FAQs

The Locata system does not interfere with normal 802.11b/g operation. Does it still consume a dedicated channel of the 2.4-Ghz spectrum (more or less than a 5-Mhz channel?)

Is a LocataLite a pseudolite?

What are other applications of Locata technology?

What is the benefit of broadcasting more than one signal from a single base station?

Do you eventually see commercial GPS receivers being able to receive and use Locata signals?

Do you need fingerprinting pre-surveys for Wi-Fi positioning before applying the Locata system?

How has Locata achieved this unique ability to replicate a GPS constellation on the ground?

The core invention which allows Locata Technology to relicate GPS on the ground is a completely new and patented synchronization method called TimeLoc.

The synchronization of transmitters is essential in an autonomous radio-location system. This is one of the critical requirements for GPS, and hence each GPS satellite contains 3 or 4 atomic clocks (See: http://en.wikipedia.org/wiki/Gps#Technical_description). TimeLoc allows LocataLite transceivers to achieve incredibly accurate timing but – for the first time ever – this can be achieved without the use of atomic clocks. There is no other technology in the world that can do this.

How accurate is positioning using a LocataNet?

Technically, Locata positioning is capable of, and regularly delivers, centimetre-level accuracy. This can vary according to the accuracy requirements of any specific application and the way a LocataNet is deployed.

Locata navigation positions are generated by a “carrier-phase single-point solution”. Locata can achieve such accuracy without requiring any external augmentation, differential correction or other information.

Survey-grade GPS technology is also able to deliver centimetre-level carrier-phase positioning, but not as a “single-point solution”. To obtain high precision from GPS, surveyors require access to a lot of other complex, additional technology (such as reference receivers, differential correction networks and communication data links) to help GPS remove the errors in their system. Survey-grade GPS receivers cost upwards of US$10,000, and therefore are not feasible for general consumer use.

In which frequency band does a LocataNet operate?

LocataNets currently operate in the 2.4 GHz Industrial, Scientific, and Medical (ISM) band. This ISM band is licence free and available worldwide. The 2.4 GHz band is used by both Wi-Fi (802.11b & g) and Bluetooth. A LocataNet can be configured to operate at other frequencies, but initially the ISM band provides a straightforward, license free, continuous frequency spectrum. Using the ISM band also allows the Locata system to co-exist with GPS signals (i.e. not jam GPS) and permits a Locata-enabled GPS receiver to simultaneously use GPS and Locata signals.

Does Locata interfere with Wi-Fi, or vice versa?

The short answer is no; however as with every other radio technology that has to share the same frequency band with other users, appropriate intelligence and configuration is required when designing and installing potentially competing networks.

Locata has gone to great lengths to ensure LocataNets can interoperate with other Wi-Fi networks without deleterious effects to either network system. In fact, LocataNets are currently deployed in open-cut mine environments where the entire mine is already covered by Wi-Fi signals.. Locata was able to prove to our mining integration partners that a LocataNet was able to be successfully deployed alongside an existing Wi-Fi network. This was an essential requirement prior to the mining systems integrator committing to further product development and technology integration.

What is the transmission power of a LocataLite?

The maximum signal power for devices in the ISM band is restricted by international regulation to +8 dBm within a 3 kHz bandwidth and to a maximum of 1 Watt. A LocataNet complies with this regulation.

What range does a LocataLite transmission cover at this power?

The range of a LocataLite signal is generally in the order of tens of kilometres however, this range is limited mainly by terrain, much the same as mobile phone systems. At this time, Locata does not recommend separation of more than 5km between LocataLites, except for specialist purposes such as military aircraft applications where higher-powered systems have been trialled with distances of up to 50 km (30 miles) between LocataLite base stations.

What if more signals are required, or there is a need to extend the range of a LocataNet?

