Find geospatial, GIS, LBS terminology definitions.

AJAX

The page-reload cycle presents one of the biggest usability obstacles in Web application development and is a serious challenge for Java™ developers. Ajax (Asynchronous JavaScript and XML) is a programming technique that lets you combine Java technologies, XML, and JavaScript for Java-based Web applications that break the page-reload paradigm.

Ajax, or Asynchronous JavaScript and XML, is an approach to Web application development that uses client-side scripting to exchange data with the Web server. As a result, Web pages are dynamically updated without a full page refresh interrupting the interaction flow. With Ajax, you can create richer, more dynamic Web application user interfaces that approach the immediacy and usability of native desktop applications.

Ajax isn't a technology, it's more of a pattern -- a way to identify and describe a useful design technique. The current buzz is because of the emergence in 2004 and 2005 of some great dynamic Web UIs based on Ajax technology, most notably Google's GMail and Maps applications and the photo-sharing site Flickr. These UIs were sufficiently groundbreaking to be dubbed "Web 2.0" by some developers, with the resulting interest in Ajax applications skyrocketing.

The iPointer Toolbox makes extensive use of AJAX.

For more-detailed information on the programmatic workings of Ajax, see A Hype-Free Introduction to Ajax.

Source: Ajax for Java Developers: Build dynamic Java applications by Philip McCarthy.

 
Bluetooth

In general, a wireless connection that enables devices such as mobile phones and assessories to communicate with each other.

More specific, Bluetooth is a technical industry standard that facilitates communication between wireless devices. Wireless communication is possible over a short distance, typically about 30ft/10m.

For more information see www.bluetooth.org and www.bluetooth.com .

 
BTGPS

A GPS receiver with a bluetooth wireless connection.

 
Compass

A compass (or mariner's compass) is a navigational instrument for finding directions on the earth. It consists of a magnetised pointer free to align itself accurately with Earth's magnetic field, which is of great assistance in navigation. The cardinal points are north, south, east and west (a formal model for determining cardinal directions based on topological relations was developed at the National Center for Geographic Information and Analysis). Because a compass points to the Earth's magnetic field, Magnetic Declination  (see below) has to be considered.

Small compasses found in clocks and other electronic gear are Solid-state electronics usually built out of two or three magnetic field sensors that provide data for a microprocessor. Using Trigonometry the correct heading relative to the compass is calculated.

Often, the device is a discrete component which outputs either a digital or analog signal proportional to its orientation. This signal is interpreted by a controller or microprocessor and used either internally, or sent to a display unit. The sensor uses precision magnetics and highly calibrated internal electronics to measure the response of the device to the Earth's magnetic field. The electrical signal is then processed or digitized.

The following is a description of such compasses from Honeywell:

Two-axis magnetic compasses measure the horizontal vector components of the earth's magnetic field using two sensor elements in the horizontal plane but orthogonal to each other. Called the X and Y-axis sensors, each sensor on an electronic compass assembly measures the magnetic field in its sensitive axis and the arc tangent Y/X provides the heading of the compass with respect to the X-axis. A two-axis compass can remain accurate as long as the sensors remain horizontal, or orthogonal to the gravitational (downward) vector. In moving platform applications, two axis compasses are mechanically "gimbaled" to remain flat and accurate.

Three-axis magnetic compasses contain magnetic sensors in all three orthogonal vectors of an electronic compass assembly to capture the horizontal and vertical components of the earth's magnetic field. To electronically gimbal the compass, the three magnetic sensors are complemented by a tilt-sensing element to measure the gravitational direction. The tilt sensor provides two-axis measurement of compass assembly tilt, known as pitch and roll axis. The five axes' of sensor inputs are combined to create a "tilt-compensated" version of the X and Y-axis magnetic vectors, and then computed into a tilt-compensated heading. For further interest, please see the technical papers and application notes.

Reference: Honeywell Electronic Compassing Solutions

This article is licensed under the GNU Free Documentation License. It uses material from the Compass article.

 
EGNOS

The European Geostationary Navigation Overlay Service (EGNOS) augments the two military satellite navigation systems now operating, the US NAVSTAR GPS and Russian GLONASS. EGNOS reports on the relilabilty and accuracy of the positioning signals of the two systems. Three geostationary satellite transmit this information which is obtained by a network of ground stations. It will allow users in Europe and beyond to determine their position to within 5m compared to 20m.

