A Comparative Review of Contour and Raster Based Methods for the Prediction of Surface Water Flow from DEM Data

A water management strategy to cope with severe climate change needs an efficient streamline model to play the important role of predicting the direction of flood-water. Generally a model is constructed using various image processing techniques which, depending on the particular area, can be quite complicated. In this paper two conceptually different approaches for determining streamlines from DEM data, in raster and vector forms, are reviewed. The advantages and limitations of both approaches are considered and compared using the numerical results of streamlines for the geometrically complex region containing Khao Luang National Park

Digital elevation modelling by radargrammetry in real-beam ground mapping mode

In this thesis the problem of estimating terrain elevation using two-dimensional radar data from the multirole ghter aircraft JAS 39 Gripen is considered. Radar data contains information about range from the aircraft to the reflecting terrain, as well as horizontal angle. In general, radar data has high resolution in range and low resolution in angle, giving rise to interesting problems. A new radar with higher resolution is in development for the next-generation Gripen. This thesis aims at answering whether estimation of terrain height can be done using available radar data, in order to evaluate the plausibility of doing this with data from the new radar. The approach is to find matching terrain features in subsequent images of the ground, and use this information to calculate terrain elevation. Two approaches are implemented and studied, both on simulated radar data and on real datasets. One approach uses Harris corner detection and the other uses Speeded-Up Robust Features (SURF). Conclusions drawn are that the algorithms do not work for the available radar data, but that they possibly could work when higher resolution data from the new radar is available

Topography analysis in wind estimation process

Povećana potražnja za energijom u svijetu, kao i sve stroži propisi i zahtjevi za zaštitom okoliša rezultirali su većim korištenjem energije vjetra, odnosno rastom izgradnje energetskih objekata koji proizvode struju iz vjetra. Proces izgradnje vjetroelektrane složen je proces koji traje više godina i uključuje brojne radnje, od planiranja, do provođenja različitih analiza. Jedna od ključnih analiza tijekom izgradnje vjetroelektrane je analiza procjene vjetropotencijala, na temelju koje se utvrđuje količina vjetra na željenoj lokaciji i samim time utvrđuje isplativost gradnje vjetroelektrane. Proces procjene vjetropotencijala također je složen proces koji obuhvaća brojne radnje, a simulacije koje se provode na temelju meteoroloških i topografskih parametara (visina, hrapavost i prepreke) mogu se izvoditi u različitim fizikalnim modelima, od kojih su najpoznatiji linearni BZ model kojeg koristi program WAsP, te sve prisutniji CFD modeli. U ovom istraživanju korišten je program WAsP na području postojeće Vjetroelektrane „Danilo“ kod Šibenika da bi se utvrdilo u kolikoj mjeri topografski parametri utječu na procjenu vjetropotencijala. Vremenski okvir meteoroloških podataka istraživanja uzet je od 1. prosinca 2015. do 1. prosinca 2016. u kojem nije bilo grešaka na mjernom stupu. Najveći dio istraživanja odnosi se na visinske podatke koji aproksimiraju stvarni reljef oko vjetroelektrane. Oni su dobiveni iz 6 različitih globalnih DEM-ova, Topografske karte 1:25.000 i Digitalnog modela visina Državne geodetske uprave Republike Hrvatske. Izohipse izdvojene iz ovih izvora podijeljene su u 4 kategorije s različitim ekvidistancama: 2,5, 5, 10 i 20 metara. Simulacije su provedene na istraživanom području radijusa 5, 10, 15 i 20 kilometara oko svih stupova Vjetroelektrane „Danilo“. Testiranjem različitih područja i visinskih podataka dobiveno je 136 kombinacija. Utvrđeno je da je procijenjena proizvodnja u prosjeku manja od stvarne proizvodnje za 12 do 15 %, ovisno o izvoru visinskih podataka. Najbolja procjena temeljena je na EUDEM modelu, dok se procjena s najvećim odstupanjem temelji na na topografskoj karti. Od testiranih područja utvrđeno je da se najbolja procjena ostvaruje na području radijusa 10 km oko vjetroelektrane. U kombinaciji modela veće i manje rezolucije utvrđeno je da modeli veće rezolucije daju bolje procjene. Kod istraživanja ekvidistance izohipsa utvrđeno je da su kod tri od ukupno šest modela najbolju procjenu dale izohipse ekvidistance 20 metara.An increased demand for energy in the World, as well as gradually more strict regulations in environmental protection have resulted in a more extensive usage of wind power and an increase in construction of energy plants that use wind to generate electricity. Construction of wind power plants is a complex process that lasts for years and includes many tasks like planning and implementing various analyses. One of the key analyses in the process of constructing a wind power plant is the analysis of wind estimation that is used to determine the amount of wind on a location and the profitability of the construction. The process of wind power estimation is also a complex process that includes many actions and the simulations performed based on meteorological and topographic parameters (altitude, roughness and obstacles) may be conducted in various physical models, like the widely known linear BZ model used by the WAsP program, as well as the increasingly used CFD models. This research applies the WAsP program in the area of the existing wind power plant “Danilo” near Šibenik, Croatia to determine the degree of influence of topographic parameters on wind estimation. The used timescale of meteorological data is December 1, 2015 to December 1, 2016, during which there were no errors on the measuring mast. Most of the research focuses on altitude data that approximate the real relief around the wind power plant. They have been extracted from 6 different global DEMs, topographic maps scaled 1:25.000 and Digital model of altitudes by the National geodetic administration of the Republic of Croatia. The contour lines singled out from these sources have been organized info 4 categories with different equidistances – 2.5, 5, 10 and 20 meters. The simulations have been conducted within the researched area with a radius of 5, 10, 15 and 20 kilometers around each turbine of the “Danilo” wind power plant. Through the testing of various areas and altitude data a total of 136 combinations have been acquired. It has been confirmed that the estimated average power generation is lower than the real power generation by 12 to 15%, depending on the source of altitude data. The most precise estimation was based on EUDEM model, while the estimation with the highest deviation was the one based on topographic map. It has been found that within the tested areas the best estimation is made for the area within the 10-kilometer radius around the wind power plant. Through combining the models with higher and lower resolution it has been determined that the models with higher resolution provide better estimations. Furthermore, in the research of contour line equidistances it has been determined that the contour lines with an equidistance of 20 meters give the best estimate in three out of six used models