Sun hours map

The sun hours map computes how many hours of direct sun each point on the ground receives on the chosen date and gives it as a plate and three values.

Updated 15 October 2026This page was written by AI.

Overview

The «3D model» on the «Sun & shadow» tab shows the shadow at one time of day. The sun hours map solves the shadow every 10 minutes from sunrise to sunset and adds up, at each point on the ground, the time in sun. The same calculation appears as the SUN HOURS plate in the diagram set (winter solstice).

SUN HOURS plate, Stadsdriehoek, Rotterdam, winter solstice: streets and squares in dark blue, buildings in pale grey — SUN HOURS plate (Stadsdriehoek, Rotterdam, 500 m radius, winter solstice, detail). Dark blue is under 1 hour of sun; buildings are pale grey

How to use

Set the site and the radius
On the «Sun & shadow» tab, choose the sun hours map
Choose the date (21 June, 21 March, 23 September or 21 December)
Start the calculation
Save with «Save PNG» or «Save plate only»

Values on the sheet

Value	Definition
Daylight	Time from sunrise to sunset on the chosen date
Mean sun hours	Mean daily sun hours on the ground inside the plate
Under 1 h	Share of the ground that receives less than 1 hour of sun in the day

The values compare positions. They are not a planning criterion; no Dutch sunlight criterion is applied.

Time reference

The map sums the whole day from sunrise to sunset. Times are shown in standard time (CET, UTC+1) without summer time. In Delft (4.37° E) the sun is due south between about 12:26 and 12:57 CET through the year, because the site lies west of the 15° E meridian of the time zone and the equation of time shifts noon by up to about ±16 minutes.

Method

The map uses the same building height map as the wind and thermal comfort sheets (3DBAG heights on BAG outlines), plus the AHN4 terrain. Shadow is pure geometry.

For the chosen date, the sun position is computed every 10 minutes from sunrise to sunset
At each step, every ground cell is classed as in sun or in shade
The time in sun is summed for each cell

Radius	Compute time
300 m	about 4 s
500 m	about 14 s
800 m	about 28 s

Display

Colour breaks are at 0, 1, 2, 3, 4, 5, 6, 8, 10 and 12 h. Up to 6 h the bands are 1 hour wide. Buildings are filled pale grey.

Limitations

Indicative simulation, not a regulatory assessment. The plate does not replace a sunlight study made with measured data and validated software.

Buildings finished after 2022 may have no 3DBAG height and cast no shadow or a short one, so those spots can read sunnier than reality
The plate measures sun on the ground. Windows are vertical and differ by floor; the value on the ground says nothing about the rooms above it
Trees are not included. Tree shade is used only on the thermal comfort sheet

Data sources

Data	Use
BAG outlines (Kadaster, CC0) · © 3DBAG by tudelft3d and 3DGI (CC BY 4.0)	Building height map
AHN4 (CC0)	Terrain

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