantee that the scope will not change during the project lifespan and Solar considerations will later be required.Note the BRE  iSBEM Tutorial project above contained within the Cymap Tutorial Projects has the North Arrow inside the building. Placing to the left or the right would be fine, as there is space in this project layout, but placing the N arrow above or below the building would reduce the clarity of the Home View.

Because the Arrow is pointing directly up, guessing the angle is relatively easy. If you have a project where the North Arrow points in a non-orthogonal direction, do you estimate the angle by “eye” and correct by trial and error? Few of us have natural “Pool Table Geometry” skills, so there is a much simpler method involving our trusty “Ortho Angle” utility.

1. Click on the North Arrow displayed in the Info Box.

2. This will initiate the “Orthogonal Angle utility”. You will be advised to Click on a Start and Finish Point. Use any point on the DXF North Arrow and draw the line through the Arrow or parallel for as long as possible to maximise the accuracy. Use “Display>Options>Ortho Lines>Angle and note that the angle set is 16 degrees to the horizontal. Reset the Ortho Angle to zero by editing the text box.Then, in Building>Edit>General, enter 270 + 16 = 286 in the orientation text box.Finally, you can see that both North arrows (DXF & Info Box) are pointing in the same direction and as such is a good Quality Assurance check on your own and other’s projects.

If you found the number 286 made you nostalgic for an old friendly computer, please send feedback or suggestions to gary.mann@cadline.co.uk