How is the shadow length calculated?

Shadow length equals the object's height divided by the tangent of the sun's altitude angle: L = H ÷ tan(altitude). As the sun gets lower in the sky, the tangent shrinks and the shadow grows longer — at a very low sun the shadow can be many times the object's height.

What does "sun azimuth" mean?

Azimuth is the compass direction the sun is in, measured in degrees clockwise from true north (0° = north, 90° = east, 180° = south, 270° = west). The shadow always falls in the opposite direction, at azimuth + 180°.

Why does the sidebar say the sun is below the horizon?

This happens at night, or before sunrise / after sunset for the date and location you've selected. No shadow is cast when the sun's altitude is 0° or below, so the shadow fields are left blank in that case.

Is this tool free, and where does the sun position data come from?

Yes, completely free — sun altitude, azimuth, sunrise and sunset are calculated locally in your browser using SunCalc, an open-source astronomical library based on well-established solar position formulas. Nothing about your location or timing is sent to a server.

How accurate is the shadow length?

The sun position itself is accurate to within about a minute of arc for any date between roughly 2000 and 2100. The shadow length assumes flat, level ground around the object — a shadow falling across a slope, or over other buildings, will differ from the flat-ground estimate shown here.

Can I calculate a shadow for a future date, like next winter?

Yes. The date picker accepts any date — past, present, or years into the future — since the sun's path depends only on the date and the site's latitude/longitude, not on the current year.

What happens near the Arctic or Antarctic Circle in summer or winter?

At high latitudes the sun can stay above the horizon all day (midnight sun) or never rise at all (polar night) around the solstices. Sunrise and sunset show as "—" in those cases, since there isn't a single rise or set event that day.

Does the tool account for terrain, trees, or nearby buildings?

No. It calculates the geometric shadow of a single object of the height you enter, standing on flat, open ground. It doesn't know about hills, other structures, or vegetation that might block or extend the shadow further in reality.

What's the difference between the sun-direction line and the shadow-direction line on the map?

The short amber line always points toward the sun's actual compass direction (azimuth). The longer orange dashed line points the opposite way, scaled to roughly match the shadow's real length (capped for readability on the map), showing where the shadow physically falls.

Can I download the result?

Yes. "Download GeoJSON" saves the location plus both direction lines as a standard GeoJSON file with the sun altitude, azimuth, shadow length and direction as properties. "Download PDF Report" generates a printable summary including the diagram, ready to save or share.

Why is my shadow length showing a very large number?

That's expected close to sunrise or sunset, when the sun's altitude is only a degree or two above the horizon — the tangent of a very small angle is tiny, so height ÷ tangent produces a very long shadow, exactly as it does in reality at those times of day.

Does the time use my local time zone or the selected location's?

The location's. When you pick a point, the tool automatically looks up its time zone, so "14:00" always means 2 PM at that pin — not 2 PM on your own device — even if you're checking a spot on the other side of the world. Sunrise and sunset are shown in that same local time.

Solar Shadow Calculator — Shadow Length, Direction & Sun Position | OnlineMapMaker

Click any point on the map, set a date, time and object height, and see the sun's altitude and azimuth, sunrise and sunset, and the resulting shadow length and direction — drawn on the map and in a live diagram. Export the result as GeoJSON or a PDF report. Open in full screen ↗

What This Tool Calculates

Every object under the sun casts a shadow whose length and direction depend entirely on where the sun is in the sky at that exact moment — its altitude (height above the horizon) and azimuth (compass direction). This tool calculates both precisely for any location, date and time you choose, then works out the length and direction of the shadow cast by an object of the height you enter, showing the result on the map and in a side-view diagram.

The Shadow Length Formula

Shadow length follows straightforward right-triangle trigonometry: the object, its shadow, and the sun's ray form a triangle where the object's height is the opposite side and the shadow is the adjacent side, with the sun's altitude as the angle between the shadow and the ray. That gives shadow length = height ÷ tan(altitude) — a low sun (small altitude) produces a long shadow, and a high sun (large altitude) produces a short one:

Sun altitude: how high the sun sits above the horizon, in degrees — 0° at the horizon, up to 90° directly overhead. This is the angle used in the shadow formula.
Sun azimuth: the compass direction the sun is in, measured in degrees clockwise from true north. A shadow always falls in the exact opposite direction — azimuth + 180°.
Object height: the height of the pole, building, panel or person casting the shadow, in meters. Doubling the height doubles the shadow length at any given sun angle.

