What should you know about tracking features of your GNSS device? Everyone is familiar with GPS – a reliable and very accurate method to locate the position on the Earth. That’s what GPS tracking is about. However, if you’re choosing a GPS tracker for a vehicle, you should also take some hints below into consideration.
GNSS – Multi-system navigation
It’s not only GPS working on the orbit today, but also GLONASS and some other to go soon. If your vehicle tracker can receive signals from multiple satellite systems (all together called GNSS – Global Navigation Satellite Systems), then tracking will be more precise and reliable. It’s important, especially in urban conditions when a vehicle is surrounded by high buildings, or in the dense forest.
The Global Navigation Satellite System is a special infrastructure consisted of satellite constellations and supporting ground constructions. The main GNSS mission is providing wireless connection all around the Earth for global navigation. GNSS is used for locating people and transport, including military planes and spacecrafts.
Satellites locate GNSS trackers with the use of distance measurement between receiver and available satellites in a visible area. It is possible due to an extremely accurate position of each spacecraft (containing in special Almanac) and a principle of time synchronization.
For the correct locating process, a receiver needs at least 3 satellites, but the use of 4 spacecrafts can guarantee precise positioning results. A receiver can transmit its coordinates to the third party using GNSS connection all the same. It gives the possibility to track someone who has a receiver that is used for business, personal, military and safety purposes.
There are a few GNSS like GPS, GLONASS, Galileo and etc. You can learn more about them in our popular review.
Assisted GPS: faster positioning
Assisted GPS or also known as “A-GPS” (don’t mix with LBS!) helps to acquire the position faster. The known lack of GPS technology is a certain time which is required to obtain the coordinates after GPS device was turned off. The so-called TTFF (Time-to-The-First-Fix) lasts up to 2-3 minutes – depending on the receiving conditions of the satellite signals. Until enough data received from the satellites by a GPS receiver, it won’t be able to calculate the signal. To improve TTFF “Assisted GPS” technology is used: a significant part of the data will be downloaded from the Internet via GPRS channel. Today only the middle- and high-end GPS devices have this feature.
A-GPS is an auxiliary system uses the information from the internet networks to help the GPS devices locate itself more faster. It is useful when normal work of GNSS is hampered for some reasons.
In other words, it relates to TTFF (time-to-first-fix) parameter when GPS receiver needs some time retrieve its current position by getting necessary information from the constellation of satellites. This time period is needed to update the almanac and can last from one second in clear sky situation to 30-40 seconds in problem condition cases including long offline period, weather storms and etc.
A-GPS helps to update almanac and recognize satellite positions faster. That way, a GPS receiver can start its work faster and show good tracking quality without missing of waypoints.
A-GPS is a feature of Global Positioning System and it can’t work without a GPS antenna inside a tracker.
You can read more about A-GPS in our article.
LBS: locating assets under roofs
Using of location-based services (LBS) is an alternative way of navigation, especially indoor. It uses information about signals strength of the nearest cellular base stations and Wi-Fi hotspots to approximate object’s current location. The key function of LBS is retrieving cellular and Wi Fi identifiers and submit them to tracking server. The technology has no direct relation to any sort of GNSS (and even satellite receiver is not a must), but requires stable connection between device and Internet.
In the broad sense the term “Location Based Services” (or LBS) refer to all kind of services which use the information about the object’s position: road navigation, traffic assistance, social networks (e.g. FourSquare), geo-based advertisement, etc. However, when we apply this term to asset tracking, we consider the using of alternative to GNSS methods for acquiring the position.
Here’s how it works. LBS tracking uses the information from the nearest cellular network base stations – since GPS tracking devices are equipped with cellular module, it’s usually not a problem. After we know the nearest base stations (Cell ID, LAC, etc.) we can obtain approximate position – usually in the range of 300-500 meters (1000-1500 feet) in urban area and 500-3000 meters (1500-10000 feet) in the countryside.
In practise LBS helps to cover the “blind spots” of the GNSS, to back up the GPS/GLONASS based location. For example, when a car enters an underground parking, there are no satellite signals at all, thus LBS is the only chance to estimate its current location.
When we take smartphones equipped with WiFi modules, we can also use data from the closest WiFi spots and acquire the position in a similar way, as we did with GSM/CDMA networks, and even more precise (up to a few dozens of meters/feet).
Various tracking modes
GPS trackers can operate in different tracking modes. They can be in operational mode permanently or seldom, depending on the owner’s needs. Also, working GPS device can put a track after a covered distance, predetermined time period or zigs. More features assure a better quality of tracking.
Using a GPS device, you may track a target or yourself in different ways. First of all, all GPS trackers have continuous and interval modes. Continuous mode implies that device work permanently during a long period with all its options and features. At that, the power consumption is often high. In a case of using the interval mode, power consumption is low, because GPS tracker is switched on only for a few seconds while it stands in sleep mode the rest of the time. Some GPS devices can work in both tracking modes on the assumption of the owner’s needs
On the other hand, tracking mode is the algorithm of sending a signal that is used by GPS tracker. The base operation modes are time, distance and angle tracking modes. It means that GPS receiver will send a signal when you cover estimated distance or/and after a specific time. Angle tracking is often used in vehicle navigation when the more accurate waypoint line is required. Then GPS device reacts to changing of driving direction and put an additional waypoint on a map.
As a rule, all the tracking features are configurable for certain needs of the device owner. They are limited only by functionality of each GPS tracker.