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ORTHOPHOTO MOSAIC OF MAIO ISLAND — 17 NOVEMBER 1993

The aerial survey was carried out by KLM AEROCARTO using analogue photographic equipment.

The 1993 Maio island Orthophoto Mosaic was created from cartographic aerial photographs printed on photographic paper made available by the Maio Delegation of the Ministry of Agriculture and Environment. The island is not completely covered, with a small area at its south-western extremity missing. The material consists of seven flight lines. Alternate photographs were used, providing only complete 2D coverage.

The original aerial photographs on photographic paper were digitised at the Universidad de Las Palmas de Gran Canaria, Spain, in October 2019. The PDF files resulting from the digitisation were subsequently converted to TIFF format.

The images were georeferenced by Nuno de Santos Loureiro, University of Algarve, in 2026, as part of the GISCV.ORG project. A second-order polynomial transformation was applied, with a mean georeferencing error not exceeding 10 m for each photograph. A 2013 orthophoto mosaic provided by the INGT (Instituto Nacional de Gestão do Território, Cabo Verde) was used as the cartographic reference.

After georeferencing, the 48 available cartographic aerial photographs were subjected to grey-level normalisation using a common scale from 1 to 255, in order to ensure a homogeneous tonal representation across the dataset. Following completion of these procedures, the 48 georeferenced and normalised aerial photographs were combined into a single mosaic.

Three distinct core products were generated:

1) Cartogram, containing the footprint and centroid of each of the 48 cartographic aerial photographs (file: CV Maio 1993 footprint-centroids 32627.gpkg).
2) Single Orthophoto Mosaic, clipped to the boundary of Maio island and georeferenced in UTM Zone 27N (EPSG:32627) (file: CV Maio mosaico ortofotos 19931117 clip 32627.tif).
3) Complete set of the 48 cartographic aerial photographs, individually georeferenced in UTM Zone 27N (EPSG:32627) (file: CV Maio ortofotos 1993 clip 25m 32627 normalizados.zip).

Two additional products were also generated solely to provide a quick and convenient visual overview of the core products:

4) Figure showing the footprint or area covered by each aerial photograph, together with the corresponding geometric centroids and the administrative boundary of Maio Island (file: CV Maio CARTOGRAMA foto aérea cart 1993.jpeg).
5) Figure showing the orthophoto mosaic, together with the administrative boundary of Maio Island (file: CV Maio ORTOFOTOMOSAICO 1993.jpeg).

Products 1, 4 and 5 are available for free download and use under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence. Attribution to the original data source is required when using these products. Products 2 and 3 are subject to prior authorisation and can only be downloaded once such authorisation has been granted.

Example citations for GISCV.ORG are:  
 
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General Use Citation
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Please include the term 'GISCV.ORG' with a link to:
https://www.giscv.org
 
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Academic Use Citation
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If you use this GeoPackage in your work, please cite the source as follows:
GISCV.ORG. (YYYY, Month DD). Cartographic Aerial Photography. Produced by Nuno de Santos Loureiro. https://www.nsloureiro.pt/giscv/aerialphotography

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Thank you for citing your use of GISCV.ORG and for reporting any issues or errors you find.
As a non-profit academic project, your citations and messages are what keeps GISCV.ORG alive.
Nuno de Santos Loureiro (nlourei@ualg.pt)