EGNOS is a joint project of the Europen Space Agency and the Europen Commicion and EuroControl, the European Organisation for the Safety of Air Navigation.

WAAS is a similar technology, serving the territory of the USA and beyond.

 
EPSG and OPG

The European Petroleum Survey Group (EPSG) was a scientific organization with ties to the European petroleum industry. It specialized in applied geodesy, surveying and cartography related to oil exploration. EPSG also compiled an extensive database of Earth ellipsoids, datums, and geographic and projected coordinate systems, the EPSG Geodetic Parameter Dataset.

In 2005, the newly formed OGP Surveying and Positioning Committee replaced EPSG.

The iPointer Platform stores its geographic data using Oracle Locator, which in turn, follows the definitions of the  EPSG Geodetic Parameter Dataset.

 
Galileo

The Galileo positioning system is a staellite navigation system currently built by the European Union (EU) as an alternative to American NAVSTAR and the Russian GLONASS. The system is expected to be operational by 2008/2009.

Galileo will be compatible with NAVSTAR, substantially increasing the number of available satellites. 

In January 2006, the European Space Agency successfully launched the first Galileo Satellite into orbit. When completed, the GALILEO system will consist of 30 satellites. Improvements to GPS technology will make GALILEO more accurate than current implementations. The position accuracy is expected to be 1 meter.

Geocoding 

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 and even media. With geographic coordinates, the features can then be mapped and entered into Geographic Information Systems.

Address interpolation is a simple method of geocoding. This method makes use of street GIS data, 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. Geocoding then interpolates the position of the address, within the range along the segment.

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 GIS database. In rural areas or other places lacking high quality street network data and addressing, GPS is useful for mapping a location. 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.

This article uses material from the Geocoding article.

Geofencing 

Restricting the movement of a vehicle or other object to within a specified area. The location of the vehicle is monitored by telemetry and an alarm raised if it goes outside that area.

Geotagging

Geotagging is the process of adding geographical identification metadata to various media such as websites, RSS feeds, or images. This data usually consists of latitude and longitude coordinates, though it can also include altitude and place names.

Geotagging can help users find a wide variety of location-specific information. For instance, one can find images taken near a given location by entering a latitude and longtitude into a Geotagging-enabled image search engine. Geotagging-enabled information services can also potentially be used to find news, websites, or other resources.

This article uses material from the Geotagging article.

GIS

A Geographic Information System (GIS) is a system for creating, storing, analyzing and managing spatial data and associated attributes. In the strictest sense, it is a computer system capable of integrating, storing, editing, analyzing, sharing, and displaying geographically-referenced information. In a more generic sense, GIS is a tool that allows users to create interactive queries (user created searches), analyze the spatial information, and edit data. Geographic Information Science is the science underlying the applications and systems, taught as a degree programme by several universities.

Geographic information systems technology can be used for scientific investigations, resource management, asset management, Environmental Impact Assessment, development planning, cartography, and route planning.

This document contains data found in the Wikipedia's GIS article.

GLONASS

The Global Navigation Satellite System (GLONASS) is Russian's counterpart to the US GPS and the currently developed European GALILEO. It is developed and maintained by the Russian Space Agency. Like GPS, the system consists of 24 satellites, transmitting positioning signals to GLONASS receivers.

 
GPS

The Global Positioning System (GPS) is a worldwide radio-navigation system formed from a constellation of 24 satellites and their ground stations. The United States Department of Defense developed the system, officially named NAVSTAR GPS (Navigation Signal Timing and Ranging GPS), and launched the first experimental satellite in 1978. GPS is available for free use in civilian applications as a public good. GPS satellites broadcast precise timing signals to GPS receivers, allowing them to accurately determine their location, longitude (see below), latitude (see below), and altitude, anywhere on Earth. GPS has become a vital global utility, indispensable for modern navigation on land, sea, and air around the world, as well as an important tool for map-making and land surveying. These days GPS has found its way into cars, boats, planes, construction equipment, movie making gear, farm machinery, even laptop computers, and mobile phones. In the USA, the FCC has mandated that all mobile phone calls can be located to 50/150 meters 66%/95% of the time. This mandate is referred to as Enhanced 911 (E911) and has led many mobile phone companies to include GPS receiver in their mobile phones.

