EVALUATION AND CALIBRATION OF FIXED-WING UAV MOBILE MAPPING SYSTEM EQUIPPED WITH LIDAR AND OPTICAL SENSORS

In this paper, a mobile mapping system mounted on the UAV is presented and evaluated. The NEO3 UAV platform is an 11 kg fixed-wing designed by the MSP company. The UAV is equipped with a Riegl miniVUX-1UAV laser scanner, which is integrated with the GNSS/INS system of Applanix APX-15 UAV and two Sony Alfa 6000 cameras collecting images in the following spectrum: visible for the first camera and near-infrared for the second camera. The UAV mobile system presented is dedicated to the acquisition of multisource data for levee monitoring using active and passive remote sensing data. In this paper, the effectiveness of the ultralight laser scanner, which has not been mounted on the fixed-wing platforms so far, was verified in the experiment with respect to data density and accuracy. The example analyses were conducted using ground control points and surfaces measured with a terrestrial laser scanner and visible in point clouds obtained with a dense image matching algorithm. Analyses showed that the achieved accuracy is much related to trajectory accuracy. The final DTM created from the data collected during the float status of the GNSS measurements of the trajectory provided twice less accurate data than during fixed status (vertical error approximately 20 cm and 10 cm respectively)

MATHEMATICAL ANALYSIS OF THE ALGORITHMS USED IN MODERNIZED METHODS OF BUILDING MEASUREMENTS WITH RTN GNSS TECHNOLOGY

The use of RTN GNSS surveying technology (Real Time Kinematic Global Navigation Satellite System) for direct measurements of building structures is extremely difficult, and often impossible. Therefore, the real-time technology is supported by indirect methods of measurements. One such solution is the method of line-line intersection. Having determined the position (the coordinates) of the so-called base points on the extension of the wall faces of a building, and having calculated the coordinates of intersection of the lines of relationships between the base points, the coordinates of corners of a building structure are obtained, which are relatively unreliable. In order to increase the reliability of these coordinates, the author proposes to add an innovative solution called vector translation to the classical method of line-line intersection. This paper proves the thesis on the increased reliability of determining the coordinates of corners of buildings by conducting an appropriate mathematical analysis of these formulas, using the algorithm developed by the author. The performed analysis shows that this innovative solution results in a smaller difference between the adjusted coordinates relative to the theoretical ones, than the difference captured from the “raw” measurement results with respect to the theoretical values

‘Other’ Posts in ‘Other’ Places: Poland through a Postcolonial Lens?

Postcolonial theory has tended to focus on those spaces where European colonialism has had a territorial and political history. This is unsurprising, as much of the world is in this sense ‘postcolonial’. But not all of it. This article focuses on Poland, often theorised as peripheral to ‘old Europe’, and explores the application of postcolonial analyses to this ‘other’ place. The article draws upon reflections arising from a study of responses to ethnic diversity in Warsaw, Poland. In doing so we conclude that postcolonialism does indeed offer some important insights into understanding Polish attitudes to other nationalities, and yet more work also needs to be done to make the theoretical bridge. In the case of Poland we propose the ‘triple relation’ be the starting point for such work

Network static DGPS positioning for medium-long distances

The use of a network of reference stations instead of a single reference station allows to model some systematic errors in a region, and to increase the distance between the rover receiver and reference stations. GPS reference stations exist in some countries, and GPS observations are available for users in real-time mode and in post-processing. The paper presents DGPS post-processing positioning with the use of three reference stations at the same time. The traditional DGPS is based on one reference station. It has been shown that the accuracy of such positioning is about 1 - 2 meters, depending on the number of satellites and the value of PDOP (Position Dilution of Precision). The accuracy of DGPS positioning degrades when the distance between the rover and the receiver station is increased. The paper shows that when we use three reference stations simultaneously, we can create pseudorange corrections for a virtual reference station, located in the vicinity of an unknown station. Three reference stations give redundant observations and enable to reduce the values of some measurement errors and biases. Practical calculations and analysis of accuracy have been presented for medium-long distances between the rover station and references

Experiences of RTK positioning in hard observational conditions during Nysa Kłodzka river project

