Description

Orthophotos are high-resolution, distortion-free, true-to-scale images of the Earth's surface. They are produced by photogrammetric methods in knowledge of the orientation parameters and with the addition of a digital terrain model from aerial images, which are available as vertical images. Over the years, orthophoto production has been constantly adapted to changing needs and technical progress. Orthophotos, for example, have various ground sampling distances (GSD). In the 1950s, the GSD was still 40 cm, i.e. one pixel in the image corresponds to 40 cm in reality. From 2014, orthophotos with a GSD of 10 cm were produced. The frequency and coverage of flights has also increased significantly over the years. Whereas before 1978 it was still commissioned work for special measures (road construction, land consolidation, urban development, etc.) that required aerial photography, a regular rotation of images was introduced from 1978 onwards. From 6-year cycles (1978-1993), to 5-year cycles (1994-2005), 3-year cycles (2006-2019) to 2-year cycles (to date). Orthophotos become historical as soon as they are replaced by DOP of current flight. Historical orthophotos from 1951 to 1969 can be found in the analogue DGK5 archive as raster or halftone slides. Through comprehensive scanning and quality assurance measures, all orthophotos were processed by Geobasis NRW in recent years until 1987. The orthophotos were produced in Gauss-Krüger tiles (EPSG:31466 and EPSG:31467) until 2009. In 2010, the company switched to UTM tiles (EPSG:25832). A download of the Gauss-Krüger tiles up to 2009 is possible via the factual data query of the metadata layer. Further information can be found on our website at: https://www.bezreg-koeln.nrw.de/geobasis-nrw/products-and-services/aerial-and-satellite imagery information/historical-aerial-and.

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Name	Format	Description	Link
	0		https://www.wms.nrw.de/geobasis/wms-t_nw_hist_dop?

WMS -T NW Historical Digital Orthophotos

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