Navigation signals

GPS satellites broadcast three different types of data in the primary navigation signals. The first is the almanac which sends coarse time information with second precision along with status information about the satellites. The second is the ephemeris, which contains orbital information that allows the receiver to calculate the position of the satellite at any point in time. These bits of data are folded into the 37,500 bit Navigation Message, or NM.

The satellites also broadcast two forms of accurate clock information, the Coarse Acquisition code, or C/A, and the Precise code, or P-code. The former is normally used for most civilian navigation. Each satellite sends a distinct C/A code, which allows them to be identified.

Calculating positions

The basis of GPS positioning is "trilateration" from satellites. Trilateration is a method of determining the position of objects in a similar fashion as triangulation. Unlike triangulation, which uses angle measurements to calculate an objects location, trilateration uses known location of two or more reference points, and the measured distance between the object and each reference point. In the case of GPS positioning, the reference points are the satellites and the measured distance is measured between each satellite and the GPS receiver. Satellites communicate their position to the GPS receiver, not the other way around.

This document contains data found in the Wikipedia's GPS article.

 
Latitude

Latitude, usually denoted symbolically by the Greek letter φ (phi), gives the location of a place on Earth north or south of the Equator. Latitude is an angular measurement in degrees (marked with °) ranging from 0° at the Equator to 90° at the poles (90° N for the North Pole or 90° S for the South Pole).

A specific latitude may then be combined with a specific longitude (see below) to give a precise position on the Earth's surface.

All locations of a given latitude are collectively referred to as a circle of latitude or line of latitude or parallel, because they are coplanar, and all such planes are parallel to the Equator. Lines of latitude other than the Equator are approximately small circles on the surface of the Earth; they are not geodesics since the shortest route between two points at the same latitude involves moving farther away from, then towards, the equator.

Four lines of latitude are named because of the role they play in the geometrical relationship with the Earth and the Sun:

    •    Arctic Circle — 66° 33′ 39″ N

    •    Tropic of Cancer — 23° 26′ 22″ N

    •    Tropic of Capricorn — 23° 26′ 22″ S

    •    Antarctic Circle — 66° 33′ 39″ S

Only at latitudes between the Tropics is it possible for the sun to be at the zenith. Only north of the Arctic Circle or south of the Antarctic Circle is the midnight sun possible.

The reason that these lines have the values that they do lies in the axial tilt of the Earth with respect to the sun, which is 23° 26′ 22″.

Note that the Artic Circle & Tropic of Cancer and the Antarctic Cirlce and Tropic of Capricorn are co-latitudes since the sum of their angles is 90.

This article is licensed under the GNU Free Documentation License. It uses material from the Latitude article.

Location-based Services 

A location-based service (or LBS) in a cellular telephone network is a service provided to the subscriber based on her current geographic location. The cell-phone service provider gets the location from a GPS chip built into the phone, or using radiolocation and trilateration based on the signal-strength of the closest cell-phone towers (for phones without GPS features).

One example of a location-based service might be to allow the subscriber to find the nearest business of a certain type, such as an Italian restaurant. The ability of the restaurant to send an invitation to bypassers has also been mentioned, even though this might be regarded as unsolicited commercial email or spamming.

With the passing of the Can Spam Act in 2005, it became illegal in the United States to send any message to the end user without the end user specifically opting-in. This put an additional challenge on LBS applications as far as 'carrier-centric' services were concerned. As a result, there has been a focus on user-centric location-based services and applications which give the user control of the experience, typically by opting in first via a website (for example dodgeball) or by text messaging screens in locations (for example at rock concerts).

In the U.S. the FCC requires that all carriers meet certain criteria for supporting location-based services (FCC 94-102). The mandate requires 95% of handsets resolve within 300 meters for network-based tracking (e.g. triangulation) and 150 meters for handset-based tracking (e.g. GPS). This can be especially useful when dialing an emergency telephone number, such as enhanced 9-1-1 in North America, so that the operator can dispatch emergency police or firefighting services to the correct location.

