Digitalni modeli terena - primarna geomorfometrijska baza podataka u GIS-u

Daljim razvojem tehnologije prikupljanja, obrade i vizuelizacije podataka o reljefu terena, DMT postaje sve više standardni produkt prikaza reljefa. Osobenosti ove baze podatka o visinama terena i njihova evidencija na računarskim medijima, omogućava da se primenom jednostavnih algoritama dođe do kvantitativnih geomorfoloških parametra. Savremeni softverski paketi za modeliranje terena, sve više uvode računanje ovih parametra kao standardne korisničke funkcije. Iz datih razloga može se očekivati da DMT sve više potiskuje ostale materijale koji se koriste u geomorfometrijskoj analizi. DMT koji je u fazi izrade na Vojno Geografskom Institutu predstavljaće nacionalnu bazu podataka o visinama za teritoriju cele Srbije i Crne Gore i svojim višenamenskim karakterom, parametrima tačnosti i dimenzijama grida, činiće dobru osnovu za geomorfometrijske analize na teritoriji cele države

Prilog istraživanju nesigurnosti digitalnih modela terena kao primarne baze podataka topografskih informacionih sistema

U radu je razmatran uticaj nesigumosti DMT-a na rezultate analiza u kojima se ova baza podataka о prostoru koristi. Za primer je izabrana kvantitativna geomorfološka analiza, odnosno izračunavanje primamih topografskih parametara, kao sto su nagib, aspekt i zakrivljenost terena. Topografski parametri kvantitativno oslikavaju teren i sami po sebi čine bazu podataka о reljefu, koja je sastavni deo Topografskih informacionih sistema (TIS). Računanje vrednosti topografskih parametara je posebno pogodno u DMT-u sa gridnom strukturom podataka. Visine terena u DMT-u su atributi tačaka, koje su osnovni entitet ovih baza. Ovakva struktura podataka DMT-a se naziva 2.5D GIS organizacijom podataka. S obzirom na tu činjenicu analiza nesigumosti DMT-a tretirana je kao ocena atributske tačnosti podataka. Kao osnovna mera tačnosti koristi se srednja kvadratna greška visina u DMT-u, dobijena na osnovu mreže kontrolnih tačaka koje su hijerarhijski veće tačnosti u odnosu na visine u DMT-u. Veoma važan podatak u analizi je i korelativna zavisnost grešaka visina u DMT-u, koja je sračunata kovarijacionom analizom reziduuma visina DMT-a i visina kontrolne mreže tačaka. Na test području "Zlatibor" za DMT dobijen digitalizacijom orohidrografskih oleata osnovne državne karte R= 1:5000 sračunate su srednja kvadratna greška visina i korelaciona dužina grešaka visina, i one iznose 1.3m i 110m, respektivno. Ovi podaci korišćeni su u daljem postupku ocene nesigumosti DMT-a na test području "Zlatibor". U radu su primenjene dve metode za ocenu kvaliteta DMT-a. Prva se zasniva na Monte Karlo metodi stohastičkih simulacija polja grešaka sa srednjom kvadratnom greškom visine i korelacionom dužinom kao ulaznim parametrima. Tako generisana polja grešaka, koja su istih dimenzija i rezolucije kao polazni grid, dodaju se na njega. Na taj način se dobijaju moguée realizacije DMT-a iz kojih se statističkom obradom dobijaju podaci о najverovatnijim vrednostima topografskih parametara i njihovim standardnim greškama za svaku ćeliju grida. U radu je pokazano da se sa relativno malim brojem generisanih simulacija (25) mogu dobiti statistički pouzdani podaci. Druga metoda je analitički postupak ocene nesigumosti DMT-a i zasniva se na Gausovom zakonu о prenosu grešaka. Metoda se svodi na teorijsko izvođenje za greške funkcija topografskih parametara. Praktičan problem koji nastaje uzimanjem u obzir korelisanosti grešaka visina, prevaziđen je jednostavnim numeričkim rešenjem. Rezultati dobijeni na ovaj način potvrđeni su poređenjem sa rezultatima dobijenim stohastičkim simulacijama. Primenom standardnih statističkih postupaka potvrđen je visok stepen saglasnosti rezultata dobijenih ovim metodama, i to za sve topografske paramétré. U radu je posebno razmatran projektni pristup određivanja kontrolnih mreža tačaka u cilju dobijanja pouzdanih rezultata koji su potrebni za ocenu kvaliteta DMT-a. Na jednom klasičnom GIS upitu, kao što je analiza dogledanja terena, pokazano je kakav uticaj može imati nesigumost DMT-a, i kako se taj uticaj može prikazati pomoću karata verovatnoéa, i u drugim primenama DMT-a. DMT sa gridnom strukturom podataka predstavlja pogodnu bazu za proračune kao sto su geomorfometrijske analize. Međutim, njihov glavni nedostatak je ograničena mogućnost nadogradnje u kvalitativnom smislu. Primenom kokriging geostatističke interpolatone metode u radu je prikazano moguće rešenje ovoga problema sa zadovoljavajućim rezultatom. Sa relativno malim brojem naknadno merendi tačaka na terenu (156 tačaka) srednja greška visina u polaznom DMT-u je sa 1.3077? svedena na 1.22m.This work deals with the influence of DTM's uncertainty on the results of analysis where this kind of spatial data base is used. Geomorphometric analysis, more exactly calculation of primary topographic indices (parameters), like slope, aspect and curvature of the terrain, were chosen as a case study. Topographic indices are quantitative characteristics of terrain and they are also a data base of relief, which is a segment of Topographic Information System (TIS). Estimation of the topographic indices is especially suitable with grid DTM's, called digital elevation models (DEM). Terrain heights are attributes of points as basic entities in this kind of spatial date bases. This kind of data structure is well known as 2.5D GIS data bases. In respect to this, uncertainty assessment of DTM is treated as attribute accuracy estimation. A standard deviation of height error is used as a basic accuracy measure, and it is obtained from control network points which are more accurate than in DTM's heights. Very important information in this kind of analysis is correlation dependence of height errors, obtained by covariance analysis of DTM heights and residuums of control point. For DTM obtained by digitalization of contours layer of Base State Map (S = 1:5000) at test area "Zlatibor", standard deviation of height error and correlation distance were calculated to be 1.30m and 110m, respectively. These data have been used in the further procedure of uncertainty assessment of DTM's on the same test area. Two methods for DTM quality assessment were used in this work. The first one is based on the Monte Carlo method of stochastic simulations of error fields, with standard deviation of height error and correlation distance as entry parameters. The error fields, generated by this way, and which are of the same dimension and resolution as the initial grid, were added to it. Thus, the possible realizations of DTM were obtained, and data related to the most probable values of topographic parameters, as well as of their standard errors for the each grid cell, were obtained by statistical data processing. It was shown in this work that with relatively small number of generated simulations (25) statistically reliable data could be acquired. Second method is analytical approach of DTM uncertainty assessment is based on Gaussian law of error propagation. This method is based on theoretical evaluation of error function of topographic parameters. The problem which arises when correlation of heights errors is taken into account could be solved by a simple numerical solution for this method of uncertainty assessment. The results obtained by this way were verified by comparing them with the ones obtained by stochastic simulations. The high level of agreement of the results obtained by these two methods, for all topographic parameters, was confirmed by standard statistical procedures The project procedure for establishing the control networks, with the aim of getting reliable results necessary for DTM quality assessment, was particularly examined in this work. The influence of DTM uncertainty, as well as the method of its presentation (probability maps) in the other DTM applications, were shown in a classical GIS query, such as a viewshed analysis

