question: How does a tracking device like a Garmin watch or Strava mob app know what elevation you are, no matter where you are?
comment: It's just GPS, because of the way it calculates your location it always knows your altitude too, not just latitude and longitude. Flat street maps just don't show it, because it's no use to you.
passages: European operators are mainly using Cell ID for locating subscribers. This is also a method used in Europe by companies that are using cell based LBS as part of systems to recover stolen assets. In the US companies such as Rave Wireless in New York are using GPS and triangulation to enable college students to notify campus police when they are in trouble. Rave Wireless and other companies with location based offerings are powered by a variety of companies, including Skyhook Wireless, AlterGeo and Xtify.
  
  Section::::Applications.:Comparison of location tracking apps for mobile devices.
   Wireless tracking uses a set of anchors that are placed around the perimeter of the tracking space and one or more tags that are tracked. This system is similar in concept to GPS, but works both indoors and outdoors. Sometimes referred to as indoor GPS. The tags triangulate their 3D position using the anchors placed around the perimeter. A wireless technology called Ultra Wideband has enabled the position tracking to reach a precision of under 100 mm. By using sensor fusion and high speed algorithms, the tracking precision can reach 5 mm level with update speeds of 200 Hz or 5 ms latency.
   Several categories of methods can be used to find the location of the subscriber. The simple and standard solution is LBS based on GPS or an alternative satellite navigation system. Sony Ericsson's "NearMe" is one such example. It is used to maintain knowledge of the exact location, however can be expensive for the end-user, as they would have to invest in a GPS-equipped handset. GPS is based on the concept of trilateration, a basic geometric principle that allows finding one location if one knows its distance from other, already known locations.
  
  Section::::Locating methods.:Self-reported positioning.
   Geographic information systems such as GIS, GPS, and GNSS, have become so widespread that the term "ground truth" has taken on special meaning in that context. If the location coordinates returned by a location method such as GPS are an estimate of a location, then the "ground truth" is the actual location on earth. A smart phone might return a set of estimated location coordinates such as 43.87870,-103.45901. The ground truth being estimated by those coordinates is the tip of George Washington's nose on Mt. Rushmore. The accuracy of the estimate is the maximum distance between the location coordinates and the ground truth. We could say in this case that the estimate accuracy is 10 meters, meaning that the point on earth represented by the location coordinates is thought to be within 10 meters of George's nose—the ground truth. In slang, the coordinates indicate where we think George Washington's nose is located, and the ground truth is where it's really at. In practice a smart phone or hand-held GPS unit is routinely able to estimate the ground truth within 6–10 meters. Specialized instruments can reduce GPS measurement error to under a centimeter.
   Many RTLS systems require direct and clear line of sight visibility. For those systems, where there is no visibility from mobile tags to fixed nodes there will be no result or a non valid result from locating engine. This applies to satellite locating as well as other RTLS systems such as angle of arrival and time of arrival. Fingerprinting is a way to overcome the visibility issue: If the locations in the tracking area contain distinct measurement fingerprints, line of sight is not necessarily needed. For example, if each location contains a unique combination of signal strength readings from transmitters, the location system will function properly. This is true, for example, with some Wi-Fi based RTLS solutions. However, having distinct signal strength fingerprints in each location typically requires a fairly high saturation of transmitters.
   There are several different digital geological compasses now available, including the listerCompass . This is based on software that bypasses the inherent inaccuracy of the 'Heading' function by recording data from the magnetometers and to the accelerometers, and then computing the orientation of the iPhone using vector algebra. The accelerometers record vibration, so the iPhone needs be held still. Since very many measurements can be made in a few seconds, statistical analysis can be applied. High variance implies scattered data, so measurement should be continued until error diminishes to an acceptable level.
   BULLET::::- location signature uses "fingerprinting" to store and recall patterns (such as multipath) which mobile phone signals are known to exhibit at different locations in each cell
  
  The first two depend on a line-of-sight, which can be difficult or impossible in mountainous terrain or around skyscrapers. Location signatures actually work "better" in these conditions however. TDMA and GSM networks such as Cingular and T-Mobile use TDOA.
  
