In two experiments, we examine how proficient second language speakers integrate verb bias and plausibility information during online sentence comprehension. Spanish–English speakers and native English speakers read sentences in English in which a post-verbal noun phrase (NP) could be interpreted as a direct object or a sentential subject. To examine the role of verb bias, the post-verbal NP was preceded by a verb that is preferentially followed by a direct object (DO-bias verbs) or a sentential complement (SC-bias verbs). To assess the role of plausibility, the semantic fit between the verb and the post-verbal NP was either congruent or incongruent with the direct object interpretation. The results show that both second language speakers and native speakers used verb bias information to assign a grammatical role to the post-verbal ambiguous NP with small differences. Syntactic revision of an initially incorrect DO interpretation was facilitated by the presence of an implausible NP.

In recent years, global navigation satellite system (GNSS) precise point positioning (PPP) has become a standard positioning technique for many applications with typically favourable open sky conditions, e.g. precision agriculture. Unfortunately, the long convergence (and reconvergence) time of PPP often significantly limits its use in difficult and restricted signal environments typically associated with urban areas. The modernisation of GNSS will positively affect and improve the convergence time of the PPP solutions, thanks to the higher number of satellites in view that broadcast multifrequency measurements. The number and geometry of the available satellites is a key factor that impacts on the convergence time in PPP, while triple-frequency observables have been shown to greatly benefit the fixing of the carrier phase integer ambiguities. On the other hand, many studies have shown that triple-frequency combinations do not usefully contribute to a reduction of the convergence time of float PPP solutions.

This paper proposes novel GPS and Galileo triple-carrier ionosphere-free combinations that aim to enhance the observability of the narrow-lane ambiguities. Tests based on simulated data have shown that these combinations can reduce the convergence time of the float PPP solution by a factor of up to 2·38 with respect to the two-frequency combinations. This approach becomes effective only after the extra wide-lane and wide-lane ambiguities have been fixed. For this reason, a new fixing method based on low-noise pseudo-range combinations corrected by the smoothed ionosphere correction is presented. By exploiting this algorithm, no more than a few minutes are required to fix the WL ambiguities for Galileo, even in cases of severe multipath environments.

We investigate effects of prosodic cues on interpretation of ambiguous sentences containing relative clauses (RCs) in English by Spanish-speaking learners. English and Spanish differ in default preference for RC attachment: English has a weak low attachment (LA) preference (RC modifies NP2); Spanish has a stronger high attachment (HA) preference (RC modifies NP1). We conducted an interpretation task with auditorily presented stimuli to examine whether prosodic cues determine attachment. Target items were manipulated for position of break and length of RC, NP1, and NP2. For both groups, break and length are significant. For the learners, proficiency interacts with break suggesting L1 transfer: lower proficiency learners choose HA more when break points to LA; higher proficiency learners choose HA more when break points to HA. Lower proficiency learners are more likely to choose LA overall, suggesting a recency effect. Our results confirm the importance of using aural stimuli when testing interpretation of ambiguous sentences.

This study introduces a new real-time kinematic (RTK) positioning method which is suitable for baselines of different lengths. The method merges carrier-phase wide-lane, and ionosphere-free observation combinations (LWLC) instead of using pseudo-range, and carrier-phase ionosphere-free combination (PCLC), or single-frequency pseudo-range and phase combination (P1L1). In a first step, the double-differenced wide-lane ambiguities were calculated and fixed using the pseudo-range and carrier-phase wide-lane combination observations. Once the double-differenced wide-lane integer ambiguities were known, the wide-lane combined observations were regarded as accurate pseudo-range observations. Subsequently, the carrier-phase wide-lane, and ionosphere-free combined observations were used to fix the double-differenced carrier-phase integer ambiguities, achieving the final RTK positioning. The RTK positioning analysis was performed for short, medium, and long baselines, using the P1L1, PCLC, and LWLC methods, respectively. For a short baseline, the LWLC method demonstrated positioning accuracy similar to the P1L1 method, and performed better than the PCLC method. For medium and long baselines, the positioning accuracy of the LWLC method was slightly higher than those of the PCLC and P1L1 methods. In conclusion, the LWLC method provided high-precision RTK positioning results for baselines with different lengths, as it used high-precision carrier-phase observations with fixed ambiguities instead of low-precision pseudo-range observations.

