Global navigation satellite system (GNSS) carrier phase integer ambiguity resolution is the key to highprecision positioning and attitude determination. In this contribution, we develop new integer least-squares (ILS) theory for the GNSS compass model, together with efficient integer search strategies. It extends current unconstrained ILS theory to the nonlinearly constrained case, an extension that is particularly suited for precise attitude determination. As opposed to current practice, our method does proper justice to the a priori given information. The nonlinear baseline constraint is fully integrated into the ambiguity objective function, thereby receiving a proper weighting in its minimization and providing guidance for the integer search. Different search strategies are developed to compute exact and approximate solutions of the nonlinear constrained ILS problem. Their applicability depends on the strength of the GNSS model and on the length of the baseline. Two of the presented search strategies, a global and a local one, are based on the use of an ellipsoidal search space. This has the advantage that standard methods can be applied. The global ellipsoidal search strategy is applicable to GNSS models of sufficient strength, while the local ellipsoidal search strategy is applicable tomodels for which the baseline lengths are not too small. We also develop search strategies for the most challenging case, namely when the curvature of the non-ellipsoidal ambiguity search space needs to be taken into account. Two such strategies are presented, an approximate one and a rigorous, somewhat more complex, one. The approximate one is applicable when the fixed baseline variance matrix is close to diagonal. Both methods make use of a search and shrink strategy. The rigorous solution is efficiently obtained by means of a search and shrink strategy that uses nonquadratic, but easy-to-evaluate, bounding functions of the ambiguity objective function. The theory presented is generally valid and it is not restricted to any particular GNSS or combination of GNSSs. Its general applicability also applies to the measurement scenarios (e.g. single-epoch vs. multiepoch, or single-frequency vs. multi-frequency). In particular it is applicable to the most challenging case of unaided, single frequency, single epoch GNSS attitude determination. The success rate performance of the different methods is also illustrated.

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Integer Least-squares Theory for the GNSS Compass

This paper presents a comparison of error characteristics between time of arrival (TOA) and time difference of arrival (TDOA) processing of the linearized GPS pseudo-range equations. In particular, the relationship among dilutions of precision (DOPs), position estimates, and their error covariances is investigated. DOPs for TDOA are defined using the error covariance matrix resulting from TDOA processing. It is shown that the DOPs and user position estimate are the same for TDOA and TOA processing. The relationship of DOPs and position estimates for standard GPS positioning and double differenced processing are also given.

Comparisons of error characteristics between TOA and TDOA positioning

A method of manufacturing a silicon carbide semiconductor device having a MOS structure includes preparing a substrate made of silicon carbide, and forming a channel region, a first impurity region, a second impurity region, a gate insulation layer, and a gate electrode to form a semiconductor element on the substrate. In addition, a film is formed on the semiconductor element to provide a material of an interlayer insulation layer, and a reflow process is performed at a temperature about 700° C. or over in an wet atmosphere so that the interlayer insulation layer is formed from the film and an edge portion of the gate electrode is rounded and oxidized.

Method of manufacturing silicon carbide semiconductor device

A method for steering an agricultural vehicle comprising: receiving global positioning system (GPS) data including position and velocity information corresponding to at least one of a position, velocity, and course of the vehicle; receiving a yaw rate signal; and computing a compensated heading, the compensated heading comprising a blend of the yaw rate signal with heading information based on the GPS data. For each desired swath comprising a plurality of desired positions and desired headings, the method also comprises: computing an actual track and a cross track error from the desired swath based on the compensated heading and the position; calculating a desired radius of curvature to arrive at the desired track with a desired heading; and generating a steering command based on the desired radius of curvature to a steering mechanism, the steering mechanism configured to direct the vehicle.