If more signal power is needed for extended coverage, additional LocataLites can be added to a LocataNet. This is the same method used by mobile phone operators that add towers to increase coverage in a specific area. For example, to increase the signals in a local shopping mall, the mobile phone operator adds mobile phone towers near the mall. Additional LocataLites can be added in much the same way, inside or outside a LocataNet coverage area, to provide additional location signals. Locata networks could have as few as four or five LocataLites, or many hundreds or even thousands of LocataLites.

Do LocataNets transmit signals that can be deciphered by standard GPS receivers?

LocataLites transmit signals that are proprietary, but which would look very familiar to anyone who has worked in GPS receiver design. Current GPS receivers cannot, at this time, receive and decode Locata signals. The two main reasons for this are: (1) LocataNets do not transmit at the standard L1 GPS frequency (they transmit in the free 2.4GHz frequency common to devices such as Wi-Fi and Bluetooth) so current standard GPS receivers cannot use the Locata signal in the same way they use GPS signals, and (2) standard GPS receiver correlators have not yet been designed to receive Locata signals.

Both of the above limitations should evaporate in the next few years. Locata has announced the release of an Interface Control Document (ICD) in Q3 2011 that clearly describes the Locata signal structure — similar to the legacy GPS ICD or recently released Galileo documents. Locata’s ICD will allow GPS or radio receiver designers to incorporate Locata signals in their position solutions in the same way they use satellite-based signals today. Locata is aware of several major companies that are already working on receiver designs that produce a combined GPS-GLONASS-Galileo-Locata solution.

How does TimeLoc work?

The complete TimeLoc process is technically complex and is best understood by studying the Locata TimeLoc Patent (US Patent #7,616,682). The TimeLoc method is also covered in the Locata Technology Primer 2011 (add hyperlink).

Nevertheless, the following is a brief high-level description:

TimeLoc is the mechanism used to synchronize the signals between LocataLites. The unique LocataLite design utilizes a receiver within the LocataLite to track both the Master LocataLite signals as well as the signals from its own internal transmitter broadcasting co-located signals. This sets up a measurable loop which is described in detail in the Locata patent document and has been named a Time Lock Loop (TLL). By taking pseudorange and carrier phase measurements from both the master and co-located signals, the LocataLite is able to move or slew its signals to align with the Master.

TimeLoc is fundamentally based on aligning the timing (range) of the signals to correspond to the geometric distances from the receive antenna to both the Master and co-located transmit antennae. These distances are easily computed from the antenna locations derived in the survey and the broadcast as the ephemeris on the 50 bps navigation data. To synchronize the co-located signals with the Master, the LocataLite slews the signals until the single difference range between the Master and co-located signals is the geometric range. This slew is accurate to the millimeter level. In this way, the LocataLite effectively serves as its own differential correction receiver.

TimeLoc is not affected by traditional synchronization problems such as RF delays in the receiver front-end or timing delays within the receiver/transmitter hardware or components. From the Locata receiver perspective, the two transmitters are seen as completely synchronized. Once the ranging signals are synchronized, the LocataLite declares it has TimeLoc, sets its health bit to healthy, and officially joins the LocataNet. The TimeLoc method is simple, robust, and works extremely well in real world deployments, allowing synchronization at the nanosecond (or better) level.

There is no other technology in the world that can do this.

Does Locata provide a common clock that all receivers can sync with?

Yes. Locata’s current system design designates one of the LocataLite transceivers as the “master clock” and all other LocataLites and Locata receivers in the network lock to that time base. A system integrator can design the LocataNet to alternatively be “locked to GPS time” (or any other time reference) if that is required. In this way, the LocataNet can distribute UTC time, or any other time reference (e.g., an atomic clock reference) throughout the network.

Does Locata provide a local or global referenced position?

Any desired “reference frame” can be provided by the LocataNet. If the LocataLite transmit antennas are surveyed to be referenced to, say, the global WGS84 standard, then the entire LocataNet will provide that reference base. However, surveyors often have to work within a “local reference” such as a local coordinate frame often used in areas like open-cut mines. It is simple to set up the LocataNet in the same coordinate frame so that position calculations do not require conversion between different datums.

