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Georeferencing Introduction to georeferencing

ESTP course on Geographic Information Systems (GIS): Use of GIS for making statistics in a production environmentStatistics Norway, Oslo, 26th to 30th of March 2012

Attribution (by) Licensees may copy, distribute, display and perform the work and make derivative works based on it only if they give the author or licensor the credits in the manner specified by these. http://creativecommons.org/licenses/by/3.0/

Mr Vilni Verner Holst BlochMSc Resourcs Geography and Landscape EcologyStatistics Norway460 Construction and service statisticsOterveien 23 N-2225 Kongsvinger NORWAYvvh@ssb.noTel: +47 6288 5097Mob. +47 9482 2532

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Content

• Georeferencing

• Geocoding

• Reverse geocoding

• Geocoder

• Excercise

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Georeferencing

• To georeference something means to define its existence in physical space. That is, establishing its location in terms of map projections or coordinate systems.

• The term is used both when establishing the relation between raster or vector images and coordinates, and when determining the spatial location of other geographical features.

• Examples would include establishing the correct position of an aerial photograph within a map or finding the geographical coordinates of a place name or street address.

• Most georeferencing tasks are undertaken either because the user wants to produce a new map or because they want to link two or more different datasets together by virtue of the fact that they relate to the same geographic locations.

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Georeferencing needs

• Georeferencing is crucial to making aerial and satellite imagery, usually raster images, useful for mapping as it explains how other data, such as the above GPS points, relate to the imagery.

• Very essential information may be contained in data or images that were produced at a different point of time. It may be desired either to combine or compare this data with that currently available. The latter can be used to analyze the changes in the features under study over a period of time.

• Different maps may use different projection systems. Georeferencing tools contain methods to combine and overlay these maps with minimum distortion.

• It may be required to establish the relationship between social survey results which have been coded with postal codes or street addresses and other geographic areas such as census zones or other areas used in public administration or service planning.

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Georeferencing hardware

Artist's conception of GPS Block II-F satellite in Earth orbit.

Civilian GPS receiver in a marine application.

Automotive navigation system in a taxicab.

GPS receivers are now integrated in many mobile phones.

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Georeferencing methods

• There are various GIS tools available that can transform image data to some geographic control framework, like ArcMap, PCI Geomatica, or ERDAS Imagine. One can georeference a set of points, lines, polygons, images, or 3D structures. For instance, a GPS device will record latitude and longitude coordinates for a given point of interest, effectively georeferencing this point. A georeference must be a unique identifier. In other words, there must be only one location for which a georeference acts as the reference.

• In situations where data has been collected and assigned to postal or area codes, it is usually necessary to convert these to geographic coordinates by use of a definitive directory or gazetteer file. Such gazetteers are often produced by census agencies, national mapping organizations or postal service providers. At their simplest, these may simply comprise a list of area codes or place names and another list of corresponding codes, names or coordinate locations. The range and purpose of the codes available is country-specific. An example is the UK's National Statistics Postcode Directory which shows each postcode's membership of census, administrative, electoral and other geographical areas. In this case, the directory also provides dates of creation and deletion, address counts and an Ordnance Survey grid reference for each postcode, allowing it to be mapped directly. Such gazetteer files support many web-based mapping systems which will place a symbol on a map or undertaken analysis such as route-finding, on the basis of postal codes, addresses or place names input by the user.

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List of some geocoding systems(some of these code systems are free for use, others have different licences):

• ISO 6709 Standard Representation for Geographic Point Location by Coordinates• C-squares - compact encoding of geographic coordinate bounds (latitude-longitude)• FIPS country codes (FIPS 10-4), area code, administrative, free• IATA airport codes, area /point codes, airports• ICAO airport codes, area /point codes, airports• IANA country codes similar to ISO 3166-1 alpha-2• IOC country codes, area, worldwide• ISO 3166 country and subdivision codes• NUTS area code, partially administrative, worldwide: countries, Europe : country to community• ONS code, UK only, administrative• OpenPostcode algorithm applied for geocoding Irish locations.• Postal codes, area, worldwide, country-codes by UPU, free• Quarter Degree Grid Cells• UN M.49 region codes, area code, continents, countries (like ISO 3166-1 numeric)• SALB (Second Administrative Level Boundaries), by UN [2]• UN/LOCODE, area, administrative, cities• WMO squares

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Geocoding

• Geocoding is the process of finding associated geographic coordinates (often expressed as latitude and longitude) from other geographic data, such as street addresses, or zip codes (postal codes). With geographic coordinates the features can be mapped and entered into Geographic Information Systems, or the coordinates can be embedded into media such as digital photographs via geotagging.

• Reverse geocoding is the opposite: finding an associated textual location such as a street address, from geographic coordinates.

• A geocoder is a piece of software or a (web) service that helps in this process.

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Reverse geocoding

• Reverse geocoding is the opposite geocoding: finding an associated textual location such as a street address, from geographic coordinates.

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Geocoder

• A geocoder is a piece of software or a (web) service that helps in this process.

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Hands-on exercise:

Georeferencing

ESTP course on Geographic Information Systems (GIS): Use of GIS for making statistics in a production environmentStatistics Norway, Oslo, 26th to 30th of March 2012

Attribution (by) Licensees may copy, distribute, display and perform the work and make derivative works based on it only if they give the author or licensor the credits in the manner specified by these. http://creativecommons.org/licenses/by/3.0/

Mr Vilni Verner Holst BlochMSc Resourcs Geography and Landscape EcologyStatistics Norway460 Construction and service statisticsOterveien 23 N-2225 Kongsvinger NORWAYvvh@ssb.noTel: +47 6288 5097Mob. +47 9482 2532

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Vision: Georeference all NICUs in EuropeExample: Newborn Intensive Care Units in Belgium

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Geocoding task• Find a post address list for all/part of the hospitals in your

country (e.g. using internet phonebook, wikipedia or national health portal)

• Prepare hospital list in Excel (arrange columns, column titles, divide into; hospital-id, country, region, street address etc)

• Use www.batchgeo.com to geocode• Display and and download as kml-file• Inspect kml-file structure in a simple text-editor• Download shape-files for your country (or part of) from

Geofabrik: http://www.geofabrik.de/data/download.html From point.shp find ”hospital”

• Compare and describe ”your” hospitals with the Geofabrik/OSM hospitals