How accurate is the solar position calculation?

The simulator uses the NOAA/Spencer algorithm, which provides an accuracy of approximately ±0.5° for the years 1950 to 2050.

What is the difference between UTC and local solar time?

UTC uses standard clock time adjusted by your timezone offset, while local solar time calculates the sun's position based strictly on your longitude, ignoring time zones and daylight saving time.

How is the shadow direction determined?

The shadow direction is calculated as the antipode (opposite angle) of the sun's azimuth, indicating where the shadow tip falls relative to the object's base.

Does the simulator account for atmospheric refraction?

Yes, it includes NOAA's piecewise atmospheric-refraction correction, which ensures high accuracy even when the sun is near the horizon.

Can this tool detect polar nights or midnight sun?

Yes, the algorithm automatically detects and displays polar night and midnight sun conditions based on the input latitude and date.

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Astronomy

Sun Position & Shadow Length Simulator

Compute the sun’s elevation and azimuth (NOAA algorithm) for any latitude, longitude, date and time, plus the length and direction of the shadow cast by an object of a given height, with sunrise/sunset and a full-day shadow curve

Details

What this tool helps you do

Enter latitude, longitude, a date/time and the height of an object (a pole, a building, a tree), and the tool computes:

Sun elevation (altitude above the horizon) and azimuth (compass bearing, 0=N, 90=E) using the NOAA/Spencer solar position algorithm.
Shadow length on the ground = object height ÷ tan(elevation), shown both in absolute units and as a multiple of the object height.
Shadow direction (the antipode of the sun azimuth — where the shadow tip falls from the object's base).
Sunrise / solar noon / sunset in local standard time, including polar-night / midnight-sun detection.
A full-day curve of elevation and shadow length, with the selected moment marked, and a top-down shadow plan showing the object, sun ray, and cast shadow.

Algorithm details:

Solar declination via Spencer's series; equation of time via the NOAA 3-term approximation.
Apparent elevation includes NOAA's piecewise atmospheric-refraction correction (accurate near the horizon).
You can choose UTC (input time treated as UTC), or local solar time (time-of-day at the longitude, ignoring time-zone and DST — handy for a "where is the sun at 10am solar time" answer).

Accuracy is ~±0.5° in elevation/azimuth for years 1950–2050 — ideal for solar panel siting, architectural shadow studies, gardening, photography planning, or film/game level design.

Execution

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Fill in the form, run the tool, and review the result in one place.

Prepared example runs

Click an example to fill the form automatically. File inputs still need an upload.

1 examples

Summer-solstice noon shadow in New York

1.8 m person at 40.71°N, 74.01°W at local solar noon on the 2026 June solstice — expect a short shadow of about 0.56 m pointing almost due north.

<div>Elevation ≈ 72.7°, azimuth ≈ 180.0°, shadow ≈ 0.56 m toward true north; sunrise ≈ 04:27 and sunset ≈ 19:32.</div>

Inputs

Set the required fields, then run the tool.

7 options

SettingsAdjust formats, ranges, numbers, and modes.7

Latitude (°)numberRequiredLongitude (°)numberRequiredDatedateRequiredHour of day (0–24, fractional allowed)numberOptionalObject height (m)numberRequiredTime zone offset (hours from UTC)numberOptionalTime zoneselectOptional

Result

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Samples

Sun Position & Shadow Length Simulator

What this tool helps you do

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Prepared example runs

Inputs

Result

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Key facts

Overview

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How it works

Use cases

Examples

1. Summer Solstice Shadow Analysis in New York

2. Winter Shadow Projection for a London Building

FAQ

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