Mapping probabilities of precipitation occurrence on the territory of the Republic of Serbia by the method of indicator kriging

This paper presents the application of indicator kriging as a geostatistical method for the purpose of creating maps of precipitation occurrence probabilities on the territory of the Republic of Serbia for distinctive months during 2009. The difference between this approach to mapping and standard isohyetal maps, which describe precipitation intensity, lies in the fact that this approach points to the potential of the occurrence of a certain amount of precipitation at a specific location for a given time period. [Projekat Ministarstva nauke Republike Srbije, br. III 47014, br. TR 36009 i br. III 43007

Elements of spatial data quality as information technology support for sustainable development planning

We are witnessing nowadays that the last decade of the past century, as well as the first years of the present one, have brought technology expansion with respect to spatial data gathering and processing which makes a physical basis for management of spatial development. This has resulted in enlargement of the spatial data market. New technologies, presented in computer applications, have greatly expanded the number of users of these products. The philosophy of spatial data collecting has changed; analogue maps and plans printed on paper have been replaced by digital data bases which enable their presentation in a way that is the best for a particular user. Further, digital spatial data bases provide the possibility of their further upgrading by users. The two aspects, with respect to circumstances mentioned above, are very important in the process of data bases production and distribution. Firstly, the users of these data bases should be the ones who decide which of the available bases could satisfy their requirements, or in other words, what is the data quality level necessary for a certain application. On the other hand, the visualization of digital data bases could often mislead, since review of data bases could present data with better accuracy then the actual one. Thus, certain methods that would point to a quality of the selected data in the process of their analysis should be available to users. Specific, already adopted international standards, or specially developed procedures and methodologies, so called de facto standards, could be used in this data processing, enabling the estimation of these data quality. The development of Open GIS concept requires the adoption of widely accepted standards for spatial data quality. It is recommended that ISO standards should be accepted, firstly TC211 standards which are related to geographic information and geomatics. The realization of projects on ISO standards should be finished by 2006, so, all participants of these data bases should be both familiar with this project and ready to adapt to the given solutions. The basic components defining quality of data bases are explained by this work, and the results of the standardization regarding the procedures and methodology of their quality assessment, obtained so far, are also presented

