Aerial photography [BD ORTHO® Historique - IGN-F] - Department of Calvados - 1955

BD ORTHO® History of 1955 produced by IGN throughout the Department of Calvados. The product BD ORTHO® Historique 1955 is a collection of digital mosaics of ancient panchromatic orthophotographs (grey levels) rectified in the projection adapted to the departmental territory (Calvados). BD ORTHO® Historical 1955 is freely distributed under an open license thanks to the financial support of the Department of Calvados. The ORTHO® Historical comic consists of digital images (without cladding or overloading) and georeferencing indications. The information content allows local use up to 1: 2,000 to develop the territory. The ORTHO® Historical BD 1955 offers many advantages: - Spatial planning: land use, land consumption and new communication routes; - environment: coastal and forest observatory, bocage management; - Communication: visualization of the evolution of the territory. The original files distributed by the Department of Calvados under Open License are: - legal projection Lambert 93 NTF (Paris) / Lambert zone I (EPSG: 2154); - in ECW format per 10km x 10km slab; - with a resolution of one pixel = 50 cm; - compressed as a zip archive. You will find below the links to access the "multi-part" files for free download. To unzip the "multi-part" files: - Make sure you have downloaded all parts: 001, 002, 003... - Put all the parts in the same directory - Click on file 001 (ex: ecw_1947.zip.001). No need to click on 002, 003, 004... Opening the .001 file opens all other parts of the archive. In order to facilitate the use of these orthophotos, the files proposed here are in GeoPackage OGC format in lambert 93. **Collection context** The number of shots needed to cover a department is important, these shots have strong disparities in sunshine, colored appearance, landscape, behavior of objects (quarries, sands, water surfaces, ...) and sometimes season. In practice the process seeks to correct each image of the internal effects of illumination and color related to sunlight. All images must also be homogenized. For each image we apply a correction of illumination (hot-spot and vignetting). Once this correction is applied, the images are globally equalized on the entire site. We can add that on some shots, the use of short focal lengths or these wide-field cameras has generated vignetting effects (difference of illumination between the center and the edge of the image) important and more difficult to correct. **Collection method** The Geopakage was produced from the GDAL library: * gdalbuildvrt D:\2_Ortho_1955\1955.vrt -addalpha -srcnodata 255 -hidenodata D:\2_Ortho_1955\data\*.ecw * gdalwarp D:\2_Ortho_1955\1955.vrt D:\2_Ortho_1955\1955.gpkg -t_srs EPSG:2154 -r cubic -of GPKG * gdaladdo -r cubic D:\2_Ortho_1955\1955.gpkg 4 16 64 256 For more information, see [Isogeo Catalog Metadata](https://open.isogeo.com/s/434296189d794266a04a8678e256f0c4/HiLeps3y1qrSx6aTDmKyp0spGPix0/r/aa8e61cbb1de436c89b905a787429046).