This project studies whether or not a digital camera can be used to evaluate colour difference or colour contrast. When characterizing a test object that changes colour over time it is not always possible to do a normal colour measurement with a spectroradiometer. The alternative could be to use film or rapid fire photography to record the changes and extract the colour data from the digital information. This project involves development of a method where spectroradiometric data of a colour chart is compared to digital data taken from photos and film of the same colour chart using Photoshop. In each measurement 22 colours have been evaluated by calculating the colour difference between a direct spectroradiometric measurement of a single colour and data taken from Photoshop of that same colour. The data is compared in the CIELAB colour space using the ?E94 metric which should faithfully represent how the human eye perceives colour difference. Three sets of measurements are made .Two sets where the spectroradiometric data is compared to data from still photos, first with photos directly from the camera and then with RAW-data from the camera. The third measurement compared the spectroradiometric data with data from a frame from a video. The results show that the 22 colours are reproduced with varying degrees of accuracy in photos and video compared to a direct measurement using a spectroradiometer. For the two photo measurements the results span from ?E94 = 0.82 for the best colour reproduction to ?E94 = 17.01 for the worst reproduction. The average deviation was ?E94 = 7.48 and ?E94 = 8.46 respectively where a colour difference of ?E94 =1.0 is considered a just noticeable difference. For video the deviation spans from ?E94 = 4.89 to ?E94 = 18.11 with an average deviation of ?E94 = 11.59. ?E94 has also been used to evaluate how the colour contrast between two different colours differ between the spectroradiometric measurement and data from Photoshop. The results show that for photos the colour contrast deviates quite a bit between the two methods. A deeper evaluation of the video method shows that as long as the contrast between two colours is small the deviation compared to the spectroradiometric measurement will also be small.

In this paper, the noise temperature of an electronic tuner is determined and its significance for the suitability of such tuners in noise parameter measurement systems discussed. The noise temperature of the tuner was found to be higher than the ambient room temperature in the laboratory and vary significantly between tuner states. For impedance states with small input reflections coefficients, the excess noise temperature is around 25 K. For some of the states with higher reflection coefficients, this figure increases, reaching around 45 K at |Γ| = 0.75. Unless accounted for, this leads to errors in noise parameter extraction when using an electronic tuner in noise parameter measurements.

Vulnerable travellers experience various problems in the transport environment. These may reduce public travel confidence and consequently lead to decreased mobility. A goal of our research is to find out how to improve the accessibility to railway travelling, especially, for persons with functional limitations. By reducing barriers, the ability of travelling would be improved, and consequently allow for more flexible travel behaviors. In order to develop a model and a method of measurement for accessibility, we (a) constructed a reference group of representative ‘typical older persons’ (65-85 years) from questionnaire data, and (b) developed an accessibility measure for persons with functional limitations. In this measure barriers have different weights for the different persons depending on their functional ability and travel behavior. This gives the probability of facing a certain barrier when travelling to a certain destination; that is, a measure of accessibility for the individual. The more weight placed on a certain barrier, the less probable it is that the particular journey will take place. These weights will be obtained in forthcoming research on the perception of a set of various travel scenarios representing barriers.

The two color one-way frequency transfer in optical fiber is an alternative method to two-way time and frequency transfer that is useful if there are unknown asymmetries in the connection. The method is possible to use in existing infrastructure and is able to coexist with data channels for example in WDM systems, which make it possible to broadcast to multiple users and enables the user to be anonymous to the time or frequency transfer. The goal is to develop a stable one-way transfer method comparable with well-established two-way methods, with a precision and accuracy comparable to readily used satellite-based methods. The recent progress in the determination of the error sources introduced by the equipment used for phase comparisons as well as results from increasing the modulation frequency is presented. It is shown how the increase in frequency also enhances the precision, and a result from real time phase stabilization is presented. Furthermore, results from the introduction of a third wavelength are presented, with experimental data over one week periods.

The fundamental and most straightforward method for high performance time and frequency transfer is the two-way technique, which is suitable when the user has access to the whole system, and when both transmission paths are equal or with a known and predictable asymmetry. Furthermore it is most practical when the numbers of users are limited and when no security concerns limit the bidirectional connectivity.

