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33-416: The distance between a satellite navigation receiver and a satellite can be calculated from the time it takes for a signal to travel from the satellite to the receiver. To calculate the delay, the receiver must align a pseudorandom binary sequence contained in the signal to an internally generated pseudorandom binary sequence. Since the satellite signal takes time to reach the receiver, the satellite's sequence

66-506: A 0 , … , a N − 1 {\displaystyle a_{0},\ldots ,a_{N-1}} of N {\displaystyle N} bits, i.e. A BS consists of m = ∑ a j {\displaystyle m=\sum a_{j}} ones and N − m {\displaystyle N-m} zeros. A BS is a pseudorandom binary sequence (PRBS) if its autocorrelation function , given by has only two values: where

99-543: A calculator , this raw data may indicate the particular items that each customer buys, when they buy them, and at what price; as well, an analyst or manager could calculate the average total sales per customer or the average expenditure per day of the week by hour. This processed and analyzed data provides information for the manager, that the manager could then use to help her determine, for example, how many cashiers to hire and at what times. Such information could then become data for further processing, for example as part of

132-406: A computer program or used in manual procedures such as analyzing statistics from a survey . The term "raw data" can refer to the binary data on electronic storage devices, such as hard disk drives (also referred to as "low-level data"). Data has two ways of being created or made. The first is what is called 'captured data', and is found through purposeful investigation or analysis. The second

165-410: A point-of-sale terminal (POS terminal, a computerized cash register ) in a busy supermarket collects huge volumes of raw data each day about customers' purchases. However, this list of grocery items and their prices and the time and date of purchase does not yield much information until it is processed. Once processed and analyzed by a software program or even by a researcher using a pen and paper and

198-431: A (maximal) linear feedback shift register (LFSR). Other examples are Gold sequences (used in CDMA and GPS ), Kasami sequences and JPL sequences , all based on LFSRs. In telecommunications , pseudorandom binary sequences are known as pseudorandom noise codes ( PN or PRN codes ) due to their application as pseudorandom noise . A binary sequence (BS) is a sequence

231-400: A data input sheet might contain dates as raw data in many forms: "31st January 1999", "31/01/1999", "31/1/99", "31 Jan", or "today". Once captured, this raw data may be processed stored as a normalized format, perhaps a Julian date , to make it easier for computers and humans to interpret during later processing. Raw data (sometimes colloquially called "sources" data or "eggy" data, the latter

264-492: A k-bit binary word, with the exception of the all-0s word. For example, PRBS3 = "1011100" could be generated from x 3 + x 2 + 1 {\displaystyle x^{3}+x^{2}+1} . If you take every sequential group of three bit words in the PRBS3 sequence (wrapping around to the beginning for the last few three-bit words), you will find the following 7 word arrangements: Those 7 words are all of

297-417: A more precise modeling of distance-dependent systematic errors principally caused by ionospheric and tropospheric refractions, and satellite orbit errors. More specifically, a GNSS network decreases the dependence of the error budget on the distance of nearest antenna. Pseudorandom binary sequence A pseudorandom binary sequence (PRBS), pseudorandom binary code or pseudorandom bitstream

330-442: A network of reference stations. A typical CORS setup consists of a single reference station from which the raw data (or corrections) are sent to the rover receiver (i.e., the user). The user then forms the carrier phase differences (or corrects their raw data) and performs the data processing using the differential corrections. In contrast, GNSS network architectures often make use of multiple reference stations. This approach allows

363-562: A predictive marketing campaign. As a result of processing, raw data sometimes ends up being put in a database , which enables the raw data to become accessible for further processing and analysis in any number of different ways. Tim Berners-Lee (inventor of the World Wide Web ) argues that sharing raw data is important for society. Inspired by a post by Rufus Pollock of the Open Knowledge Foundation his call to action

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396-588: A reference to the data being "uncooked", that is, "unprocessed", like a raw egg ) are the data input to processing. A distinction is made between data and information , to the effect that information is the end product of data processing. Raw data that has undergone processing are sometimes referred to as "cooked" data in a colloquial sense. Although raw data has the potential to be transformed into " information ," extraction, organization, analysis, and formatting for presentation are required before raw data can be transformed into usable information. For example,

