Glossary

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This page contains a list of technical and colloquial terms used in and around the OpenStreetMap project. It is mainly aimed at beginning mappers, or beginners in a particular area of the project: most definitions should be two lines at the most.

A · B · C · D · E · G ·  I  · J · K · L · M · N · O · P · Q · R · S · T · U · V · W · X


Note: The list is certainly not complete, and there are many more jargon words in and around OpenStreetMap. The page titles used in the wiki are often short and sweet, with a definition appearing at the top of most pages: you may find your answer by doing a search.

Please improve the Glossary by adding terms useful to beginning mappers (especially if you are one!). If there's any term you'd like to include and aren't sure of the definition, please add it with [STUB] where the definition would be.

A

  • API : Application Programming Interface (aka OSM Protocol). The API allows computer programs to access the OpenStreetMap database. It follows the REST approach to web service construction.
  • Applet : See Java Applet
  • Area : A shaded polygon representing, e.g., a park or a building. There is no data primitive for an area: they are represented as a closed ("circular") way having tags suited to areas.
  • Attribute : The properties of a real-world object, as represented by code in a database.

B

  • bar : See foo.

C

  • Carto : Properly, OSM Carto
  • Contributor : People who contribute edits and improvements to the Map and other OSM projects. (People like you!)

D

  • Database : Where OSM's underlying map data is kept. In simple terms this means information about what things are where in the world; technically a PostgreSQL installation running on various servers, but most applications access it via the API.
  • Data primitive : An obsolete term (in OSM) for Elements.
  • DWG : Data working group.

E

  • Editors: software and applications to edit features in the OpenStreetMap database. The human doing the editing is a Contributor.
  • Elements : The basic components of OpenStreetMap's conceptual data model of the physical world. They consist of "Nodes", "Ways" and "Relations".
  • Extent: The portion of area of a region show in a map. See Wikipedia:Map extent.

E

  • foo : Nonsense placeholder meaning "any value". Often used with bar, meaning "any other value".

G

  • GIS : Geographic information system (see also Wikipedia)
  • GNSS: Global Navigation Satellite System. Uses signals from satellites to establish where you are. There are several systems: GPS is probably the best known.
  • GNSS tracelog : A collection of records from a satnav system, known as "tracelog".
  • GPS : Global Positioning System. GNSS built and run by the government of the USA.
  • GPS receiver : Device used to establish your position. See GPS.
  • GPS trace: A time series of location points recorded by a GPS receiver, from which the route taken can be inferred (i.e. a GNSS tracelog).
  • GPS track : Variant of GPS trace
  • GPS unit : A GPS receiver
  • GPX : GPS Exchange Format: an XML format used to represent data collected by GPS units. The OSM server accepts data in GPX format before processing it into the OSM data model.

I

  • Imagery
  • Import : Uploading external data to OSM. Always consult!
  • iD : The main browser-based OSM editing software. (See also id.)
  • id or ID (also osm-id) : Usually refers to the unique reference numbers of Elements. For example, the id of this area is 263621287. Can also refer to the usernames or unique reference numbers of OpenStreetMap users: see User ID. See also iD.

J

  • Java may refer to these terms:
  • Java Applet : In an OpenStreetMap context you may hear mention of "the java applet" referring to a very old Editing interface which used to appear on the OpenStreetMap.org site superseded by Potlatch and then iD.
  • JOSM : The Java OpenStreetMap editor. It is a map viewing and editing tool written by Imi. It will run on most computers and allows a user to view, edit and upload data to the OpenStreetMap database.

K

  • key=value (also k=something v=something else; key/value pair) : Databases are arranged using "keys" (categories of information) and "values" (particular information). E.g., an object may have the data building=school: in this object "school" is the value specifying the category (key) of "building".Sometimes represented in the form k=building v=school, which is closer to the XML representation.

L

  • Layer : Is used to describe the relative height of map features, to separate different parts of style sheets, a way to show different things in JOSM, etc.
  • Licence : Usually the User Licence, the terms under which anyone can use OSM and its data. Sometimes refers to the Contributor Terms under which contributors licence their work to OSM and to the world in general.