What size area can a Locata network cover?

LocataNets are being operated by our partners today in real-world situations over vastly different ranges, such as:

1. Small indoor warehouse, say 30 m x 10 m;

2. Locata’s main test facility covers 300 acres with the largest distance between LocataLite transmitters being on the order of 2.5 km;

3. Open-cut mines more than 4 km in diameter and up to 500 m deep;

4. Large industrial sites; and

5. Military deployments (in completely “GPS-denied environments”) currently about 50 km x 10 km, but soon to be expanded to 6,500 sq km.

It should be clear from the above that Locata systems can be deployed to cover literally anything from a room to a large strategic area — the network design is extremely flexible and configurable for any project.

Does LocataTech provide ranges to each LocataLite, or only a computed position?

Yes, LocataTech provides pseudorange and carrier-phase measurements to each LocataLite in view, just like GPS does for satellites in view.

Are there Doppler speeds of each LocataLite?

Unlike GPS satellites, LocataLites are designed to be stationary when deployed, so they do not present a Doppler shift (except for any shift generated by user movement, of course). This greatly simplifies the search strategy required to acquire a Locata signal because the frequency shift is inherently much smaller than what is expected from satellite-based signals. Hence, when a Locata receiver acquires just one LocataLite signal, it can almost instantly acquire all the others.

What is the update rate of the Locata position and/or individual LocataLite ranges?

In our current (mid-2011) receivers the position solution is calculated at a 10 Hz rate, but up to 50 Hz rates have been demonstrated. Our rate today is constrained in our current receivers because of restricted CPU capacity. New Locata receivers that remove this limitation will be available towards the end of this year (2011), and update rates up to 100 Hz should be achieved at that time.

The Locata system does not interfere with normal 802.11b/g operation. Does it still consume a dedicated channel of the 2.4-Ghz spectrum (more or less than a 5-Mhz channel?)

LocataNets transmit in the free global ISM band at 2.4 GHz, the same band used by Wi-Fi and Bluetooth. Locata systems transmit two simultaneous pseudorandom pulsed signals, one in the lower and one in the upper sections of the ISM band. Locata’s signals do spread over more than a single 5MHz Wi-Fi “channel.” However, all Locata devices have been designed to work to the FCC regulations for that band. An important design factor from the outset was to ensure Locata systems interoperate with Wi-Fi systems. Our networks therefore “play nice” with the myriad Wi-Fi networks that are already deployed in the real-world in which our integration partners are currently working.

Is a LocataLite a pseudolite?

No. Many experts in the industry, upon hearing that Locata networks “terrestrially replicate GPS”, immediately jump to the incorrect conclusion that Locata technology is based around a device the industry has long known as a pseudolite.

These “pseudo-satellites” were designed in the 1970′s to be just that – satellite stand-ins when the USAF needed to terrestrially test GPS-like signals before there were GPS satellites in the sky.

A pseudolite transmitter outputs a ranging signal, traditionally one of the GPS signals on, or near, the GPS frequencies. However pseudolites do not synchronize to each other, which is a critical requirement for the creation of a radiopositioning system.

A pseudolite has no knowledge of neighboring pseudolites and therefore cannot synchronize to other pseudolites. Many attempts have been made by countless companies and researchers over the years to synchronize pseudolites through the use of GPS time, cables or atomic clocks. However, in the 40+ years spanning the existence of pseudolite devices, there have been no successful commercial applications. In fact, none of the many different approaches has ever delivered a widely-accepted, real-world operational system, despite the enormous technical effort, time and money put into pseudolite development.