This article uses material from the Longitude article.

 
Longitude

Longitude, sometimes denoted by the Greek letter λ, describes the location of a place on Earth east or west of a north-south line called the Prime Meridian. Longitude is given as an angular measurement ranging from 0° at the Prime Meridian to +180° eastward and −180° westward. Unlike latitdue (see above), which has the equator as a natural starting position, there is no natural starting position for longitude and, therefore, a reference meridian had to be chosen. In 1884, the International Meridian Conference adopted the Greenwich meridian as the universal prime meridian or zero point of longitude.

A specific longitude may then be combined with a specific latitude (see above) to give a precise position on the Earth's surface.

This article is licensed under the GNU Free Documentation License. It uses material from the Longitude article.

 
Magnetic Declination

The magnetic declination at any point on the Earth is the angle between the local magnetic field and true north. The declination is positive when the magnetic north is east of true north.

Magnetic declination varies both from place to place, and with the passage of time. As a traveller cruises the east coast of the United States, for example, the declination varies from 20 degrees west (in Maine) to zero (in Florida), to 10 degees east (in Texas), meaning a compass adjusted at the beginning of the journey would have a true north error of over 30 degrees if not adjusted for the changing declination.

The iPointer Platform automatically corrects the compass reading for magnetic declination.

NOAA offers an online magnetic declination calculator based on the International Geomagnetic Reference Field Model.

This article is licensed under the GNU Free Documentation License. It uses material from the Magnetic Declination article.

 
NMEA

NMEA 0183 (or NMEA for short) has been defined and is controlled by the US based National Marine Electronics Association. The NMEA 0183 protocol is a means by which marine instruments and also most GPS receivers can communicate with each other. Most GPS receivers can output an NMEA string and most GPS softwares can read this string. The iPointer client also supports NMEA which makes it compatible with most GPS receivers.

The NMEA 0183 standard uses a simple ASCII, serial communications protocol that defines how data is transmitted in a "sentence" from one "talker" to one or more "listeners". The standard also defines the contents of each sentence (message) type so that all listeners can parse messages accurately:

    •    Each message starting character is a dollar sign.

    •    The next first five characters identify the type of message.

    •    All data fields that follow are comma-delimited.

    •    The first character that immediately follows the last data field character is an asterisk.

    •    The asterisk is immediately followed by a two-digit checksum.

Example of sentence:

Waypoint Arrival Alarm

$GPAAM,A,A,0.10,N,WPTNME*43

Where:

AAM    Arrival Alarm
A      Arrival circle entered
A      Perpendicular passed
0.10   Circle radius
N      Nautical miles
WPTNME Waypoint name
*43    Checksum data

The new standard, NMEA 2000, accommodates several "talkers" at a higher baud rate, without using a central hub.

The NMEA standard is proprietary and expensive. However, much of it has been reverse-engineered from public sources and is available in references like this one from <link to NMEA by Glenn Baddeley>Glenn Baddeley</link> or <link to NMEA_2>this one</link>.

This article is licensed under the GNU Free Documentation License. It uses material from the NMEA article.

 
Oracle Spatial & Oracle Locator

The location features in Oracle Database 10g provide a platform that supports a wide range of applications—from automated mapping/facilities management and geographic information systems (GIS), to wireless location services and location-enabled e-business. The Oracle Database 10g, Oracle Application Server 10g, and Oracle E-Business Suite include and make use of location features to deliver unique business advantages to users.

Through Oracle Spatial and Oracle Locator, geographic and location data are managed in a native type within Oracle Database 10g. Oracle Locator is a feature of Oracle Database 10g Standard and Enterprise Editions that provides core location functionality needed by most customer applications to support a variety of location-based services (LBS) and 3rd party GIS solutions. Oracle Spatial is an option for Oracle Enterprise Edition that provides advanced spatial features to support high-end GIS and LBS solutions. Oracle MapViewer is an Oracle Application Server Java component and JDeveloper extension used for map rendering and viewing geospatial data managed by Oracle Spatial or Locator.

Oracle Spatial and Oracle Locator have been adopted as the preferred location platform by leading GIS and LBS vendors. Oracle Spatial and Oracle Locator have also been deployed by telecommunications, utilities, and government organizations worldwide. Oracle Spatial and Oracle Locator comply with the OGC Simple Features for SQL Specification, Types and Functions Alternative.

