A north arrow shows which way north lies on a plan. On a site plan it normally points to true north, the direction of the geographic North Pole, or to the grid north of the survey. On floor plans it often points to project north instead: a "north" chosen so the building sits square on the sheet. When a set uses both, a good drawing shows both arrows, labelled TN and PN, with the angle between them. Magnetic north, the direction a compass shows, is a third north and is rarely used on construction drawings, because it moves a little every year.
True north, grid north, magnetic north and project north
| North | What it is | Where you meet it |
|---|---|---|
| True north | Along the lines of longitude, towards the geographic North Pole. It does not change. | Site plans, sun and shadow studies, solar orientation |
| Grid north | The direction of the vertical grid lines of a map projection, such as the British National Grid or a US State Plane zone. It differs from true north by the grid convergence, up to a few degrees, and is zero only on the projection's central meridian. | Survey drawings, topographic surveys, GIS data, plans tied to survey coordinates |
| Magnetic north | Where a compass needle points. It differs from true north by the magnetic declination, which changes every year. | Old surveys, field checks with a compass or a phone |
| Project north (plan north) | A direction chosen for drawing. In Autodesk's words, project north "orients the predominant axis of the building geometry with the top of the drawing area". | Floor plans, ceiling plans, enlarged plans |
Ordnance Survey notes that in Great Britain true, grid and magnetic north lined up over the country for a few years from 2022, a line that reached Fraserburgh in north-east Scotland around July 2026 and will not return for at least a few hundred years. Elsewhere, and in Britain from now on, they generally differ.
Why floor plans use project north
Few buildings face exactly north. If every floor plan were drawn to true north, a building turned 23° would sit at an angle on every sheet: walls would not run parallel to the sheet edges, plans would need larger sheets, and dimensions would be harder to read. So the design team picks the main axis of the building as project north and draws all plans square to it. Autodesk's Revit help puts it plainly: plan views "may be oriented to Project North to simplify the design process", while sun and shadow studies use true north.
The cost of this convenience is that the reader has to know which north a sheet shows. That is the job of the north arrow.
Which sheets need a north arrow?
- Site plans and site-related sheets: always. Many planning and permit authorities require it. The City of Cleveland's residential site plan example asks for a "North Arrow (must be at top)" together with a graphic scale; San Diego's Information Bulletin 122 asks for a north arrow on both the site plan and the vicinity map; Madera County, Marion County (Oregon) and Norman (Oklahoma) have similar checklist items. Check your own authority's submission checklist.
- Floor plans, roof plans, reflected ceiling plans, enlarged plans: yes, so the plan can be related to the site.
- Sections and elevations: no arrow. They are named by the direction they face instead (for example "North Elevation"), which only works if everyone agrees which north was meant.
- Details: usually not, unless the orientation matters to the detail.
Ordnance Survey's cartography guidance adds a useful rule for maps: an arrow can be left out of a large-scale map when north is at the top, but it is needed whenever north is not at the top. On a construction set it is simpler to show it on every plan.
Where to put it and how it should look
Conventions vary by office and country. A common one, used in CAD standards based on the US National CAD Standard (for example the Fort Wayne City Utilities CADD standard), is to place the north arrow in the upper right of the view it applies to, rotated to the drawing's orientation, with the graphic bar scale directly below it. Ordnance Survey's advice for maps applies to drawings too: keep the arrow small, simple and subtle. In our view an ornate compass rose adds nothing a reader of a construction drawing needs.
When the plan is drawn to project north, show both arrows: PN pointing straight up the sheet, TN at the true angle, with the angle written next to them (for example "TN 23° E of PN"). Keep the same project north on every plan in the set. A plan rotated differently from its neighbours, without a note, is one of the easiest ways to send a contractor in the wrong direction.
How to set north in Revit, ArchiCAD and AutoCAD
Revit
Revit stores the angle to true north with the project's site (its shared location), and both norths start aligned with the top of the screen. To set true north, open a site plan, set its Orientation property to True North, then use Manage tab, Project Location panel, Position, Rotate True North. Type the angle in Angle from Project to True North on the Options Bar, or drag the rotation control. Each plan view's Orientation property then decides whether that view shows project north or true north. Rotate Project North, in the same menu, turns the model on the sheet without changing true north, which is the usual way to fit a plan to a sheet while keeping the real orientation for sun studies.