429-520: A repetition period of 127 values. The PRBS k or PRBS- k notation (such as "PRBS7" or "PRBS-7") gives an indication of the size of the sequence. N = 2 k − 1 {\displaystyle N=2^{k}-1} is the maximum number of bits that are in the sequence. The k indicates the size of a unique word of data in the sequence. If you segment the N bits of data into every possible word of length k , you will be able to list every possible combination of 0s and 1s for

462-421: A result of this predictability, PRBS signals can be used as reproducible patterns (for example, signals used in testing telecommunications signal paths). Pseudorandom binary sequences can be generated using linear-feedback shift registers . Some common sequence generating monic polynomials are An example of generating a "PRBS-7" sequence can be expressed in C as In this particular case, "PRBS-7" has

495-601: A source. In the context of examinations, the raw data might be described as a raw score (after test scores ). If a scientist sets up a computerized thermometer which records the temperature of a chemical mixture in a test tube every minute, the list of temperature readings for every minute, as printed out on a spreadsheet or viewed on a computer screen are "raw data". Raw data have not been subjected to processing, "cleaning" by researchers to remove outliers , obvious instrument reading errors or data entry errors, or any analysis (e.g., determining central tendency aspects such as

528-442: A standard option. RTK provides accuracy enhancements up to about 20 km from the base station. This allows the units to calculate their relative position to within millimeters, although their absolute position is accurate only to the same accuracy as the computed position of the base station. For RTK with a single base station, accuracy of 8mm + 1ppm (parts per million / 1mm per km) horizontal and 15mm + 1ppm vertical relative to

561-567: Is "Raw Data Now" , meaning that everyone should demand that governments and businesses share the data they collect as raw data. He points out that "data drives a huge amount of what happens in our lives… because somebody takes the data and does something with it." To Berners-Lee, it is essentially from this sharing of raw data, that advances in science will emerge. Advocates of open data argue that once citizens and civil society organizations have access to data from businesses and governments, it will enable citizens and NGOs to do their own analysis of

594-462: Is 1575.42 MHz, which changes phase over a thousand times more often. A ±1% error in L1 carrier-phase measurement thus corresponds to a ±1.9 mm error in baseline estimation. In practice, RTK systems use a single base-station receiver and a number of mobile units. The base station re-broadcasts the phase of the carrier that it observes, and the mobile units compare their own phase measurements with

627-437: Is a binary sequence that, while generated with a deterministic algorithm , is difficult to predict and exhibits statistical behavior similar to a truly random sequence. PRBS generators are used in telecommunication , such as in analog-to-information conversion, but also in encryption , simulation , correlation technique and time-of-flight spectroscopy . The most common example is the maximum length sequence generated by

660-476: Is a network of RTK base stations that broadcast corrections, usually over an Internet connection. Accuracy is increased in a CORS network, because more than one station helps ensure correct positioning and guards against a false initialization of a single base station. A Virtual Reference Network (VRN) can similarly enhance precision without using a base station, using virtual reference stations (VRS), instead. The concept can help to satisfy this requirement using

693-668: Is called 'exhaust data', and is gathered usually by machines or terminals as a secondary function. For example, cash registers, smartphones, and speedometers serve a main function but may collect data as a secondary task. Exhaustive data is usually too large or of little use to process and becomes 'transient' or thrown away. In computing , raw data may have the following attributes: it may possibly contain human, machine, or instrument errors, it may not be validated; it might be in different area ( colloquial ) formats; uncoded or unformatted; or some entries might be "suspect" (e.g., outliers ), requiring confirmation or citation . For example,

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726-502: Is called the duty cycle of the PRBS, similar to the duty cycle of a continuous time signal. For a maximum length sequence , where N = 2 k − 1 {\displaystyle N=2^{k}-1} , the duty cycle is 1/2. A PRBS is 'pseudorandom', because, although it is in fact deterministic, it seems to be random in a sense that the value of an a j {\displaystyle a_{j}} element

