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For other uses, see Geocoding (disambiguation).

Geocoding is the process of assigning geographic identifiers (e. g. , codes or geographic coordinates expressed as latitude-longitude) to map features and other data records, such as street addresses. A geographic coordinate system enables every location on the Earth to be specified in three coordinates using mainly a spherical coordinate system. Latitude, usually denoted symbolically by the Greek letter phi ( Φ) gives the location of a place on Earth (or other planetary body north or south of the Longitude (ˈlɒndʒɪˌtjuːd or ˈlɒŋgɪˌtjuːd symbolized by the Greek character Lambda (λ is the east-west Geographic coordinate measurement House numbering is the system of giving a unique Number to each Building in a Street or Area, with the intention of making it easier to locate You can also geocode media, for example where a picture was taken, IP addresses, and anything that has a geographic component. An Internet Protocol ( IP) address is a numerical identification ( Logical address) that is assigned to devices participating in a Computer network With geographic coordinates the features can be mapped and entered into Geographic Information Systems.

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

Contents

Address interpolation

A simple method of geocoding is address interpolation. In the mathematical subfield of Numerical analysis, interpolation is a method of constructing new data points within the range of a Discrete set of This method makes use of data from a street geographic information system where the street network is already mapped within the geographic coordinate space. Each street segment is attributed with address ranges (e. g. house numbers from one segment to the next). Geocoding takes an address, matches it to a street and specific segment (such as a block, in towns that use the "block" convention). A city block, urban block or simply block is a central element of Urban planning and Urban design. Geocoding then interpolates the position of the address, within the range along the segment.

Example

Take for example: 742 Evergreen Terrace

Let's say that this segment (for instance, a block) of Evergreen Terrace runs from 700 to 799. 742 Evergreen Terrace is the Fictional Street address of the home for the fictional Simpson family in the animated Even-numbered addresses would fall on one side (e. g. west side) of Evergreen Terrace, with odd-numbered addresses on the other side (e. g. east side). 742 Evergreen Terrace would (probably) be located slightly less than halfway up the block, on the west side of the street. A point would be mapped at that location along the street, perhaps offset some distance to the west of the street centerline.

Complicating factors

However, this process is not always as straightforward as in this example.

Difficulties arise when:

While there might be 742 Evergreen Terrace in Springfield, there might also be a 742 Evergreen Terrace in Shelbyville. Asking for the city name (and state, province, country, etc. as needed) can solve this problem. Some situations require use of postal codes or district name for disambiguation. A postal code (known in various countries as a post code, postcode, or ZIP code) is a series of letters and/or digits appended to a For example, there are multiple 100 Washington Streets in Boston, Massachusetts[1] because several cities have been annexed without changing street names. The Commonwealth of Massachusetts ( is a state located in the New England region of the northeastern United States.

Finally, several caveats on using interpolation.

A very common error is to believe the accuracy ratings of a given map's geocodable attributes. Taking one specific vendor as an example, who claims a "99% match" in selected areas - the "match" simply means that the address was found in the attributes. It does not mean the address is attributed to the correct segment, or that the attribution of that segment will interpolate a correct result when this specific address is tried. In truth, the actual "wrong" count will be higher; if an address geocodes to a location that is off by 160 miles in the middle of the ocean (true case), it will still typically be counted as "correct" by the map vendor, since the address was found in the attributes. Such "accuracy" currently touted by most vendors has no bearing on an address being attributed to the correct segment, being attributed to the correct "side" of the segment, nor resulting in an accurate position along that correct segment. With the geocoding process used for U.S. Census TIGER datasets, 5-7. The United States Census is a decennial Census mandated by the United States Constitution. 5% of the addresses may be allocated to a different census tract, while 50% of the geocoded points might be located to a different property parcel. A census tract, census area, or census district is a particular Community defined for the purpose of taking a Census. [2]

Because of this, it is quite important to avoid using interpolated results except for non-critical applications, such as pizza delivery. Pizza delivery is a service in which a pizzeria delivers a Pizza, usually ordered by telephone or Internet to a customer Interpolated geocoding is usually not appropriate for making authoritative decisions, for example if life safety will be impacted by that decision. Emergency services, for example, do not make an authoritative decision based on their interpolations; an ambulance or fire truck will always be dispatched regardless of what the map says.

Other techniques

Other means of geocoding might include locating a point at the centroid (center) of a land parcel, if parcel (property) data is available in the geographic information system database. In rural areas or other places lacking high quality street network data and addressing, GPS is useful for mapping a location. Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth For traffic accidents, geocoding to a street intersection or midpoint along a street centerline is a suitable technique. Most highways in developed countries have mile markers to aid in emergency response, maintenance, and navigation. It is also possible to use a combination of these geocoding techniques - using a particular technique for certain cases and situations and other techniques for other cases.

Privacy concerns

The proliferation and ease of access to geocoding (and reverse-geocoding) services raises privacy concerns. For example, in mapping crime incidents, law enforcement agencies aim to balance the privacy rights of victims and offenders, with the public's right to know. Law enforcement agencies have experimented with alternative geocoding techniques that allow them to mask some of the locational detail (e. g. , address specifics that would lead to identifying a victim or offender). As well, in providing online crime mapping to the public, they also place disclaimers regarding the locational accuracy of points on the map, acknowledging these location masking techniques, and impose terms of use for the information. Crime mapping is used by analysts in law enforcement agencies to map visualize and analyze crime incident patterns

See also

References

  1. ^ Google Maps
  2. ^ Ratcliffe, Jerry H. Geotagging is the process of adding geographical identification Metadata to various media such as photographs video websites or RSS feeds and is a form of Geolocation refers to identifying the real-world geographic location of an Internet connected computer mobile device website visitor or other A geocoded photograph is a Photograph which is associated with a geographical location C-squares (acronym for the concise spatial query and representation system) is a system of Geocodes (actually a type of global grid) that provides QDGC - Quarter Degree Grid Cells (or QDS - Quarter degree Squares are a way of dividing the Longitude Latitude degree square cells into smaller squares forming in (2001). "On the accuracy of TIGER-type geocoded address data in relation to cadastral and census areal units". International Journal of Geographic Information Sciences 15 (5).  

External links

Dictionary

geocoding

-verb

  1. Present participle of geocode.
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