TheInstituto Geográfico Nacional (IGN), orNational Geographic Institute is a Spanishgovernment agency, dependent on the SpanishMinistry of Public Works. Founded in 1870, it is thenational mapping agency forSpain, together with theCentro Nacional de Información Geográfica (CNIG).
Since 2015, most of its products (includingMTN50 andMTN25topographic maps, andPNOAaerial photographies) are freely available online, and licensed under aCC-BY-4.0-like license, asFOM/2807/2015 decree requires its products must be released under afree license.[1][2]
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The IGN is responsible for:
MTN50, acronym forMapa Topográfico Nacional (National Topographic Map) scale 1:50,000, is produced by the National Geographic Institute (IGN), being obtained by direct processes of observation and measurement of the Earth's surface.[3] It constitutes, together with the MTN25, the official basic cartography of Spain.[4] It consists of a total of 1073 sheets.[5]
Its original publication began in 1875 and did not finish until 1968. In 1985, the updating of its sheets was stopped, to focus all efforts on the production of the then new National Topographic Map at a scale of 1:25,000 (MTN25).[6]
In 1999, the production of a new, completely renovated, MTN50 is resumed. This new MTN50 includes shading, and is generated by cartographic generalization processes, using digital technology, from the corresponding sheets of the MTN25. The publication of the first edition of this new digital MTN50 began in 1999, with sheet 605 (Aranjuez), and ended in 2010, with sheet 262 (Salvaterra de Miño), making a total of 1073 sheets.[5]
MTN25, acronym forMapa Topográfico Nacional (National Topographic Map) scale 1:25,000, consists, as of October 2017, of 4,098 sheets in vector format and 4,102 in raster format, sheets of 5' latitude by 10' longitude, a distribution that inherits the distribution table of the MTN50, with each one of the MTN50 sheets being divided into four quarters that are identified with Roman numerals (each one of the quarters making a MTN25 sheet), with slight modifications for sheets that cover very little territory.[7]
TheNational Plan for Aerial Orthophotography (in Spanish,Plan Nacional de Ortofotografía Aérea, abbreviated as PNOA) began in 2004 and aims to obtain digital aerialorthophotographs of the entire Spanish territory, with a fixed update period, currently 3 years.
The resolution of orthophotos has been changing over time and since 2017 the resolution is at least 25 cm, although in some areas resolutions of 15 cm are reached.
The PNOA is a cooperative project in which theGovernment of Spain and theAutonomous Communities participate. A single photogrammetric flight is carried out, and then a rigorous treatment of the data follows, in which technical specifications agreed upon by all the participating Public Administrations are complied. This approach of cooperative production between the different administrations is in accordance with the spirit of the Inspire Directive for the establishment of a Geographic Data Infrastructure in Europe, which seeks that the maximum level of detail of geographic information is captured only once and that it is shared openly among the different agents that need it.[8]
Media related toInstituto Geográfico Nacional (España) at Wikimedia Commons