759-470: Is delayed in relation to the receiver's sequence. By increasingly delaying the receiver's sequence, the two sequences are eventually aligned. The accuracy of the resulting range measurement is essentially a function of the ability of the receiver's electronics to accurately process signals from the satellite, and additional error sources such as non-mitigated ionospheric and tropospheric delays , multipath, satellite clock and ephemeris errors. RTK follows

792-442: Is independent of the values of any of the other elements, similar to real random sequences. A PRBS can be stretched to infinity by repeating it after N {\displaystyle N} elements, but it will then be cyclical and thus non-random. In contrast, truly random sequence sources, such as sequences generated by radioactive decay or by white noise , are infinite (no pre-determined end or cycle-period). However, as

825-429: Is located at a known surveyed location, often a benchmark , and the mobile units can then produce a highly accurate map by taking fixes relative to that point. RTK has also found uses in autodrive/autopilot systems, precision farming , machine control systems and similar roles. Network RTK extend the use of RTK to a larger area containing a network of reference stations. Operational reliability and accuracy depend on

858-408: The 2 k − 1 = 2 3 − 1 = 7 {\displaystyle 2^{k}-1=2^{3}-1=7} possible non-zero 3-bit binary words, not in numeric order. The same holds true for any PRBS k , not just PRBS3. Raw data Raw data , also known as primary data , are data (e.g., numbers, instrument readings, figures, etc.) collected from

891-468: The average or median result). As well, raw data have not been subject to any other manipulation by a software program or a human researcher, analyst or technician. They are also referred to as primary data. Raw data is a relative term (see data ), because even once raw data have been "cleaned" and processed by one team of researchers, another team may consider these processed data to be "raw data" for another stage of research. Raw data can be inputted to

924-457: The base station can be achieved, depending on the device.  For example, with a base station 16 km (slightly less than 10 miles) away, relative horizontal error would be 8mm + 16mm = 24mm (slightly less than an inch). Although these parameters limit the usefulness of the RTK technique for general navigation, the technique is perfectly suited to roles like surveying. In this case, the base station

957-440: The density and capabilities of the reference-station network. With network RTK, accuracy of 8mm + 0.5ppm horizontal and 15mm + 0.5 ppm vertical relative to the nearest station can be achieved, depending on the device. For example, with a base station 16 km (slightly less than 10 miles) away, relative horizontal error would be 8mm + 8mm = 16mm (roughly 5/8 of an inch). A Continuously Operating Reference Station (CORS) network

990-448: The measurements from the C/A signals and by comparing the resulting ranges between multiple satellites. The improvement possible using this technique is potentially very high if one continues to assume a 1% accuracy in locking. For instance, in the case of GPS, the coarse-acquisition (C/A) code, which is broadcast in the L1 signal, changes phase at 1.023 MHz, but the L1 carrier itself

1023-512: The number of whole cycles between the satellite and the rover and adding the phase difference. Determining the number of cycles is non-trivial, since signals may be shifted in phase by one or more cycles. This results in an error equal to the error in the estimated number of cycles times the wavelength, which is 19 cm for the L1 signal. Solving this so-called integer ambiguity search problem results in centimeter precision. The error can be reduced with sophisticated statistical methods that compare

Real-time kinematic positioning - Misplaced Pages Continue

1056-512: The one received from the base station. There are several ways to transmit a correction signal from base station to mobile station. The most popular way to achieve real-time, low-cost signal transmission is to use a radio modem , typically in the UHF Band . In most countries, certain frequencies are allocated specifically for RTK purposes. Most land-survey equipment has a built-in UHF-band radio modem as

1089-402: The same general concept, but uses the satellite signal's carrier wave as its signal, ignoring the information contained within. RTK uses a fixed base station and a rover to reduce the rover's position error. The base station transmits correction data to the rover. As described in the previous section, the range to a satellite is essentially calculated by multiplying the carrier wavelength times

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