Real Time Kinematic (RTK) is a system that uses the Global Navigation Satellite Systems (GNSS) for accurate positioning in real time. The idea of RTK is to receive GNSS signals with a stationary reference at a known position and using these measurements to correct the positioning data for a rover on another site where you want to determine the coordinates. The Swedish National Transport Administration operates the Project “Stomnät i Luften (SIL)”. The project aims to create a national strategy for the RTK-based core network to achieve a more efficient process for the Transport Administration's commitments to construction projects. Within the National SWEPOS network, the distance between reference stations is typically 70 km. For example, at construction work, additional reference stations are deployed around an actual working area. The purpose of this report is to answer three main questions on how performance is affected by the combination of dense and sparse reference networks, how an optimal densification of the reference network should be designed and how accuracy is affected by the construction project spatial scale We show by simulations that the best locations of reference stations to minimize the measurement error is next to the road. A denser network means we can combine large and small triangles in the network. The best measurements are achieved when the inner triangle is given in principle all weight. In practice it may be reasonable to add some weight to even the outer triangle for robustness reasons. For small construction projects, around 5 km, the simulation shows that the vertical measurement error from the RTK system is 3 mm and an expected total vertical measurement error is around 8 mm when including the contribution from the local rover. For large construction projects, about 70 km, the corresponding values are 5 mm and 9 mm respectively For these situations, there is much to gain in accuracy if the installation of the rover can be done in a way that the “local effects”, such as reflections and partial blockage is minimized . The contributions from the local effects will, however, vary greatly depending on the particular position and assembly. For regional construction projects the vertical measurement error from the RTK system is 10 mm and an expected total vertical measurement error is around 12 mm.

A part of the atmosphere is ionized by the UV radiation from the Sun. This part is often referred to as the ionosphere. The resulting free electrons influence the GNSS signals as they propagate through the ionosphere. We have studied how the spatial variations of electron density in the ionosphere affect measurements with network-RTK. The aim is to predict what we can expect from measurements during the next solar maximum that is expected to occur around 2012. In order to perform a spatial characterization of the ionosphere, we have used archived GPS data from SWEPOS from a five year period, 1999-2004, around the previous solar maximum. We find that the effect of the ionospheric spatial variability on network-RTK measurements is greater during night time than during day time. It is also clear that the effect is larger for northern Sweden than for the southern part. This is especially true during night time. The effect is also largest in the months October and November and smallest in June and July. Also the number of cycle slips is larger in northern Sweden than in southern Sweden. We find that when monitoring the ionosphere and its influence on network-RTK performance it is desirable to have several different geographical regions under observation. The effects in northern Sweden may, for example not be that relevant for a user in southern Sweden. In this report we define the ionospheric delay errors as the standard deviation of the difference between the ionospheric delay at L1 at one location and the estimated value of this based on the three surrounding reference stations with 70 km separation. Using GNSS equipment that is state-of-the art around 2010, we find that when conditions are such that the ionospheric delay error is below 10 mm, which occurs some 70% of the time, a rover is able to fix the ambiguities more than 90% of the time. This ability decreases with increasing ionospheric variability and when the ionospheric delay error is larger than 25 mm, which occurs some 10% of the time, the rover ability to fix is less than 50%. When measuring with network-RTK during the next solar maximum, approximately, 80% of the time, we have conditions such that a rover has at least 75% chance of fixing the solutions. Overall the probability to find a correct fix solution when performing RTK measurements during the next solar maximum is approximately 85% and the mean time to fix is 55 seconds.

Travelling Ionospheric Disturbances (TIDs) appear as Medium-Scale TIDs at mid-latitudes and as polar cap patches at high latitudes. Both can have a negative impact on GNSS measurements although the amplitude is of tenths of a TECU. Due to their spatial extension they affect GNSS measurements using receivers separated with distances up to ~1000 km. We present statistical measures of the ionospheric spatial variability as functions of time in solar cycle, annual season, and time of day for different geographical locations in Europe. In order to perform this spatial characterization of the ionosphere, we have used archived GPS data from a thirteen year period, 1999-2011, covering a complete solar cycle. We find that the ionospheric spatial variability is larger for the northern areas than for the southern areas. This is especially pronounced at solar maximum. For the more northern areas, the ionospheric variability is greater during night time than during day time, while for central Europe the variability is larger during day time. At solar maximum, the variability is larger during the months October and November and smaller in June and July.

