Solar guide · Annotated diagram

How to Read a Sun Path Diagram

Learn how time, solar azimuth, altitude, horizon crossings, and seasonal curves fit together in a practical sun path diagram.

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A sun path diagram compresses a moving three-dimensional relationship into a readable daily curve. The horizontal question is direction: where around the compass is the Sun? The vertical question is height: how far above or below the horizon is it? A useful reading always joins those two angles to a local date and time.

The most common mistake is to read a point on the curve as a promise of visible sunlight. The point describes solar geometry. A hill, neighbouring building, tree canopy, cloud layer, or window reveal can still remove the direct beam. Treat the diagram as the unobstructed sky baseline against which real conditions are checked.

Start with the coordinate system

Solar Path Tracker reports azimuth clockwise from true north. North is 0°, east is 90°, south is 180°, and west is 270°. An azimuth of 72° therefore places the Sun east-north-east, not 72° above the horizon.

Altitude is a separate angle. Zero degrees is the astronomical horizon, positive values are above it, and negative values are below it. A 15° altitude indicates shallow light and usually long shadows; a 70° altitude indicates a high Sun and shorter shadows on level ground.

Follow one date from left to right

Read the local-time labels in sequence rather than comparing disconnected points. Before sunrise the altitude is negative. It crosses the horizon near sunrise, rises to a daily maximum around solar noon, then falls through sunset. Clock noon and solar noon are not guaranteed to coincide because longitude, timezone boundaries, and daylight-saving rules affect the displayed clock.

The azimuth curve should be read at the same timestamp as the altitude curve. This pairing tells you both which side of a site faces the Sun and how steeply the direct rays arrive.

Annotated diagram

Brisbane equinox sun-path diagram dataset

This original diagram plots seven fixed Brisbane readings on 23 September 2026. Every labelled point has the same time, azimuth, and altitude in the table and downloadable CSV, so the visual can be checked without estimating from pixels.

Brisbane equinox solar altitude and azimuth pointsA time-based curve rises from near the horizon in the morning to its highest altitude near noon and returns toward the horizon by evening. Each point is labelled with time and azimuth.0°20°40°60°80°Astronomical horizon06:00Az 88°08:00Az 72°10:00Az 45°12:00Az 350°14:00Az 304°16:00Az 282°18:00Az 268°Local time · Australia/Brisbane
Altitude controls vertical position; the azimuth label identifies the compass bearing at the same timestamp. This is an unobstructed astronomical path, not a visible-horizon survey.
Text alternative for every plotted Brisbane equinox point
Local timeAzimuthAltitudeState
06:0087.6° East4.1°golden
08:0072.0° East30.3°day
10:0045.4° North-east53.2°day
12:00349.8° North62.0°day
14:00303.7° North-west46.7°day
16:00282.3° West22.1°day
18:00267.8° West-4.3°night

Download the evidence dataset

The plotted Brisbane equinox points shown in the original diagram and accessible data table. The UTF-8 CSV uses a fixed column order and contains calculated values only.

Turn the chart into a site observation

Choose the date and hour that match the decision, note azimuth and altitude, then stand or orient a plan toward that bearing. Check whether the real horizon is clear. If an obstacle is present, estimate or measure its angular height and compare it with the solar altitude.

Repeat the observation for a winter and summer date. One day can answer a scheduling question; two seasonal references reveal whether a facade, courtyard, or outdoor workspace behaves differently across the year.

  • Pair azimuth and altitude from the same timestamp.
  • Use exact event tools for sunrise, sunset, and golden-hour boundaries.
  • Verify true-north orientation and local obstructions before a consequential decision.

Responsible use

Practical uses and model limits

Useful for

  • Comparing morning and afternoon exposure before a property inspection.
  • Selecting useful observation times for a shading or facade survey.
  • Planning a photography angle around a known compass direction.

Do not overlook

  • The diagram does not include terrain, buildings, trees, cloud, haze, or window geometry.
  • Hourly samples are not substitutes for exact event timestamps between whole hours.
  • A magnetic compass can differ from true north; account for local magnetic declination when measuring on site.

Sources and reproducibility

Evidence and calculation sources

  • NREL Solar Position Algorithm report

    Independent reference for solar-position inputs and angular conventions; NREL does not endorse this site.

  • SunCalc

    Solar position and astronomical event calculations used by this site.

  • Luxon

    IANA timezone-aware conversion between the selected local time and UTC.

  • Solar Path Tracker methodology

    Definitions, angle normalization, polar handling, precision, and model limits.