Aleksandar Ristić

Automated data extraction from synthetic and real radargrams of district heating pipelines

The main goal of this paper is to investigate the performance of an algorithm for point extraction from hyperbolic reflections in synthetic and real Ground-Penetrating Radar (GPR) data. The real radargrams that we considered contain hyperbolic reflections due to the presence, in the surveyed area, of district heating pipelines DN250 (250mm inner diameter pipe). These are buried 88 cm deep in a soil trench, and covered by compacted sand and concrete bricks (behaton pavement). The synthetic radargrams result from the simulation of a model representing the real geometry on the location of interest. The simulation was carried out by using gprMax, ver. 3.

Spatial analysis of high-resolution urban thermal patterns in Vojvodina, Serbia

Main objective of this study was to establish a relationship between land cover and land surface temperature (LST) in urban and rural areas. The research was conducted using Landsat, WorldView-2 (WV-2) and Digital Mapping Camera. Normalised difference vegetation index and normalised difference built-up index were used for establishing the relation between built-up area, vegetation cover and LST for spatial resolution of 30 m. Impervious surface and vegetation area generated from Digital Mapping Camera from Intergraph and WV-2 were used to establish the relation between built-up area, vegetation cover and LST for spatial resolutions of 0.1, 0.5 and 30 m. Linear regression models were used to determine the relationship between LST and indicators. Main contribution of this research is to establish the use of combining remote sensing sensors with different spectral and spatial resolution for two typical settlements in Vojvodina. Correlation coefficients between LST and LST indicators ranged from 0.602 to 0.768.

Software architecture for semantically enhanced composition of geoservices in cadastral systems

This paper presents the software architecture for the composition of geoservices that are used for the discovery, access, processing and visualisation of spatial data in the cadastral systems. The architecture is based on the current standards in the field of GIS and information technologies in general. In order to solve semantic problems, the process of service composition is enhanced with the ontologies for data and services in the cadastral systems which enable (semi)automation of the composition process.

Verification of algorithm for point extraction from hyperbolic reflections in GPR data

The main goal of this paper is to determine the characteristics of an algorithm for point extraction from hyperbolic reflections in Ground-Penetrating Radar (GPR) data with different acquisition settings. Analysis is performed on a series of experimental radargrams that were collected in real conditions, on the same location. Two district heating pipes DN250 in atrench, covered by compacted sand, were scanned and the acquisition was done by using a 900MHz antenna. The pipe depth and the axial distance were measured when the trench was open. Measured dimensions were then compared with the values obtained by the algorithm.

Application of GPR for creating underground structure model of specific areas of interest

In this paper, a general procedure for creation of georeferenced underground structure model is described. It consists of standardized survey procedures and a generalized data model. The dominant survey technology in this procedure is GPR scanning. Analysis of the procedure was done on specific areas of interest (AOI). The specific AOI, on which this research is focused are levees, utilities and landslides. Survey procedures and data model for specific AOI were discussed through case studies. Case study for levee analysis was performed on flooding bank in Novi Sad, Serbia. Results included the localization of underground structure and manmade utilities (pipes) geometry, soil type identification and volumetric moisture content of a zone where permeable material was taken out from the bank. Cylindrical utilities are identified in radargrams by the specific hyperbolic shapes whose geometries contain information on the depth, radius, spatial orientation, and apparent relative permittivity of the soil surrounding the object. An efficient approach for pipe localization and wave propagation velocity based on fitted hyperbola geometries in radargrams is presented. Landslide analysis by GPR was done on the mountain Fruska Gora. Results included underground structure localization which represented status of the landslide after the first and second mitigation measures.

Applying GPR and 2D ERT for Shallow Landslides Characterization: A Case Study

We present a procedure to estimate the characteristics of small shallow landslides based on the application of ground penetrating radar (GPR) and 2D electrical resistivity tomography (ERT). Existing procedures based on either conventional or non-invasive geophysical methods, observe almost exclusively large and deep landslides. Verification has been done on a small shallow landslide in the village of Vinca, near Belgrade, Serbia. The proposed procedure is realized in two simultaneous steps. First, from high resolution raw data obtained by GPR survey, soil horizons inside and near landslide body are estimated up to 4 m deep. The rupture surface is defined and its depth is estimated at 1.7 m. Second, ERT technology confirmed and integrated the results obtained by GPR survey. Main advantages of proposed procedure are efficiency and applicability for small shallow landslides whose number and impact on environment is dominant.