Reading the Sun & Shadow Diagram

The diagram panel draws two views side by side. The left side view shows the object as a vertical line, the sun's ray as a dashed line down to the ground, and the shadow as a solid line along the ground, with the altitude angle marked where the ray meets the ground. The right compass view shows the sun's azimuth as an amber line and the shadow's direction as an orange dashed line, both measured from true north.

Exporting Your Result

Click "Download GeoJSON" to save the clicked location plus the sun-direction and shadow-direction lines as a GeoJSON FeatureCollection, with the altitude, azimuth, shadow length and direction stored as properties on each feature. Click "Download PDF Report" for a printable summary of the location, date and time, sun position, and shadow result, with the diagram included as an image.

Step by Step

Step 1

Open the tool

The map opens on New York by default with the current date and midday local time already calculated. The sidebar shows sun position, sunrise/sunset, and shadow results immediately.

Step 2

Pick a location

Click anywhere on the map, search for an address or place name, type raw lat,lng coordinates, or click the location icon to use your current GPS position.

Step 3

Set the date

Choose any date, past or future — the sun's position is calculated exactly for that day, so you can check a shadow study for any season.

Step 4

Set the local time

Choose a time of day. Earlier and later times give a lower sun altitude and a longer shadow; midday gives the shortest shadow of the day.

Step 5

Enter the object height

Type the height in meters of the pole, building, tree, or structure casting the shadow. The shadow length recalculates instantly.

Step 6

Read the sun position

The sidebar shows sun altitude (height above the horizon) and azimuth (compass direction), plus sunrise and sunset times for that date and location.

Step 7

Read the shadow length and direction

If the sun is above the horizon, the sidebar shows the shadow's length in meters and its compass direction — always the opposite direction from the sun.

Step 8

Check the map and diagram

An amber line on the map points toward the sun; an orange dashed line shows the shadow's direction and approximate length. The diagram panel shows a side-view of the angle and a compass top-view.

Step 9

Export your result

Click "Download GeoJSON" to save the location and both direction lines as a GeoJSON file, or "Download PDF Report" for a printable summary with the diagram included.

Real-World Use Cases

🏗️

Solar Panel Shading Studies

Installers check whether a nearby tree or building will cast a shadow across a proposed panel array at different times of year before committing to a design.

☀️

Construction & Planning Shadow Studies

Architects and planners estimate how a proposed building's shadow will fall on neighboring properties, streets, or parks at specific times of day and year.

📐

Photography & Film Location Scouting

Photographers and cinematographers check exactly when and where shadows will fall at a shooting location, for golden-hour timing or avoiding unwanted shade.

🌳

Garden & Landscaping Planning

Gardeners work out how much shade a fence, tree, or building will cast over a planting bed through the seasons before deciding what to plant where.

📸

Sundial & Outdoor Design

Designers of sundials, outdoor art, or shade structures use the sun's real azimuth and altitude at a site to size and orient their design correctly.

🏙️

Real Estate & Property Assessment

Buyers and agents check how much a neighboring building shades a property's yard or windows at different times of day before making a decision.

🎬

Event & Outdoor Venue Planning

Event planners check where shade will fall across a venue at the exact time of an outdoor wedding, market, or festival.

🎓

GIS & Solar Education

Students and GIS learners use the live diagram to build an intuitive feel for how sun altitude and azimuth relate to shadow length and direction.

Common Questions

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Map tiles © OpenStreetMap contributors and CARTO, Esri (satellite & terrain). Sun position, sunrise and sunset calculated with SunCalc. Address search and location lookup by OpenStreetMap Nominatim. All shadow geometry is calculated locally — no location or timing data is stored on any server.

Solar Shadow Calculator — Shadow Length, Direction & Sun Position on a Map