Saint-Jean-du-Maroni: 125 hectares of the relegation heritage by LiDAR

Background

From 1887 Saint-Jean housed the relegation camp, for repeat offenders sent to French Guiana under the 1885 law. Presented to the regional heritage and architecture commission in October 2023 with a view to listing as a historic monument, the site had to be mapped to set the perimeter of the protected buildings. The culture, youth and sport directorate wanted a terrain model revealing every relief anomaly that might correspond to human-made structures, over 125 contiguous hectares.

What we did

The specifications required at least 25 points per square metre on the ground, 5 cm horizontal and 10 cm vertical accuracy, and an orthophoto of 10 cm per pixel or finer. Acquisition took place from 23 to 25 October 2024. On the first day, rain forced the drone to land twice and the last flight was completed in a downpour: the noise left in the cloud, located at height and away from dense vegetation, was filtered out with no effect on the terrain model. Deliveries ran until 7 November: raw then classified cloud in sixteen tiles, 25 cm terrain and surface models, an A0 greyscale extract of the surface model, a 3 cm orthophoto in three formats and plans by sub-zone.

In the mission log

1. October 2024

   LiDAR and photogrammetryFrench Guiana

   LiDAR survey of 125 hectares of the relegation heritage of Saint-Jean-du-Maroni

   Saint-Jean-du-Maroni · Préfecture de Guyane

   For the regional historic monuments service, from 23 to 25 October 2024: 25 ground points per m² required, 25 cm terrain and surface models, 3 cm orthophoto and a classified cloud in sixteen tiles, delivered by 7 November to delimit the buildings of the former camp to be protected.

   • 125 ha
   • 25 cm terrain model

   Read the article

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