The paper presents the application of RTK technology for measuring the horizontal and vertical cross-sections of the Nysa Kłodzka River located in the southern part of Poland. GPS measurements were performed by the staff of Chair of Satellite Geodesy and Navigation of University of Warmia and Mazury in Olsztyn in cooperation with the team of the OPeGieKa Wroclaw company. The measurements had been done for 30 days during August and September 2004. Three GPS receivers were used such as two Ashtech Z-Xtreme and one Ashtech Z-Surveyor. The radiomodems Satelline of SATEL company were used for transmitting RTK corrections from a reference station to rovers. RTK measurements were being performed in very difticult observational conditions Iike in heavy shrubbery or under trees. It was excellent occasion to test reliability and accuracy of RTK positioning in practice. In general, the use of RTK technology in woodlands and rural terrain extremely improved efficiency of works, but gross errors were being occurred from time to time in very severe conditions of GPS observations due to the lack of good satellite geometry and availability

Performance of real-time network code DGPS services of ASG-EUPOS in north-eastern Poland

This paper presents the performance study results of two ASG-EUPOS system services (KODGIS and NAWGIS) carrying out real-time network code DGPS positioning. In this elaboration, basic information about the system and discussed services are presented, as well as the advantages of the code differential positioning. The accuracies of the KODGIS and NAWGIS given by the system administrator are provided and papers and presentations with local and international impact were considered. A description of the experiment and the obtained results were provided for three days of measurements taken in north-eastern Poland, near Olsztyn. The research results showed that the positioning errors achieved using the KODGIS service throughout the study exceeded values declared by the ASG-EUPOS system administrator. This service, with respect to NAWGIS, was also characterized by higher fluctuations in the determined coordinates. Moreover, the occurrence of systematic errors in the performance of both studied services was noted, whereas the weakest element of the entire ASG-EUPOS system appeared to be the data transmission to the user

Analysis of tree stand loss based on photogrammetric data for the Wilanów district in Warsaw

Niniejsza publikacja przedstawia analizę zmian drzewostanów dla obszaru warszawskiej dzielnicy Wilanów, opracowaną na podstawie danych fotogrametrycznych. Wykorzystując różne technologie fotogrametryczne: dopasowanie obrazów cyfrowych i archiwalne lotnicze skanowanie laserowe dokonano wieloczasowej analizy zmian, która pozwoliła na otrzymanie informacji o zasięgu i występowaniu drzew w dwóch badanych okresach. Nadrzędnym problemem postawionym w badaniu było uzyskanie odpowiedzi na pytanie, jak duże zmiany w zasięgu i wysokościach drzewostanów zaszły na przestrzeni lat 2012 - 2017 oraz gdzie nie występują drzewa w 2017 roku. Wytworzone numeryczne modele pokrycia terenu zostały wykorzystane do analizy zmian występowania drzewostanów dla obszaru całej dzielnicy, w tym do detekcji miejsc ubytku koron drzew. Przeprowadzona analiza zmian wykazała ubytek biomasy dla 18.2% pojedynczych drzew, w tym, zniknięcie 11.7% drzew oraz zmniejszenie wysokości (zapewne poprzez przycięcie) dla 6.5%.This publication presents the analysis of tree stands’ changes for the area of Wilanów district in Warsaw, based on photogrammetric data. Using different photogrammetric techniques, such as image matching techniques and archival airborne laser scanning, a multitemporal analysis of vegetation changes was carried out. It enabled receiving information on the range and occurrence of trees in two different periods of time. The overriding work problem was to answer the question of how noticeable changes in trees stands’ range and height occurred over 2012 - 2017. Generated digital elevation models were used for the analysis of tree stands’ changes in the Wilanów district and the detection of places with the crowns’ loss. The carried analysis of changes showed loss of biomass for 18.2% of single trees, including disappearance of 11.7% of trees and reduction in height (probably by trimming) for 6.5% of trees

Reliable Technique of GNSS/RTK Positioning under severe observational conditions

Nowadays GNSS/RTK positioning is a very efficient technique for determination of coordinates especially when it is based on permanent reference stations. It allows every land surveyor to do his work easily and efficiently. However there are some situations when the use of RTK technique makes some difficulties, especially if the GNSS receiver has no full availability for satellites. It is well know that obstructions caused by tress, buildings, power lines etc., limit satellites availability. In those situations gross errors can appear. In order to avoid misleading coordinates occurring we can use more than one receiver has no full availability for satellites. It is well known that obstructions caused by tress, buildings, power lines etc. limit satellite availability. In Those situations gross errors can appear. In Order to avoid misleading coordinates occurring we can use more than one receiver. The paper presents practical tests and description of the GNSS/RTK technology based on the simultaneous use of three different GNSS receivers for the specific control points. Three different GNSS/RTK receivers can be placed on a special mounting beam and additionally RTK positions are send in real-time to a computer. The software on the computer analyses not only the precision but also the accuracy of determined RTK positions. In effects that solution can allow obtaining reliable coordinates even if observational GNSS conditions are very severe