  CDMA networks such as Verizon Wireless and Sprint PCS tend to use handset-based radiolocation technologies, which are technically more similar to radionavigation. GPS is one of those technologies.
   OpenCellID
  
  OpenCellID by Unwired Labs is a collaborative community project that collects GPS positions of cell towers and their corresponding location area identity.
  
  In April 2017, Markus Semm (EnaiKoon) transferred maintainership of OpenCelliD.org to Unwired Labs, an enterprise geolocation service provider.
  
  More than 49,000 contributors are registered with OpenCellID, contributing more than 1 million new measurements every day on average to the OpenCellID database. As of August 21, 2017 the database contained 35.5 million unique cells and 2.1 billion unique measurements.
   Cellular geolocation is less precise than by GPS, but it is available to devices that do not have GPS receivers and where the GPS is not available. The precision of this system varies and is highest where advanced forward link methods are possible and is lowest where only a single cell site can be reached, in which case the location is only known to be within the coverage of that site.
  
  An advanced forward link is where a device is within range of at least three cell sites and where the carrier has implemented timing system use.
   BULLET::::- Dating apps like Grindr
  
  BULLET::::- Recording a journey, for example to show a hiking accomplishment
  
  BULLET::::- For quantified self purposes such as fitness tracking
  
  BULLET::::- GPS drawing
  
  In January 2019, the location of her iPhone as determined by her sister helped Boston police find kidnapping victim Olivia Ambrose.
  
  Section::::Privacy.
  
  Locating or positioning touches upon delicate privacy issues, since it enables someone to check where a person is without the person's consent. Strict ethics and security measures are strongly recommended for services that employ positioning.
   F-Secure discovered that the data is transmitted to Apple twice a day and postulate that Apple is using the information to construct their global location database similar to the ones constructed by Google and Skyhook through wardriving. Nevertheless, unlike the Google "Latitude" application, which performs a similar task on Android phones, the file is not dependent upon signing a specific EULA or even the user's knowledge, but it is stated in the 15,200 word-long terms and conditions of the iPhone that "Apple and [their] partners and licensees may collect, use, and share precise location data, including the real-time geographic location of [the user's] Apple computer or device".
   BULLET::::- GPS (Global Positioning System): This happens for any device which has GPS capabilities. A smartphone with GPS capabilities and set to high accuracy mode will be likely to obtain the location data from this. GPS calculate location information from the satellite signal. It has the highest accuracy; in most Android smartphones, the accuracy can be up to 10 metres.
  
  BULLET::::- Mobile Network Location: Mobile phone tracking is used if a cellphone or wireless modem is used without a GPS chip built in.
   With control plane locating, sometimes referred to as positioning, the mobile phone service provider gets the location based on the radio signal delay of the closest cell-phone towers (for phones without GPS features) which can be quite slow as it uses the 'voice control' channel. In the UK, networks do not use trilateration; LBS services use a single base station, with a "radius" of inaccuracy, to determine a phone's location. This technique was the basis of the E-911 mandate and is still used to locate cellphones as a safety measure. Newer phones and PDAs typically have an integrated A-GPS chip.
   BULLET::::- Mozilla Location Service - an open service which lets devices determine their location based on network infrastructure like WiFi access points and cell towers
  
  BULLET::::- CellMapper - cellular coverage and tower map
  
  BULLET::::- OpenCellID - an open source project, aiming to create a complete database of Cell IDs worldwide, with their locations
  
  BULLET::::- cellidfinder - Find the coordinates of any known CellID.
  
  BULLET::::- Navizon - cloud service with API to locate wireless devices using a global database of WiFi access points and Cell-ID locations
   BULLET::::- The accompanying Landsat Thematic Mapper image shows a false-color infrared image looking down at the same area in 30-meter pixels, or picture elements, for the same coordinate points, pixel by pixel, as the elevation information.
   At times geolocation can be more deductive, as with crowdsourcing efforts to determine the position of videos of training camps, combats, and beheadings in Syria by comparing features detected in the video with publicly available map databases such as Google Earth, as practiced by sites such as Bellingcat.
  