Studies of the second language (L2) processing of object–subject ambiguities (OSA), where the parser must revise an initially incorrect analysis of the input, have yielded two findings that the present paper addresses. First, L2 speakers are guided more strongly by plausibility information than L1 speakers in OSA processing. Second, L2 speakers generally do not perform reanalysis in real time, and their comparably poor performance on subsequent comprehension questions suggests ultimate failure to derive a grammatical parse. Because previous studies have targeted later L2 acquirers living outside of an L2 context, the present study tested whether the above two findings hold for childhood L2 acquirers with extensive naturalistic L2 exposure, hypothesizing that these factors would engender more nativelike processing. A self-paced reading task involving two kinds of OSA construction was conducted. Sensitivity to plausibility information differed across the first language and L2 groups per construction type. Within the L2 group, there is evidence that the early childhood acquirers initiated online reanalysis. Comprehension question accuracy did not differ across participant groups, suggesting that all participants succeeded in reanalysis to the same extent. The role of age of onset in L2 processing is discussed, as is the findings’ relevance to current models of L2 processing.

This study examined whether the context immediately succeeding a heterophonic-homographic word (ht-homographic) plays a role in ambiguity resolution during voiced reading of Hebrew. A pretest was designed to find the preferred alternatives of 12 ht-homographic words: 20 adult subjects completed truncated sentences, each ending with a homographic word, preceded by a context allowing for both of its alternatives to be read. Following the pretest, each word was embedded in four research conditions determined by post-homographic context (keeping preceding context constant): two adjacent revealing contexts, one supporting the preferred alternative and the other the un-preferred alternative; and two distant revealing contexts, one supporting the preferred alternative and the other the un-preferred alternative. Four lists of 12 sentences, each including the four conditions, were then read aloud by four groups of 20 adults. Results from a generalized linear mixed-model analysis showed that the immediately succeeding context affected the deciphering of un-preferred alternatives in voiced reading. An item analysis further showed that highly preferred alternatives were less prone to the immediately succeeding context effect than slightly preferred alternatives. We conclude that the context immediately succeeding a ht-homographic word plays a role in ambiguity resolution during voiced reading, through interactions with the word’s lexical and syntactic characteristics.

The correct ambiguity resolution between reference stations is the core issue of the whole Network Real-Time Kinematic (RTK) technology. Aimed at long fixed time and low reliability of the low elevation angle satellite ambiguity resolution during the initialisation of the Network RTK system, a three-step algorithm is proposed in this paper. Firstly, the double difference wide-lane ambiguities are fixed on the basis of the Melbourne-Wubbena (MW) method. Secondly, the double difference L1 carrier phase ambiguities of the high elevation angle satellites are fixed rapidly based on the ionosphere-free combination model. Thirdly, the corresponding ambiguities of the satellites with low elevation angles are solved with restrictions from the double difference tropospheric information, which is obtained from observations of the high elevation angle satellites. Based on this algorithm, an overall scheme of the ambiguity resolution during the initialisation process of the Network RTK system is designed. Results from Global Positioning System (GPS)/Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS) data demonstrate that the three-step algorithm can reduce the ill-posed problems of the observation model effectively. Moreover, the speed and accuracy performances of the ambiguity resolution for the low elevation angle satellites using the proposed algorithm are better than those of the conventional method.

An increasing number of reference stations have been established, leading to a sharp increase in the workload of Double-Difference (DD) baseline solutions, which are not appropriate for the integrated processing of denser networks. Correlations among the ambiguities in DD models are complex, and it is difficult to get precise solutions. This paper improves the DD ambiguity resolution performance over a long baseline, using a modified strategy based on an Un-Differenced (UD) and Un-Combined (UC) model. The satellite clocks are estimated as parameters, which are properly constrained by real-time satellite clock products for improving the smoothness of ambiguities. We use data from the Earth Scope Plate Boundary Observatory to examine the presented method in Global Positioning System (GPS) networks. Our method obtained more obviously centralised distributions. The successful fixed rate was 96·4% for the DD baseline solution, and 98·4% for the UD method. The proposed strategy is appropriate for the distributed architecture of extensive systems and avoids a heavy computational burden.