Oracle Locator Example Functions

    •    Query nearest neighbor and other spatial relationships between geometries

    •    Perform location queries on relational information not stored in Oracle Spatial geometry

    •    Support long transactions

    •    Store and index vector geometries in the database

    •    Enhance application performance

Oracle Spatial Only Functions

    •    Everything that Oracle Locator does, and:

    •    Perform length and area calculations on geometries

    •    Generate new geometries such as buffers and unions

    •    Perform coordinate systems transformations, for individual geometries or entire layers

    •    Store linear measure information

The iPointer platform utilizes functionalities of Oracle Locator.

Source: Oracle Spatial & Oracle Locator: Location Features for Oracle Database 10g, Oracle Spatial Locator Features

What about white papers?

Oracle Locator and Oracle Spatial Option, Racle Locator: Location-Enabling Every Oracle Database, Oracle Spatial 10g

 
PL/SQL

PL/SQL is Oracle's procedural extension to industry-standard SQL. PL/SQL naturally, efficiently, and safely extends SQL. Its primary strength is in providing a server-side, stored procedural language that is easy-to-use, seamless with SQL, robust, portable, and secure. Thus, it offers a platform for robust, high-performing enterprise applications, not only for Fortune 500 customers, but also for Oracle Applications, which have over 4 million lines of code. Server-side PL/SQL needs no explicit installation or licensing. It is an implicit part of the Oracle Database and is documented as such.

PL/SQL stored procedures (functions, procedures, packages, and triggers) get compiled into an Oracle database: to this extent their SQL code can undergo syntax-checking. Programmers working in an Oracle database environment can construct PL/SQL blocks of such functionality to serve as procedures.

The iPointer Platform uses a combination of PL/SQL procedures and Java procedures for it's proprietary Selection Algorithm.

Reference: PL/SQL

This article is licensed under the GNU Free Documentation License. It uses material from the PL/SQL article.

Point of Interest

A Point of Interest, or POI, is a specific point location that someone may find useful or interesting. The term is widely used in Cartography, especially in electronic variants including GIS, and GPS navigation software.

SOAP

Soap is a protocol for exchanging XML-based messages over a computer network, normally using HTTP. SOAP forms the foundation layer of the Web services stack, providing a basic messaging framework that more abstract layers can build on.

There are several different types of messaging patterns in SOAP, but by far the most common is the Remote Procedure Call (RPC) pattern, in which one network node (the client) sends a request message to another node (the server), and the server immediately sends a response message to the client. SOAP is the successor of XML-RPC, though it borrows its transport and interaction neutrality and the envelope/header/body structure elsewhere, probably from WDDX.

This article is licensed under the GNU Free Documentation License. It uses material from the SOAP article.

SOAP documents listed here are copyright 1998-2006 W3C (MIT,ERCIM, Keio).

 
SQL

SQL (commonly expanded to Structured Query Language is the most popular computer language used to create, modify, retrieve and manipulate data from relational database management systems. The language has evolved beyond its original purpose to support object-relational database management systems. It is an ANSI /ISO standard.

 
WAAS

The Wide Area Augmentation System (WAAS) augments the Global Positioning System (GPS), improving positional accuray to 3m and providing integrity information. WAAS consists of two geostationary staellites, transmitting correction and integrity information, and 25 ground stations. The system is developed by the Federal Aviation Administration (FDA) and the United States Department of Transportation (DOT) and serves the territory of the USA and beyond. It was initailly developed to provide more reliable and accurate positioning service for aircrafts.

EGNOS is a similar technology serving Europe and beyond.

 
WEB 2.0

O'Reilly Media coined the phrase Web 2.0 in 2004 to refer to a supposed second-generation of Internet-based services that let people collaborate and share information online in perceived new ways — such as social networking sites, wikis, communication tools, and folksonomies. O'Reilly Media, in collaboration with MediaLive International, used the phrase as a title for a series of conferences and since then it has become a popular buzzword amongst the technical and marketing communities

This article is licensed under the GNU Free Documentation License. It uses material from the Web 2.0 article.