Information about the "Latitude Lambersart" project.

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latitudeInfo130324 
Information about the "Latitude Lambersart" project.

The aim of the "Latitude Lambersart" art project is to visualise the four seasons in mosaic. 
The concepts of latitude and longitude, the north-south meridian, summer and winter time, Greenwich Mean Time, the equator, the Tropic of Cancer, the Tropic of Capricorn and the tangent, and the 180° compass are used. 
A 100 cm stick casts shade according to date and time, when the sun is at its local zenith.
The reference location in Lambersart is Square Jean-Monnet at the crossroads of Rue du Bourg, with the following geographical data:
- Latitude: 50° 39' 6.3'' ( 50,65175°) - Longitude: 3° 1' 43.602'' ( 3,02877°)
The mosaic has a perimeter of 4 metres by 4 metres. The 4 circles have diameters of 51 cm, 122 cm twice and 350 cm, corresponding respectively to 21 June, 21 March and 21 September, and 21 December 2024. The local meridian determines the time at which the length of the shadow is measured. Generally speaking, the length to the east is deducted from the G.MT., 4 minutes per degree, and 4 minutes per degree are added to the west. For Lambersart 3 X 4 minutes, i.e. 12 minutes, are deducted from the G.M.T. 1 hour is added to the GMT for summer time (29 March 2024 to 27 October 2024) and 2 hours for winter time from 29 October 2023 to 28 March 2024.
So with a 100 cm stick and the compass at 180°, the shadow lengths are as follows:
At 13:48 on 21 March, the shadow was 122 cm; the sun was on the equator.
On 21 June at 12.40pm, the shadow was 51 cm; the sun was in the Tropic of Cancer.
On 21 September at 12:31 pm, the shadow was 122 cm; the sun was on the equator.
On 21 December at 13:37, the shadow was 350 cm; the sun was on the Tropic of Capricorn.
The circles have a corresponding diameter. 
We can say that the shadow length corresponds to the tangent of the latitude:
The tangent of 50.65175° is 1.21966 and represents approximately 122 cm of the shadow.
The tangent of 27.2154° (50.65175 - 23.4363°) is 0.5127 and represents approximately 51 cm of the shadow.
The tangent of 74.0875° (50.65175° + 23.4380°) is 3.5079 and represents approximately 350 cm of the shadow.
On 21 March 2024, an information session will be held at Square Jean-Monnet between 12.30 and 2.30 p.m. The project is one of Lambersart's participatory projects.
Elsewhere, applications need to be adapted to local latitudes and longitudes. Would you like to check the tangent at home and measure the shadow of the church tower on 21 March 2024? Curious