The goal of the present study was to identify the cognitive processes that underlie lexical ambiguity resolution in a second language (L2). We examined which cognitive factors predict the efficiency in accessing subordinate meanings of L2 homonyms in a sample of highly-proficient, Spanish–English bilinguals. The predictive ability of individual differences in (1) homonym processing in the L1, (2) working memory capacity and (3) sensitivity to cross-language form overlap were examined. In two experiments, participants were presented with cognate and noncognate homonyms as either a prime in a lexical decision task (Experiment 1) or embedded in a sentence (Experiment 2). In both experiments speed and accuracy in accessing subordinate meanings in the L1 was the strongest predictor of speed and accuracy in accessing subordinate meanings in the L2. Sensitivity to cross-language form overlap predicted performance in lexical decision while working memory capacity predicted processing in sentence comprehension.

Fast high precision relative Global Navigation Satellite System (GNSS) positioning is very important to various applications and ambiguity resolution is a key requirement. It has been a continuing challenge to determine and fix GNSS carrier-phase ambiguity, especially for medium- and long-distance baselines. In past research, with dual-frequency band Global Positioning System (GPS), it is almost impossible for fast ambiguity resolution of medium- and long-distance baselines mainly due to the ionospheric and tropospheric effects. With the launch of the BeiDou system, triple-frequency band GNSS observations are available for the first time. This research aims to test the ambiguity resolution performance with BeiDou triple-frequency band observations. In this research, two mathematical models are compared: zenith tropospheric delay as an unknown parameter versus corrected tropospheric delay. The ambiguity resolution performance is investigated in detail with BeiDou observations. Different distance baselines are tested: 45 km, 70 km and 100 km and the performances are investigated with different elevation cut-off angles. Also the performance with BeiDou alone and combined BeiDou and GPS are compared. Experimental results clearly show that with practical observations of triple-frequency bands, ambiguity of medium- or long-distance baselines can be fixed. The results also show that: the performance of ambiguity resolution with an elevation cutoff angle of 20° is much better than that of 15°; The performance with tropospheric effect corrected is slightly better than that with tropospheric effect as an estimated parameter; Dual-frequency band GPS observations will benefit ambiguity resolution of integrated BeiDou and GPS.

This paper proposes a precise and fast direction of arrival estimation method using Global Navigation Satellite System (GNSS) carrier phase measurements. Single-epoch, single-satellite integer cycle ambiguities are reliably resolved by making use of constraints and taking advantages of antenna arrays. The algorithm shows good robustness in cases where signal interruption or corruption occurs on some antenna elements as long as four antenna elements in a non-planar array have uncorrupted observables. The algorithm is demonstrated by field tests where antenna elements are connected to multiple receivers with an external common clock. The results indicate a high success rate of single-epoch ambiguity resolution and high direction of arrival accuracy.

The average inter-station distances in most established network Real Time Kinematic (RTK) systems are constrained to around 50 km. A sparse network RTK system with an average inter-station distance of up to 300 km would have many appealing advantages over a conventional one, including a significant reduction in the development and maintenance costs. The first part of this paper introduces the key approaches for sparse network RTK positioning technology. These include long-range reference baseline ambiguity resolution and real-time kinematic ambiguity resolution for the rover receivers. The proposed method for long-range kinematic ambiguity resolution can overcome the network weaknesses through three procedures: application of the interpolated corrections from the sparse network only to wide-lane combination; searching the ambiguities of wide-lane combination; and searching L1 ambiguities with wide-lane combination and ionosphere-free observables. To test these techniques, a network including ten reference stations was created from the Ordnance Survey's Network (OS NetTM) that covers the whole territory of the United Kingdom (UK). The average baseline length of this sparse network is about 300 km. To assess the positioning performance, nine rover stations situated inside and outside the network were also selected from the OS Net™. Finally, the accuracy of interpolated corrections, the positioning accuracy and the initialization time required for precise positioning were estimated and analysed. From the observed performance of each rover receiver, and the accuracy of interpolated network corrections, it can be concluded that it is feasible to use a sparse reference station network with an average inter-station distance up to 300 km for achieving similar performance to traditional network RTK positioning. The proposed approach can provide more cost-efficient use of network RTK (NRTK) positioning for engineering and environmental applications that are currently being delivered by traditional network RTK positioning technology.

The Precise Point Positioning (PPP) concept enables centimetre-level positioning accuracy by employing one Global Navigation Satellite System (GNSS) receiver. The main advantage of PPP over conventional Real Time Kinematic (cRTK) methods is that a local reference network infrastructure is not required. Only a global reference network with approximately 50 stations is needed because reference GNSS data is required for generating precise error correction products for PPP. However, the current implementation of PPP is not suitable for some applications due to the long time period (i.e. convergence time of up to 60 minutes) required to obtain an accurate position solution. This paper presents a new method to reduce the time required for initial integer ambiguity resolution and to improve position accuracy. It is based on combining GPS and GLONASS measurements to calculate the float ambiguity positioning solution initially, followed by the resolution of GPS integer ambiguities.