  Section::::Standards.
   One alternative to GPS is WiFi triangulation which uses the MAC addresses of nearby wireless access points to determine position. Automatic geotagging relies on media acquisition devices that contain GPS, aGPS, or WiFi or other local positioning systems. Many camera phones are also equipped to use the methods of mobile phone tracking. 
   Developed by Michael Hurnaus, their real-time location tracking device, Tractive GPS can be used via a Smartphone application or web interface. It tracks the device's positions using GPS and transfers the data using GSM technology. It has a clip mechanism that can be attached to a collar and weighs approximately 1.4 ounces. The device can be used for animals who are 9 pounds or heavier and can be used for multiple pets. The tracker is waterproof and has an optional replacement plan. It has a geofencing feature that allows for the creation of virtual fences and sends notifications when the pet enters or exits them.
   The location of a mobile phone can be determined using the service provider's network infrastructure. The advantage of network-based techniques, from a service provider's point of view, is that they can be implemented non-intrusively without affecting handsets. Network-based techniques were developed many years prior to the widespread availability of GPS on handsets. (See for one of the first works relating to this.)
   Unique to Mount Hood, these devices could be rented for $5 at Portland-area outdoor shops and the Inn, open 24 hours a day. The units were available from the late 1980s until 2017, but advances in technology now provide superior locating information by devices such as a PLB, InReach or Spot.
  
  Groups scaling Mount Hood are recommended to carry an emergency signaling device and all climbers must register before climbing and sign out upon return.
   Hybrid positioning systems use a combination of network-based and handset-based technologies for location determination. One example would be some modes of Assisted GPS, which can both use GPS and network information to compute the location. Both types of data are thus used by the telephone to make the location more accurate (i.e., A-GPS). Alternatively tracking with both systems can also occur by having the phone attain its GPS-location directly from the satellites, and then having the information sent via the network to the person that is trying to locate the telephone. Such systems include Google Maps, as well as, LTE's OTDOA and E-CellID.
   A collection of successive snapshots from a mobile device's camera can build a database of images that is suitable for estimating location in a venue. Once the database is built, a mobile device moving through the venue can take snapshots that can be interpolated into the venue's database, yielding location coordinates. These coordinates can be used in conjunction with other location techniques for higher accuracy. Note that this can be a special case of sensor fusion where a camera plays the role of yet another sensor.
  
  Section::::Wireless technologies.
   In addition, since there is no guarantee given by individual manufacturers, it should not be assumed that the magnetometer axes, and the accelerometer axes, have been accurately aligned to the orientation of the iPhone. Professional digital compass software therefore requires a calibration procedure. As noted above, this can be attempted by comparing data from traditional compasses and a digital compass, for example by slowly rotating both compasses together on a fixed horizontal or inclined surface.
  
  There is no data that suggests digital compasses on the iPhone are subject to any measurable form of magnetic disturbance.
   A current application of AoA is in the geodesic location or geolocation of cell phones. The aim is either to comply with regulations that require cell systems to report the location of a cell phone placing an emergency (i.e., 911) call or to provide a special service to tell the bearer of the cell phone where he is. Multiple receivers on a base station would calculate the AoA of the cell phone's signal, and this information would be combined to determine the phone's location on the earth. 
   BULLET::::- Skydiving – Most commercial drop zones use a GNSS to aid the pilot to "spot" the plane to the correct position to allow all skydivers on the load to be able to fly their canopies back to the landing area.
  
  BULLET::::- Wireless networking – A technique of mapping and uploading the exact or accurate location of a wireless network is called wardriving. It uses signal-strength data from the wireless adapter and GPS to identify the location. Kismet for Linux is a widely used wardriving program.
  