A LocataLite is not a pseudolite. LocataLites are “devices that generate TimeLoc”. Importantly, Locata signals are not the same as GPS or any other satellite signals. The Locata system architecture is designed to create a ground-based positioning system which is a true GPS-replica, not a ground-based test capability for a satellite system (which the pseudolites were originally designed to do). The Locata system was designed from the outset with the goal of working exactly like a satellite system, as observed by the “User Segment” – a LocataNet user sees the Locata system as a “terrestrial GPS constellation”. Put in classic GPS terms, the LocataNet handles both the Space segment and the Ground segment via the LocataLite transceivers and TimeLoc. A user sees a system that is a one-way ranging system providing pseudorange and carrier-phase measurements from a network of synchronized transmitters. This is exactly the same description used to describe the GPS satellite constellation.

Locata is the only technology in the world that can do this.

What are other applications of Locata technology?

Locata now allows any entity – mine, construction site, port, warehouse, airport, strategic asset — and eventually entire cities, to determine for itself the level of positioning it wishes to deploy, under its OWN LOCAL CONTROL, with complete autonomy. In other words, in any current case where GPS-style positioning is desired — but GPS is either “flaky,” inaccurate or unavailable — then Locata may supply a complementary solution.

However, Locata also represents an innovative and previously unattainable solution for many new applications formerly out of the reach of GPS-style solutions. The easiest ones to grasp are indoor applications such as automating indoor warehousing or the tracking of first responders in emergency indoor situations. But there are obviously many other applications based around providing highly-reliable and configurable positioning in GPS-occluded areas. It will be fascinating to watch the large number of innovative applications that Locata-style positioning will enable in the future — especially after the release of the Locata ICD – which will enable numerous companies to build their own Locata receiver, or Locata-based applications.

What is the benefit of broadcasting more than one signal from a single base station?

LocataLites currently transmit four PRN-style signals from each device. The signals are both spatially diverse and frequency diverse. This diversity allows Locata position solutions to use multiple signals from “substantially the same source” to view the different effects created by multipath and signal occlusion. The differences we see from these “transmission clusters” provides important information that helps Locata positioning solutions mitigate the real-world degradation effects encountered by terrestrial positioning signals. Obviously, much of this information is proprietary, and subject to protection under our patent portfolio.

Do you eventually see commercial GPS receivers being able to receive and use Locata signals?

Locata will soon be viewed by the industry as “another independent positioning constellation” that — locally — is just as important and valid as the satellite-based constellations. Locata signals are very similar to GPS signals and can therefore be incorporated into future GPS-style receivers just as easily as any other constellation — like Galileo, for instance.

Locata is aware of several major companies that are already working on designing receivers that produce a combined GPS-GLONASS-Galileo-Locata solution. Watch this space.

Do you need fingerprinting pre-surveys for Wi-Fi positioning before applying the Locata system?

No. Locata does not have anything to do with Wi-Fi-style positioning promoted by companies like Skyhook or Ekahau. We do not need any form of “fingerprinting” or updating of Wi-Fi router databases as is required by these Wi-Fi-based positioning systems.

This question actually illustrates a point of confusion bought about by the fact that Locata transmits at the same frequency as Wi-Fi. It is critical to understand that a LocataNet is a completely independent and autonomous GPS-style network that “looks just like a satellite constellation”.

Locata chose to transmit in the free Wi-Fi radio band because it guarantees that:

1. LocataNets do not interfere, in any way, with GPS (which is a huge problem for traditional “pseudolites” which transmit in the GPS L1 radio band);

2. LocataNets can be set up anywhere in the world without requiring any license or regulatory approval (just as a Wi-Fi router can be set up anywhere in the world); and

3. Locata technology has been developed from the ground up for incorporation into a vast array of professional and consumer devices — most modern communications devices already have Wi-Fi receivers built-in. So, with minimum modification these devices will also be able to use the Locata positioning signal for a position solution.

In summary: Locata transmits in the Wi-Fi band, but it is absolutely not a Wi-Fi positioning technology like Skyhook, et al.