The results show that using the GPS/GLONASS float solution can, on average, reduce the time to initial GPS ambiguity resolution by approximately 5% compared to using the GPS float solution alone. In addition, average vertical and horizontal positioning errors at the initial ambiguity resolution epoch can be reduced by approximately 17% and 4%, respectively.

The LAMBDA method for integer least-squares ambiguity resolution has been widely used in a great variety of Global Navigation Satellite System (GNSS) applications. The popularity of this method stems from its numerical efficiency and its guaranteed optimality in the sense of maximising the success probability of integer ambiguity estimation. In the past two decades, the LAMBDA method has been typically used in cases where the number of ambiguities is less than several tens. With the advent of denser network processing and the availability of multi-frequency, multi-GNSS systems, it is important to understand LAMBDA's performance in high dimensional spaces. In this contribution, we will address this issue using real GPS data based on the Bernese software. We have embedded the LAMBDA method into the Bernese software and compared their ambiguity resolution performances. Twelve day dual-frequency GPS data with a sampling interval of 30 s was used in the experiment, which was collected from a network of 19 stations in the Perth area of Western Australia with an average baseline length of 380 km. Different experimental scenarios were examined and tested with different observation spans, which represent the different ambiguity dimensions. The results showed that LAMBDA is still efficient even when the number of ambiguities is more than 100, and that the baseline repeatability obtained with the ambiguities resolved from the LAMBDA method agreed well with that of Bernese. Therefore, for future dense network processing, the easy-to-use LAMBDA method should be considered as an alternative to baseline-per-baseline methods as those used in e.g. the Bernese software.

Ambiguity resolution is essential for precise range determination. As it is difficult to process, a good ionospheric model is essential to get unambiguous results or to reduce time to solve the ambiguities. In this paper, a developed model to determine the differential ionospheric error to sub-centimetre accuracy is described. As a function of elevation angle and TEC, the model is applicable at any location and only requires a single frequency receiver provided the TEC over the reference station is known. It has been evaluated using real GPS measurements at spaced stations in Glasgow (UK) and Stirling (UK), where the results showed good correlation. It was found that the variance ratio and reference variance of the ambiguity resolution rate and the quality of the differential positioning solution are improved. Significant improvements of more than 50% have also been found by correcting the differential ionospheric delay in the measurements for the estimated positions.

In this paper, we propose new separated decision variables that are derived by directly using the normal distribution of each measurement error and allowing substitution of the chi-square variable of the conventional method. In the derivation of the proposed decision variables, we considered not only the related mathematical model, but also the additional unmodelled properties of GPS measurements. Using the sequential pseudo-moving-average technique, we developed a method that easily obtains the combined results of multiple epochs. To verify our proposed algorithm, we analysed its performance using real data and compared the results with those of the conventional method. Our proposed approach performs better than the conventional approach, and effectively reduces computational effort by approximately 60%. Our results demonstrate that our method achieves a solution that is as reliable as the conventional technique, while reducing the time required to only 15% of that required by the conventional technique.

Small Unmanned Aerial Vehicles (UAVs) or inexpensive airplanes, such as a Cessna single engine aircraft, require a navigation system with a cheap, compact and precise sensor. Over the past ten years, GPS receivers have begun to be used as primary or alternative navigation sensors, because their use can significantly reduce the overall system cost. This paper describes a navigation system incorporating a velocity-based attitude estimation system with an attitude determination system using multiple antennae, which was implemented and tested using a UAV. The main objective was to obtain precise attitude information using low cost GPS OEM boards and antennae. Attitude boundaries are derived from the relationship between the body frame and the wind coordinates, which are used to validate the resolved cycle ambiguity in an Euler angle domain. Angular rate based on Doppler measurements was used to exclude the degenerate pseudo-roll angle information during severe uncoordinated flight. Searching for cycle ambiguity at every epoch of the flight showed that the developed system gave reliable cycle integer solutions, although the carrier phase measurement was subject to additional errors, such as multipath, external interference, and phase centre variation. A flight test was performed using a 1/4-scale Piper J3 Cub model, CMC Allstar OEM boards, OEM AT575-70 antennae, and 700 MHz PC104 board.