ArchiCAD
Watch the terms: what ArchiCAD calls Project North is the real north direction of the model, the one that drives the sun. It corresponds to what Revit calls true north, not to the drawing-convenience north described above. Enter the real north angle there, never a value chosen to make plans fit the sheet. In Archicad 25 and later, set it in Options, Project Preferences, Location Settings by entering the azimuth (versions up to 24 call this panel Project Location), or graphically with Options, Project Preferences, Set Project North (also from the right-click menu of the project name in the Navigator, with a floor plan or 3D window open). The library North Symbol follows project north only when its Follow Project North option is ticked. ArchiCAD also uses project north for the sun position and the Energy Evaluation, so a wrong value shows up in more than the arrow.
AutoCAD
AutoCAD stores a geographic location with the GEOGRAPHICLOCATION command (Insert tab, Location panel, Set Location, from a map or a file). The north direction is an angle from the X axis of the world coordinate system, +Y by default, and can be typed or picked with two points. AutoCAD Architecture adds north arrow tools as annotative blocks. In plain AutoCAD the arrow is usually a block your office keeps, and nothing ties it to the drawing's real orientation: that check is up to you.
How to read north on a PDF drawing set
- Find the arrow on the site plan first. It should be true north or survey grid north. If the survey states which (for example a State Plane zone or a national grid), note it.
- Check it against something independent. Property line bearings such as "N 12°30' E" on the boundary are written relative to the survey's north, so the arrow must agree with them. An aerial image or a map of the street works as a rough check.
- Look at the floor plans. If their arrow points straight up and is labelled PN, they are drawn to project north. The angle between PN and TN on the plans must match the rotation of the building on the site plan.
- Name the elevations yourself. Before you trust "North Elevation", confirm which face of the building it shows on the site plan. If elevations were named by project north, the "north" face may face north-east.
- Watch the revisions. If a later revision rotates the building on the site, every arrow and every elevation name must change with it.
Common mistakes
- The view was rotated, but the arrow was not (in ArchiCAD this happens when the North Symbol's Follow Project North option is off).
- A north arrow block copied from a previous project, pointing the old project's way.
- A true north taken from a phone compass, without correcting for magnetic declination.
- Different project north on different plans of the same set.
- Rotating true north in Revit, or project north in ArchiCAD, when only the plan's fit on the sheet should have changed, which quietly breaks every sun study.
A wrong arrow is worse than no arrow: people trust it.
How far off is magnetic north?
Magnetic declination for 22 October 2026, from the US NOAA calculator (World Magnetic Model 2025):
| City | Declination | Change per year (+ = towards east) |
|---|---|---|
| London | 1.21° east | +0.17° |
| Berlin | 5.19° east | +0.14° |
| New York | 12.46° west | +0.04° |
| Los Angeles | 11.34° east | -0.08° |
| Sydney | 12.83° east | +0.02° |
In New York a compass points more than 12° away from true north. A plan oriented with a phone compass there would be visibly wrong on the site. Look up your own location in the NOAA calculator, and remember that the value is only correct for the date you looked it up.
Frequently asked questions
What is the difference between true north and project north?
True north is the real direction of the North Pole. Project north is the direction a design team chooses so that the building is drawn square on the sheet. Site plans normally show true north; floor plans often show project north.
Which way should a north arrow point?
Towards the north it represents. On a site plan many authorities want north at the top of the sheet. On a plan drawn to project north, the PN arrow points up and the TN arrow points to true north at the stated angle.
Do floor plans need a north arrow?
Yes, so that every plan can be related to the site. Sections and elevations do not; they are named by the direction they face.
Does a site plan need a north arrow?
Yes. Permit authorities commonly list it as a required item, usually together with a scale.
Is magnetic north used on construction drawings?
Rarely. It changes every year, so drawings use true north or survey grid north. If a compass reading is used on site, correct it for the local declination first.
Ncored is the desktop PDF editor we built in our architecture studio for reading and marking up drawing sets from AutoCAD, Revit, and ArchiCAD, on Windows and Mac (Apple Silicon). Large sets stay smooth to zoom and pan, so you can move between the site plan and each floor plan to check that the arrows agree, then mark the question with a revision cloud and a comment right on the sheet. Markups are saved as standard PDF annotations that open in any PDF program. 14 days free. No signup, no email, nothing to enter.
Related: architectural drawing symbols, architectural scales explained, the title block.
All product names, logos and brands mentioned on this page are trademarks or registered trademarks of their respective owners and are used for identification only. Ncored is an independent product by Noir architects and is not affiliated with, sponsored by, or endorsed by any of the companies or organisations mentioned. Software menu names are from each vendor's help for recent versions and can change between releases. Declination values from the NOAA calculator on 22 October 2026. Individual experiences may vary.