Satellite based vehicle guidance control in straight and contour modes

In one embodiment, a method for generating an adaptive air interface waveform includes generating a waveform that includes a variable carrier frequency and variable bandwidth signal. The variable bandwidth signal includes one or more subcarriers that are dynamically placeable over a range of frequencies, and each subcarrier is separately modulated according to a direct sequence (DS) spread spectrum (SS) technique. The waveform has an embedded pilot usable to optimize one or more spectrum efficiencies of the waveform. A modulation constellation, a code rate, and a code length of the generated waveform are adapted according to an available spectrum and one or more sub-carrier conditions.

An adaptive air interface waveform

The attitude of a vehicle can be precisely determined using GPS (Global Positioning System) carrier phase measurements from more than two antennas attached to the vehicle with properly applied efficient integer ambiguity resolution technique. Many methods utilizing the known baseline length as a constraint have been proposed to resolve integer ambiguity in real-time manner. Three-dimensional search space is reduced to two-dimensional search space with this constraint. But there exist still strong requirements for the fast integer ambiguity resolution, which uses single epoch measurement of longer baseline. In this paper, a new constraint from the geometry of multiple baselines is derived. With this new constraint, two-dimensional search space is further reduced to one-dimensional search space.

Integer ambiguity resolution for GPS based attitude determination system

An apparatus for compensating for dispersion of an optical fiber in an optical line, which compensates for dispersion generated in the optical fiber when an optical signal produced by an optical transmitter is transmitted to an optical receiver via the optical line, is provided. The apparatus includes a dispersion compensation fiber for compensating an optical signal produced by an optical transmitter in order to predict and compensate for dispersion generated in the optical line, a dispersion compensation filter for controlling the dispersion value of the optical signal dispersion-compensated by the dispersion compensation fiber, to gain zero overall dispersion, and an optical amplifier for amplifying a signal having a dispersion value adjusted by the dispersion compensation filter and outputting the result to the optical line. Accordingly, it is easy to zero a dispersion value of an optical fiber in the optical line by regulation of the dispersion compensation fiber and filter. When the dispersion value varies with the deterioration of the optical fiber in the optical line, continuous compensation is not possible using only the dispersion compensation fiber. However, continuous compensation is easily made by adding the dispersion compensation filter.

Apparatus for compensating for dispersion of optical fiber in an optical line

A device for fixing the optical elements of an optical fiber amplifier in a packaging box comprises a central opening provided in the packaging box for making a connection with an electronic circuit, an optical fiber holder for holding the erbium doped optical fiber around the central opening, a plurality of guide supports provided in the upper and lower sides of the optical fiber holder for holding the optical isolators, wavelength division multiplexers and optical taps, and protectors provided in the left and right sides of the optical fiber holder for holding the thermocontractile tubes.

Device for fixing the optical elements of an optical fiber amplifier

An optical attenuator and process for manufacturing optical attenuators. The optical attenuator includes an optical fiber installed in a tube so as not to be influenced by a change in external circumstances, and at least one grating formed in the optical fiber, for breaking total reflection conditions by varying refractive indices of a core layer and a clad layer of the optical fiber in order to attenuate incident light during optical transmission.

Optical attenuator and method of manufacturing same

A new and fast method to fix integer ambiguity of GPS carrier phase measurement on-the-fly is proposed. The method is distinguished from other methods in that the relationship between integer ambiguities is found and used in a constraint equation for fixing integer ambiguity. Thus the method does not require positioning for every candidate and only three independent elements of the integer ambiguities are searched: the remaining dependent elements can be obtained from the constraint equation. This may greatly reduce the computational burden. Accurate relative positioning on the move also can be accomplished by adopting the proposed method. The technique is applied to two different types of real data to show its effectiveness. Experimental results show that the proposed method is fast and efficient for relative positioning of a moving user. The method may be used in areas requiring accurate positioning such as navigation and geodesy.

Chan-Sik Park

Papers

Integer ambiguity resolution for GPS based attitude determination system

Apparatus for compensating for dispersion of optical fiber in an optical line

Device for fixing the optical elements of an optical fiber amplifier

Optical attenuator and method of manufacturing same

Efficient technique to fix GPS carrier phase integer ambiguity on-the-fly