M

  • 'The map' : Strictly, the database (unreadable by humans) of all OSM data. Also used in the conventional sense, i.e., a visual representation of real-world geography. (Check the context.)
  • Map Features
  • Mapping : This word is too ambiguous but many of us use it anyway:
  • Mapnik : Mapnik is a GIS library; a collection of code that does things like reprojecting and rendering geo-spatial data. Mapnik is used by OSM to generate tiles for the slippy map.
  • Mapping : The process of gathering data for the OSM map. Typically done by foot, bicycle or car with a GPS receiver and noting down street names in parallel.
  • Markup : A very simple computer language that allows an author to use special characters (e.g., ' / < >) to tell a computer how to display some text. There are at least three different markup systems in use across different OSM channels: it's optional, so don't let it put you off contributing!
  • Multipolygon
  • MWG : Membership Working Group

N

  • NMEA : Format used to represent data collected by GPS units.
  • Node : The simplest object in the database, consisting of a "point" with an ID, a latitude and a longitude. Nodes can also have tags. See Elements#Node

O

  • Object : Often used synonymously with OpenStreetMap "Elements" (Nodes, Ways & Relations. See above.), but can also refer to other technical concepts (ambiguous).
  • OCOSMD : Obsessive Compulsive OpenStreetMapping Disorder. Search for OCOSMD with your favourite search engine for examples.
  • OGC : The Open Geospatial Consortium (http://www.opengeospatial.org/). A non-profit body that defines standards for the use and storage of geospatial data.
  • Open : We try to do everything in the spirit of openness. Our maps are "open" in that anyone can use them (licensing issues notwithstanding), anyone can see how they were created, anyone can participate in that process. In addition most of our software is Open Source, meaning that software developers can participate in developing the project in that way.
  • Open Source : Software created in the spirit of openness, and with its source code open for downloading, modifying, and redistributing (for free). To avoid confusion, please don't refer to it as OS!
  • Operating System : Software such as Linux, Mac OS X, Windows or Solaris for low level management of a computer system. Hand-held devices also have one. To avoid confusion, please don't refer to it as OS!
  • Ordnance Survey : UK government mapping agency, with extremely detailed maps collected and funded by the taxpayer... and then sold back to them at prohibitively expensive prices. To avoid confusion, please don't refer to it as OS!
  • OS : May refer to any of three different things: "Open Source", "Operating System", and (in the UK) "Ordnance Survey".
  • OSGeo : The Open Source Geospatial Foundation. Promotes the development and use of Open Source, community-based Geospatial software.
  • OSM : OpenStreetMap. This whole project. See About.
  • OSMF : OpenStreetMap Foundation, a registered not-for-profit company which supports the OpenStreetMap project.
  • .osm : The XML format that is produced by the OSM server. It is used for communication with the API and also for the weekly Planet dumps.
  • OSM Carto : The 'standard' rendering of the map used on the website openstreetmap.org. NB not an 'official' rendering (there isn't one), but influential nevertheless.
  • Overpass : [STUB]
  • Overpass API : [STUB]
  • Overpass Turbo : [STUB]
  • Overpass Turbo Wizard : A tool that lets you build Overpass queries more easily than writing the query yourself.

P

  • Preset A user-customised list of tags that can be quickly added to an element during editing. (Mainly a JOSM term.)
  • Projection: A method of translating the roughly spherical surface of the earth to a flat display. The standard projection of OSM material is Plate Carree (no transformation, EPSG:4326). The standard projection for rendering OSM data onto map tiles is Spherical Mercator (EPSG:900913)
  • Protocol : The API.

Q

  • QL: A query language.
  • Query: If you want information from a human being, you ask them a question. If you want information from a database you send it a query.
  • Query language: Computers don't speak human, so your queries must be sent in a language the computer understands: in OSM this is usually Overpass QL.