This report investigates the feasibility of using smartphones as wireless reflector tags. A smartphone communicates its GNSS positioning data via peer-to-peer connections to nearby road users to notify its presence. Appropriate use cases are studied based on accident data. Different communication protocols and a pseudo differencing positioning technique are evaluated. Possibilities and obstacles are presented.

In the European Joint Research Project “Multidimensional reflectometry for industry”, a new gloss scale has been developed with the aim to represent different levels of gloss, hue, roughness and refractive indices. In this paper, the surfaces of six selected samples have been thoroughly investigated using various measuring techniques in order to verify the outcome of the novel manufacturing processes in terms of distinct levels as well as types of surface roughness. The aim of the evaluation was to capture surface structures in different wavelength intervals utilizing a confocal microscope, a coherence scanning interferometer and an atomic force microscope. Also, PSD functions calculated from the measurements have been used to determine suitability of techniques for different roughness scales. Measurements show the expected surface characteristics as well as different rms roughness values intimately connected to the perceived glossiness.

In a suggested radio propagation experiment using a deep space antenna, accurate calibration of the propagation delay through the Earth's atmosphere is essential. One or two microwave radiometers can be used for this purpose. Differences in precise locations of the radiometer(s) and antenna to be calibrated leave a residual wet path delay value. We computed the Allan Standard Deviation (ASD) of this residual, as well as the one resulting from different pointing positions in the plane of the sky, by simulations. Pointing offsets, e.g., to avoid solar radiation into the radiometer beam, lead in general to an increased ASD. However, for many observation geometries a deliberate pointing offset can compensate for the location differences. In the case studied we found a reduction of the ASD with up to 45% compared to the ASD obtained for a zero pointing offset. The size of the calculated ASD depends strongly on the model parameters used, e.g., the turbulence strength parameter Cn 2, which has a significant natural variation over a year.

A single flange 2-port TRL calibration and measurement setup for accurate THz S-parameter characterization of integrated membrane circuit devices is proposed. The proposed setup facilitates shorter access waveguides, which greatly improves the calibration uncertainty.

This paper describes a single flange 2-port measurement setup for S-parameter characterization of waveguide integrated devices. The setup greatly reduces calibration and measurement uncertainty by eliminating vector network analyzer (VNA) extender cable movement and minimizing the effect of waveguide manufacturing tolerances. Change time of standards is also improved, reducing the influence of VNA drift on the uncertainty. A TRL calibration kit has been manufactured and measurements are demonstrated in WR-03 (220-325 GHz).

The time transfer method of using passive listening and detection of SDH frame headers in fiberoptical networks has been presented earlier. Previous results, using commercialized equipment and commercial fiber-links, have shown that time transfer with a precision of the order of a few nanoseconds is possible over links with network distances exceeding 1100 km. The motivation of the work has been to develop an alternative and complementary time transfer method using existing infrastructure and to make it accessible to regular users of time keeping equipment. All previous reported experimental results were performed by SP Technical Research Institute of Sweden in commercial data communication networks in Sweden and Finland. This paper will report on the recent results from an experimental fiber test network implemented at the U.S. Naval Observatory. The fiber network is in a loop-back configuration with the two node elements in the same rack. The fiber link that connects the nodes is in an environmental chamber that allows a means to apply controlled fiber length fluctuations to the link. The performance of the Time Transfer Unit (TTU) was evaluated in this setting. This will be the first independent evaluation of the TTU equipment.

With the aim to achieve a new primary standard for calibration of ultra-low gas flows (leaks) the research in determination of gas density using optical refractometry has progressed, resulting in an evaluation of the stability of the prototype and a refined theoretical analysis. Furthermore, a renewed literature search has revealed more relevant work and further knowledge is gained from these papers. The assembled prototype was known to be of proportions far from optimum, however the assumption that it would be sufficient to reach applicable results was too optimistic. The conclusion is to continue with the efforts, however with a new and improved prototype and an adjusted choice of mirror parameters, and this report summarizes the work as of spring 2010.

Sp Sveriges Tekniska Forskningsinstitut har tillsammans med Informasic utvecklat en ny teknik för överföring av tid via fiberoptiska nät. Tekniken har redan väckt intresse för sammankoppling av olika nationella tidsskalor, särskilt inom Europa där avstånden är korta och fiberlänkarna många.

