Orthoimagery

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Orthoimagery


Orthoimagery is geo-referenced rectified image data of the Earth's surface, from satellite or airborne sensors. Although technically not a theme in its own right, orthoimagery is included as, when interpreted, it’s a widely-used data source for many other data themes.

Why is this theme fundamental?

Orthoimagery is used to produce, update or complement topographic data (by providing greater detail). It’s very often the main source for Land Cover data. It can be produced relatively quickly from satellite images and is therefore suitable to assess temporary phenomena, such as damages after a disaster or the impact of pollution.

It’s useful for either human visualisation or machine interpretation. This image data is a record of the Earth’s surface at the time of imaging, which then has immense historical value in the future.

Orthoimagery may be exploited using algorithms for automatic processing to extract features and information such as buildings, roads, vegetation, soil moisture & water content, cloud cover, and to detect changes such as land use.

Which sustainable development goals (SDGs) will it help to meet?

Orthoimagery is a potential data source for SDGs 2,6,9,11,14,15.

Geospatial data features in more detail

The Orthoimagery theme includes image products generated from sensors aboard drones, aircraft or satellites. Sensors may produce multispectral data, giving images either in true colours, black and white, or scenes based on infrared or radar sensors. Once captured by the sensor, these images may be subject to a variety of treatments which are designed to increase data interpretation capabilities.

Possible sources of data

Many organisations produce and distribute orthoimagery for several purposes. National Mapping Agencies usually carry out periodical space/aerial photo capture and orthophoto production through national programmes. Some private companies do the same for commercial reasons, covering large parts of the Earth. Public and private remote sensing satellite operators capture massive amounts of satellite images which are distributed through multiple channels, both commercial and non-commercial.

Existing Data Standards

Note: This is indicative. Other lists of standards exist and UN-GGIM will seek to work with thematic experts to develop a list of relevant data standards.

INSPIRE Data Specification on Orthoimagery – Technical Guidelines;
FGDC content standards for digital orthoimagery; and,
USGS National Geospatial Program. Digital Orthoimagery Base Specification V1.0.