R

  • Redaction: Removing from view data where the user did not agree to the new OpenStreetMap contributor terms and license change to Open Database License (ODBL). See [1]
  • regex or regular expression : Roughly, a pattern. These are used in a database query when you want to find any and all strings that match the pattern you specify.
  • Ref : a Tag used to enter reference numbers to objects, usually from official sources. For example, all parts of the motorway that runs from London to Cambridge get the tag "ref=M11" see Map_Features on the wiki.
  • Relation : A group of Elements that together behave as if they were a single Element. Each discrete Element is assigned a 'role' within the larger Relation.
  • REST : Web development paradigm which we adopt with our protocol interface (API). It means we make objects available at unique URLs, and follow standard use of HTTP protocol features.
  • Revert: may refer both for undoing deletions and partial or complete changeset rollbacks
  • Router : A service/device for working out a route between two geographical points using OSM or other map data (often for use as a navigation aid).
  • Rendering (noun) : The visual presentation of map features: one set of underlying data can be presented (rendered) in different ways.
  • Rendering (verb) : The process of turning raw geospatial data into a human-usable form.
  • Renderer : Any piece of software that renders the map database into usable form. Usually this means as image files analogous to a traditional paper map, but routers and other specialist software are also renderers.
  • Ruby : A multi-purpose programming language. We have a number of data manipulation scripts and libraries in Ruby. The protocol interface was originally written in pure Ruby before being ported to Ruby on Rails.
  • Ruby on Rails : Called "Rails" for short. A Ruby framework for rapid data-driven web development. OSM core components were ported to Ruby on Rails, see The Rails Port.
  • The Rails Port : OSM core components: The protocol interface (API) and the front end website components are often referred to as as "The Rails Port" because there was a large development effort to port these (change the code over) to Ruby on Rails. They were originally written in pure Ruby. The rails port runs on the Servers/www

S

  • Segment : Segments were a data primitive in old versions of the OSM API.
  • SiRFstar III : A GPS chipset by SiRF Technologies.
  • Slippy map : The word 'slippy' (rather than 'static') is used to highlight that a map image can be dragged around allowing a user to see what's off the edge of the display.
  • String : Any sequence of letters and numbers that a computer program treats as a unit. May have a natural language meaning, a computer language meaning, both, or neither.
  • Survey
  • SVG : Scaleable Vector Grapics. XML format for representing vector graphics. SVG maps can expoted using the export tab, or created by Osmarender.

T

  • Tagging : The act of adding tags to (key=value pairs) to elements, or the description of tags as in "Tagging scheme".
  • Tag : A representation of an attribute of some object in terms that a database can store. Each tag is a key=value pair. E.g., if a gate is open to all traffic, it can be tagged access=yes.
  • Talk page : A page for talking about a "main" page. E.g., this page is the Glossary. To talk about what's here, you can visit Talk:Glossary. Not to be confused with a User Talk page (see under "U").
  • Template : In the Wiki, a template is a piece of wiki markup that makes text display (render) in a special way (e.g., it may be in a different font). Using a template on a page is called "transcluding" a template: not only is it included, but it can later be changed centrally across (trans) all pages where it is found. See the MediaWiki manual: mw:Help:Templates
  • Tiles : Small image files that make up the slippy map. So called because of their arrangement in a grid.
  • Trace : A trace usually refers to a GPS trace (otherwise known a "GPS Track", see Recording GPS tracks) We use the word "trace" on the website: traces. Trace is also a verb, as in "Tracing" (Ambiguous. See following)
  • Tracing : Is ambiguous, either referring to sketching in data over aerial imagery (e.g. "tracing a building outline") or creating traces with a GPS receiver.
  • Track : The word track can either refer to a "GPS track" (see Recording GPS tracks), or to a type of footpath / rough road (see Track)
  • Tracklog : Yet another word for meaning the same as a GPS track / trace.

U

  • User ID : Strictly, an OSM user's unique identification number. May also refer to a user's User name. Every OSM user has one of each: the numerical user IDs are usually hidden, but are used in some downstream services as a more reliable identifier (they can't be changed).
  • User name (also "Display name") : The name you use to log in to OpenStreetMap. It also appears on your profile page, and in your profile page URL.
  • User talk page : A place where others can talk to you, in public, by posting messages to your personal page. The page address is User talk:<YourUsername>. Don't confuse it with a Talk page: see above under "T".

V

  • Value : The second part of a tag, which goes under a "key". See key=value.

W

  • Way : An ordered list of one or more Nodes. Ways get rendered as streets/railways/footpaths/canals etc according to the tag(s) set on them. Ways are continuous (they cannot have breaks) and non-branching.
  • wiki : (noun) A website that anyone can edit, not just somoone "official". See also here.
  • "Wiki, The" : This website, wiki.openstreetmap.org. The main reference point for information on everything in OSM. Mostly describes best/accepted practice but not always, and definitely not 'the last word'.
  • WGS84 : The ellipsoid that GPS is based upon. All geodata in OSM uses WGS84. This can be very different for geodata gathered from other sources. For example the Royal Observatory in Greenwich is at 0°0'0"E in the ellipsoid for OS maps, but at 0°0'5"W in WGS84.

See also

External resources