For decades the global positioning system (GPS) has been the only space geodetic technique routinely used for inter-continental frequency transfer applications. In the past very long baseline interferometry (VLBI) has also been considered for this purpose and the method's capabilities were studied several times. However, compared to GPS current VLBI technology only provides few observations per hour, thus limiting its potential to improve frequency comparisons. We therefore investigate the effect of combining GPS and VLBI on the observation level in order to draw the maximum benefit from the strength of each individual technique. As a test-bed for our study we use the CONT11 campaign observed in 2011. First we review the frequency transfer performance that can be achieved with independent technique-specific analyses, both with individual software packages and with the multitechnique software c5++. With this analysis approach both techniques, GPS and VLBI, show similar frequency link instabilities at the level of 10 -14 to 10 -15 (MDEV) on inter-continental baselines for averaging times of one day. Then we use the c5++ software for a combined analysis of GPS and VLBI data on the observation level. We demonstrate that our combination approach leads to small but consistent improvements for frequency transfer of up to 10%, in particular for averaging periods longer than 3000 s.

The European Metrology Research Program (EMRP) is a metrology-focused program of coordinated Research and Development (RD) funded by the European Commission and participating countries within the European Association of National Metrology Institutes (EURAMET). It supports and ensures research collaboration between them by launching and managing different types of project calls. Within the EMRP Call 2012 "Metrology for Industry", the joint research project (JRP) entitled "Multidimensional Reflectometry for Industry" (xD-Reflect) was submitted by a consortium of 8 National Metrology Institutes (NMIs) and 2 universities and was subsequently funded. The general objective of xD-Reflect is to meet the demands from industry to describe the overall macroscopic appearance of modern surfaces by developing and improving methods for optical measurements which correlate with the visual sensation being evoked. In particular, the project deals with the "Goniochromatism", "Gloss" and "Fluorescence" properties of dedicated artifacts, which will be investigated in three main work packages (WP). Two additional transversal WP reinforce the structure: "Modelling and Data Analysis" with the objective to give an irreducible set of calibration schemes and handling methods and "Visual Perception", which will produce perception scales for the different visual attributes. Multidimensional reflectometry involves the enhancement of spectral and spatial resolution of reference gonioreflectometers for BRDF measurements using modern detectors, conoscopic optical designs, CCD cameras, line scan cameras, and modern light sources in order to describe new effects like sparkle and graininess/coarseness. More information and updated news concerning the project can be found on the xD-Reflect website http://www.xdreflect.eu/.

SP Technical Research Institute of Sweden has previously presented results with a two color one-way method. This method is an alternative method to two-way time and frequency transfer that is useful if there are unknown asymmetries in the connection. The method is possible to use in existing infrastructure and is able to coexist with data channels for example in WDM systems, which make it possible to broadcast to multiple users and enables the user to be anonymous to the time or frequency transfer. This paper will present the results from the analysis when implementing the technique in an urban commercial optical fiber data communication WDM network between two clock labs in Sweden connecting two cesium clocks to each other for frequency comparison. The evaluation is performed with two wavelengths 8 nm apart on 6 km of installed fiber in an urban city network. The transmitter and the receiver are installed in an electromagnetically shielded room several meters below ground, and the fiber runs to a building at a distance of 3 km, and then back again. The comparison will be within the laboratory, eliminating any errors from a reference system. Results and conclusion from this evaluation reveals the propagation delay variations in the propagation distance and will display the need of compensation for these variations.

Analysis of Simulated and Real Data

Real Time Kinematic (RTK) is a system that utilises Global Navigation Satellite Systems (GNSS) to provide accurate positioning in real time. The contribution of the troposphere, the ionosphere and local effects, such as receiver noise and multipath are the most significant error sources affecting network RTK measurements We show how measurements with network RTK are affected by these different error sources under varying circumstances such as time of year or time of the day, network infrastructure, satellite systems and processing techniques We find that, for Scandinavian conditions, the effect of the ionospheric spatial variability on network RTK measurements is greater during nighttime than during daytime. The effect is also largest in the months October and November and smallest in the months of June and July. A densification of the reference network from 70 km to 35 km between the reference stations results in improved measurements. The error in the measured vertical position coordinate is reduced from 26 mm to 17 mm. The access to new GNSS reduces error in the measured vertical position coordinate from 26 to 21 mm. By using the L3-combination, the contribution from the ionosphere is reduced to virtually zero. However, this has been at the expense of the local errors