Eaux de surface détectées par satellite à Fada et alentours, Tchad

Name: Eaux de surface détectées par satellite à Fada et alentours, Tchad
Creator: United Nations Satellite Centre (UNOSAT)
License: http://www.opendefinition.org/licenses/cc-by-sa

✦ DISCOVERED BY ORIONAIUnited Nations Satellite Centre (UNOSAT)Imagery and land coverChad

Chad

About this dataset

**UNOSAT code: FL20190827TCD** Cette carte illustre l'étendue des eaux de surface détectées par satellite (Landsat 8, image comprenant des données du 23 au 27 Août 2019) à Fada et alentours. Dans la zone analysée d'environs 20,000 ha,quelques centaines de personnes vivent en proximité des1,500 ha d'eau de surface détectées entre le 23 et le 27 Août2019. Ceci est une analyse préliminaire qui n'a pas été validée sur le terrain. Merci d'envoyer vos commentaires à UNITAR-UNOSAT.

Documentation

UNOSAT datasets and maps are produced using a variety of methods. In general, analysts closely review satellite imagery, often comparing two or more images together, and determine notable changes between the images. For damage assessments, refugee or IDP assessments, and similar analyses, these changes are then manually documented in the vector data by the analyst. For flood extractions, landcover mapping and similar analyses, a variety of automated remote sensing techniques are used to extract the relevant information which is then reviewed and revised as necessary by the analyst. In all cases, resulting data is then loaded into a standardized UNOSAT geodatabase and exported asshapefiles for dissemination. This is a preliminary assessment and has not yet been validated in the field. It is important to consider the characteristics of the source imagery used in the analyses when interpreting results. For damage assessments it should be noted that only significant damage to the structural integrity of the buildings analyzed can be seen in imagery, while minor damage such as cracks or holes may not be visible at all. For flood extractions using radar data it is important to note that urban areas and highly vegetated areas may mask the flood signature and result in underestimation of flood waters. Users with specific questions or concerns should contact unosat@unitar.org to seek clarification.

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Satellite detected water extent in N'Djamena department, N'Djamena Region, Chad as of 21 October 2022

**UNOSAT code FL20221019TCD** This map illustrates satellite-detected surface waters in N'Djamena Department, N'Djamena Region, Chad as observed from a Pleiades image acquired on 21 October 2022 at 10:35 local time. Within the analyzed area of about 500 km2, about 68 km2 of lands appear to be flooded and 13,323 structures are potentially affected by the floods. Based on Worldpop population data and the detected surface waters, about 228,000 people are potentially exposed or living close to flooded areas. This is a preliminary analysis and has not yet been validated in the field. Please send ground feedback to United Nations Satellite Centre (UNOSAT).