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This page contains a list of technical and colloquial terms used in and around the OpenStreetMap project.
Note: It's fairly arbitrary what has been included on this page. This list is certainly not complete. There are very many jargon words, and names of software in and around OpenStreetMap. In fact the page titles used throughout the wiki will often be short and sweet, often single words, with a definition appearing at the top of the page, and so you may find better coverage of a term by doing a search.
- API : Application Programming Interface - The OSM API provides high-level access to the OpenStreetMap database by allowing clients to request and edit objects from the database. It follows the REST approach to web service construction. A.K.A The OSM "Protocol"
- Applet : See Java Applet
- Area : In map rendering terms, an area is a shaded polygon representing for example a park or industrial area. There is no data primitive for an area. They are just represented as a way that closes in on itself (i.e. circular) and is tagged with tags that belong on areas.
- Database : The OSM "database" is where we keep our underlying map data (in simple terms this means information about what is where). Technically speaking it's actually a PostgreSQL installation running on various servers, but most applications access it via the API
- Data Primitive : old term for low level data types: nodes, ways and relations. We've mostly phased out this terminology in favour of Elements.
- Elements : The basic components of OpenStreetMap's conceptual data model of the physical world. They consist of "Nodes", "Ways" and "Relations".
- GIS : Geographic information system (see also Wikipedia)
- GNSS: Satnav system, world isn't limited to GPS system
- GNSS tracelog - collection of records from a satnav system, known as "tracelog"
- GPS Receiver : Global Positioning System Receiver. Device used to record your position using satellite signals.
- GPS trace: term for data collected by GPS units (i.e. "GNSS tracelog").
- GPS track : variant of GPS trace
- GPS Unit : Another name for a GPS Receiver
- GPX : GPS Exchange Format is 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.
- iD - ID stands for identifier, but iD is also the name of our main browser-based editing software... which might be confusing. We do use identifiers and talk about ids a lot in an OpenStreetMap technical context. Often we are referring to numerical identifiers of the Elements, or of OpenStreetMap users (see User ID)
- 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="something" v="something else" see tags
- Key : The First Part of a tag representing a broader grouping or category. The second part of tag is the Value (key-value pairs)
- 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.
- Map Features
- Mapping - this word is too ambiguous but many of us use it anyway:
- "Mapping" to describe process of using Editors
- "Mapping" to describe process of surveying/collecting data
- "Mapping techniques" to describe Category:Data collection technique
- "Mapping party" to process of surveying/collecting data
- "Mapping party" to describe recent Category:Events
- "Armchair mapping" to describe process of Tracing Aerial Imagery without actually surveying it on the ground (yes! we overuse "mapping" at every step)
- 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.
- NMEA : format used to represent data collected by GPS units
- Node : An object with an ID, a Latitude and a Longitude. Nodes can also have tags. See Data Primitives#Node and XML Schema#Node
- Object : Often used to refer to OpenStreetMap "Elements" (Nodes, Ways & Relations. See above) but can 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/) is a non-profit standards 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. Devices also have them. To avoid confusion, please don't refer to it as OS!
- Ordnance Survey - Mapping organisation in the UK, 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 : Unfortunately OS is an abbreviation for three different things which we might be talking about in this context: see "Ordnance Survey", "Open Source", or "Operating System" above.
- 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
- .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.
- Osmarender : The renderer used by the Tiles@home project, also the name of the tiles@home default layer because of this.
- Planet.osm : An osm format file that contains all of the nodes, relations and ways that are stored in the OSM database.
- Plugin (JOSM term):
- PostGIS : http://postgis.refractions.net/ An extension to the PostgreSQL database that allows it to store OGC Simple Feature Specifications compliant objects. PostGIS is used by OSM along with Mapnik to generate tiles for the Slippy Map.
- Potlatch : That supersedes the Java Applet for the editing the map online through the web site.
- Preset (mainly JOSM term)
- Projection: The standard "projection" of OSM material is Plate Carree (no transformation, EPSG:4326), the standard projection for rendered OSM data, i.e. map tiles, usually is Spherical Mercator (EPSG:900913)
- Protocol : A.K.A. The "API".
- 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 
- Ref : a Tag used to enter reference numbers to i.e. roads. For example the M 24 gets the key/value "ref=M 24" see Map_Features on the wiki.
- Relations : Relations are a new kind of data primitive added more recently. They are basically groups of objects in which each object may take on a specific role. Relations may also have tags.
- 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).
- 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
- Segment : Segments were a data primitive in the past (in old OSM API versions).
- 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.
- SVG : Scaleable Vector Grapics. XML format for representing vector graphics. SVG maps can expoted using the export tab, or created by Osmarender.
- Tagging : The act of adding tags to (key=value pairs) to elements, or the description of tags as in "Tagging scheme".
- Tag : A tag is a key=value pair, set on OpenStreetMap entities like Node, Way or Relation. Each tag consists of a key name and a value. This is written as key=value (e.g. highway=residential) or sometimes as k=key, v=value (k=highway v=residential) which is closer to how the XML representation looks.
- 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.
- User ID : With OpenStreetMap users have names and also numerical ID numbers. "User ID" might refer to either of these. More correctly used for the latter. The numerical user IDs are largely hidden, but available in planet dumps, and used in some downstream services as a more reliable (can't be changed!) identifier
- User Name : Or "Display name" is the name you use to login with on the OpenStreetMap site. It also appears on the profile page, and in the profile page URL.
- Value : The Second Part of a tag, which goes under a Key.
- Way : An ordered list of one or more Nodes. Ways get rendered as streets/railways/footpaths/canals etc according to the tag(s) indicating what type of way it is. Ways are contiguous and non-branching. (You can get from beginning to end by following segments of the way, without "jumping" or backtracing) See Data Primitives#Way and XML Schema#Way
- 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.
- Category:Disambiguation - this category may not help you if you are just reader