Probability maps as a measure of reliability for indivisibility analysis

Digital terrain models (DTMs) represent segments of spatial data bases related to presentation of terrain features and landforms. Square grid elevation models (DEMs) have emerged as the most widely used structure during the past decade because of their simplicity and simple computer implementation. They have become an important segment of Topographic Information Systems (TIS), storing natural and artificial landscape in forms of digital models. This kind of a data structure is especially suitable for morph metric terrain evaluation and analysis, which is very important in environmental and urban planning and Earth surface modeling applications. One of the most often used functionalities of Geographical information systems software packages is indivisibility or view shed analysis of terrain. Indivisibility determination from analog topographic maps may be very exhausting, because of the large number of profiles that have to be extracted and compared. Terrain representation in form of the DEMs databases facilitates this task. This paper describes simple algorithm for terrain view shed analysis by using DEMs database structures, taking into consideration the influence of uncertainties of such data to the results obtained thus far. The concept of probability maps is introduced as a mean for evaluation of results, and is presented as thematic display

Elements of spatial data quality as information technology support for sustainable development planning

We are witnessing nowadays that the last decade of the past century, as well as the first years of the present one, have brought technology expansion with respect to spatial data gathering and processing which makes a physical basis for management of spatial development. This has resulted in enlargement of the spatial data market. New technologies, presented in computer applications, have greatly expanded the number of users of these products. The philosophy of spatial data collecting has changed; analogue maps and plans printed on paper have been replaced by digital data bases which enable their presentation in a way that is the best for a particular user. Further, digital spatial data bases provide the possibility of their further upgrading by users. The two aspects, with respect to circumstances mentioned above, are very important in the process of data bases production and distribution. Firstly, the users of these data bases should be the ones who decide which of the available bases could satisfy their requirements, or in other words, what is the data quality level necessary for a certain application. On the other hand, the visualization of digital data bases could often mislead, since review of data bases could present data with better accuracy then the actual one. Thus, certain methods that would point to a quality of the selected data in the process of their analysis should be available to users. Specific, already adopted international standards, or specially developed procedures and methodologies, so called de facto standards, could be used in this data processing, enabling the estimation of these data quality. The development of Open GIS concept requires the adoption of widely accepted standards for spatial data quality. It is recommended that ISO standards should be accepted, firstly TC211 standards which are related to geographic information and geomatics. The realization of projects on ISO standards should be finished by 2006, so, all participants of these data bases should be both familiar with this project and ready to adapt to the given solutions. The basic components defining quality of data bases are explained by this work, and the results of the standardization regarding the procedures and methodology of their quality assessment, obtained so far, are also presented

Primena geostatistike u prostornim analizama

During the last decade, the development of computational technique has influenced wider implementation of numerical methods in different software applications, which are oriented to processing, presentation, and analysis of spatial data. This is particularly the case for geostatistical methods, which were developed for analysis of the data, which include spatial components. Those methods provide analytical processing and description of spatial continuity, which is an important characteristic for numerous natural phenomena. Implementation of classical statistical methods does not allow the perception of spatial distribution of natural phenomena. The development GIS (Geographical Information Systems) applications, especially geostatistical modules, enabled a lot of users dealing with spatial modeling and analysis to apply them in their work.Nagli razvoj kompjuterske tehnike u toku poslednje decenije uticao je i na sve veću primenu numeričkih metoda u različitim softverskim aplikacijama koje su namenjene obradi, prezentaciji i analizi prostornih podataka. Ovo se posebno odnosi na geostatističke metode koje su razvijene za potrebe analize podataka koji u sebi sadrže prostornu komponentu. One nude mogućnost analitičke obrade i opisa prostornog kontinuiteta, što je važna karakteristika za mnoge pojave u prirodi. Primena klasičnih statističkih metoda ne omogućava nam da sagledamo u potpunosti prostorni raspored pojava koje se analiziraju. Razvoj GIS (Geografski Informacioni Sistemi) aplikacija i posebno specijalizovanih geostatističkih modula unutar njih, omogućio je velikom broju korisnika koji se bave analizom i modeliranjem prostora da koriste geostatističke metode u svom poslu

Uticaj izvora podataka na tačnost digitalnog modela terena

The overview of the contemporary data acquisition methods for Digital Terrain Models (DTM), as well as the accuracy of data provided by these methods, are given in this article. The procedure of the accuracy estimation for DTM which is produced by digitizing of topographic maps and test points obtained by GPS technology and aerophotogrammetric terrain surveying, is presented.U radu je dat pregled savremenih metoda prikupljanja podataka za potrebe izrade Digitalnih Modela Terena (DMT), kao i tačnost podataka koja ove metode obezbeđuju. Na primeru digitalnog modela dobijenog digitalizacijom kartografskog sadržaja osnovne državne karte, i terenskih merenja GPS tehnologijom i aerofotogrametrijskih merenja prikazan je postupak ocene ovakvih baza podataka o reljefu