An analytical approach to single-frequency precise point positioning (PPP) is discussed in this paper. The use of the GRAPHIC ionosphere-free linear combination that is based on single-frequency phase and code observations eliminates the ionosphere bias; however, the rank deficient Gauss–Markov model is obtained. On the basis of S-transformation we prove that the single-frequency PPP represents an unbiased estimator for station coordinates and troposphere parameters, while it presents a biased estimator for ambiguities and receiver-clock error parameters. We also show that any other particular solution on the basis of S-transformation is obtained only when the common least-squares estimation in single step is applied. The recursive least-squares estimation with parameter pre-elimination only determines the vector of unknowns as possible to transform through S-transformation, whereas the same does not hold for the cofactor matrix of unknowns. The method was validated on a set of permanent stations on a territory of Europe and Slovenia, where a centimetre precision for static and a decimetre precision for kinematic survey were obtained.
COBISS.SI-ID: 7055713
A completely automatic processing chain for orthorectification of optical pushbroom sensors is presented. The procedure is robust and works without manual intervention from the arrival of the raw satellite image to orthoimage generation. It is modularly divided in three main steps: automatic GCP extraction, geometric modelling and orthorectification. The GCP extraction step uses georeferenced vector road map as a reference and produces a file with a list of GCPs coordinates and their accuracy estimation. The usability of the method is presented by testing three RapidEye images of regions with different terrain configuration. Various tests to verify the efficiency of the procedure and to make it more robust were carried out. The geometric model achieved sub-pixel accuracy in the independent check points whereas the positional accuracy of the orthoimages was around one pixel. The proposed procedure is general and can be easily adapted to various sensors.
COBISS.SI-ID: 38502189
Geographical information is connected to everyday life in many ways. Web cartography has made geospatial data more available to the public. In the next few years, the average age of the population will be over 51 years, with more than 15% of the population over the age of 65 years. The fact that the senior population is increasing suggests that online mapping and map viewer design should be aware of the senior population%s visual restrictions, as well as restrictions of other potential map users, including colour-vision-impaired users. This paper describes the senior population%s visual restrictions that can be compared with colour-vision-impaired users and provides guidelines with regard to online mapping and map viewer design for this growing segment of the elderly population.
COBISS.SI-ID: 6602081
In order to ensure safe operation of tall industrial chimneys their verticality needs to be accurately monitored. Vertical plumbing, the classic geodetic procedure for detecting the inclination has certain drawbacks and can be replaced by modern technology if necessary. In this article we are going to propose a more general and rigorous procedure, which includes measurements that result in point clouds, and explain the processing of this type of data. In our case study we used two types of modern geodetic instruments: the most accurate total station (TPS) Leica TS30 and the terrestrial laser scanner (TLS) Riegl VZ- 400. Data acquired with these instruments were fit to a cylinder using the least squares adjustment and the results were compared. The article points out the differences between the used technologies as well as the differences between the results. During the study certain questions arose and we tried our best to explain and solve them. These included: the outlier detection and removal, the influence of large amounts of data on processing time and accuracy estimates, the influence of angle of incidence of laser beam on the chimney%s inclination. In the end the deviations from the best fitting model were investigated. The article represents a comprehensive review of the use of modern geodetic technology for solving important engineering monitoring tasks.
COBISS.SI-ID: 7179617