Entwicklung eines halbautomatisierten Verfahrens zur Detektion neuer Siedlungsflächen durch vergleichende Untersuchungen hochauflösender Satelliten- und Luftbilddaten

Knowledge about land use and land cover represents an important information basis for various planning applications. In particular, urban and suburban regions are subject to a high dynamic development. The detection and identification of changes is therefore an important instrument to follow and accompany the developments by planning. Here, aerial photography and, increasingly, satellite images serve as an important basis for information. The recognition and mapping of changes is still a time-consuming and cost-intensive matter which is mostly realized by visual interpretation of aerial photography and to an increasing degree of high- and ultra-high-resolution satellite images. Within the scope of the present work a new, robust and largely automated process based on a statistical change analysis is developed and presented. Basis for the data are multitemporal high-resolution satellite image data. The generated suspect areas, respectively areas of change, are supposed to function as clues in order to facilitate the process of the visual interpretation of multitemporal image datasets with regard to change mapping, since only marked areas of change have to undergo further examination. Consequently, this process can be used as a tool to ease and accelerate the updating of planning bases in general and maps in particular so far realised by visual interpretation. However, the automation of the process is not only supposed to serve the purpose of saving time and cost but also to bring the interpretation process to a higher level of objectivity. In order to improve the quality of the whole process, for the preprocessing of the image data selected methods of image processing have been integrated. Through the use of additional geo-information reference data for the automated calculation of the areas of change, a further refinement of the results can be reached. The obtained results in the first time-cut (1997-1998) can be proved and verified by a different data-take (1997-2000). To reach a convenient use and a good distribution of the developed method, the process has been implemented by means of the widespread image processing software ERDAS IMAGINE. This allows to make the developed method available for other users, since it can easily be integrated into the working environment of ERDAS IMAGINE.Das Wissen um die Landnutzung und Landbedeckung ist für planerische Anwendungsgebiete eine wichtige Informationsgrundlage. Gerade urbane und suburbane Regionen unterliegen einer hohen Entwicklungsdynamik. Das Erkennen und Aufzeigen von Veränderungen ist somit ein wichtiges Instrument um Entwicklungen zu verfolgen und planerisch zu begleiten. Luft- und zunehmend Satellitenbilder dienen hierfür als wichtige Informationsgrundlage. Das Erkennen und Kartieren von Veränderungen ist nach wie vor eine zeitaufwändige und kostenintensive Angelegenheit, die überwiegend durch visuelle Interpretation von Luft- und zunehmend auch mit hoch- und höchstauflösenden Satellitenbildern realisiert wird. In dieser Arbeit wird ein neues, robustes, weitgehend automatisiertes, auf einem statistischen Ansatz beruhendes Verfahren der Veränderungsanalyse entwickelt und vorgestellt. Die Datengrundlage bilden multitemporale, hoch auflösende Satellitenbilddaten. Die generierten Verdachts- bzw. Veränderungsflächen sollen als Anhaltspunkte fungieren, um den Prozess der visuellen Interpretation von multitemporalen Bilddatensätzen in Hinsicht auf eine Veränderungskartierung zu erleichtern, da nur als Veränderungsflächen markierte Areale einer weiteren Untersuchung unterzogen werden müssen. Das Verfahren kann somit als Werkzeug dienen, die durch visuelle Interpretation realisierte Aktualisierung von Planungsgrundlagen bzw. Kartenwerken zu erleichtern und zu beschleunigen. Die Automatisierung des Verfahrens soll jedoch nicht allein dem Zweck der Zeit- und Kostenersparnis dienen, sondern auch den Interpretationsprozess objektiver gestalten. Um die Qualität des Verfahrens zu erhöhen, werden ausgewählte Methoden der Bildverarbeitung für die Vorverarbeitung der Bilder in das Verfahren integriert. Durch das Einbinden zusätzlicher Geobasisdaten in die automatisierte Berechnung der Veränderungsflächen kann eine weitere Verbesserung der Ergebnisse erzielt werden. Die Ergebnisse, der im ersten Zeitschnitt (1997-1998) untersuchten Datensätze, werden mit Hilfe eines weiteren Zeitschnitts (1997-2000) überprüft und verifiziert. Um eine unkomplizierte Anwendung und Verbreitung der Methode zu erreichen, wurde das Verfahren mit Hilfe der weit verbreiteten Bildverarbeitungssoftware ERDAS IMAGINE realisiert. Dies ermöglicht, das Verfahren auch anderen Nutzern zur Verfügung zu stellen, da es problemlos in die Arbeitsumgebung des Bildverarbeitungssystems ERDAS IMAGINE integriert werden kan

Erfassung und Bewertung von degradierten Böden mit Fernerkundung und GIS in Nordwest-Syrien

Due to a high population growth (approx. 2.5 % p.a) the food-sector in Syria is facing in-creasing problems. An enormous increase in population results in increased demand for food. This has adversely affected the socio-economic and ecological development in the country. Intensive use of various natural resources has led to significant changes in land use pattern, especially due to use of inappropriate methods in the agricultural sector. The increasing anthropogenic pressure on the sensitive ecological structure of the respective area causes environmental damages, in particular degradation of soil characteristics. In the semi-arid and arid eco-climatic zones vast areas are facing desertification. Soil erosion through water represents the main form of land degradation in the north-west of Syria. Particularly vulnerable are the soils with a shallow or no vegetation cover, such as the soils found in the Mediterranean hills, where olives are cultivated. For this research the Afrin region, located in the northwest of Syria, was selected as study area, in order to analyse and assess the extent of degradation. For estimation of erosion the relevant parameters of the “Universal Soil Loss Equation USLE” were used. These para-meters were adapted and integrated through remote sensing and GIS. LANDSAT TM and ASTER satellite imagery of the investigated area were used for this purpose. Data were acquired at the end of the dry season. In order to achieve an accurate evaluation and high-quality comparison of multi-temporal satellite data, imagery was firstly geometrically and atmospherically corrected and then analysed. The vegetation coverage and its current de-gradation level were investigated by spectral mixture analysis (SMA). The digital elevation model (DEM) derived from ASTER data was utilized to generate the slope gradient (S) and the slope length (L). In addition to the laboratory analysis, grain size index (GSI) and SMA were used for the characterization and mapping of soil erodibility. Land-use/land-cover classification and change detection were determined by using pixel-based classification procedures (maximum likelihood classification) and post classification methods respectively. Required samples for land cover classification of the remotely sensed data were collected during the field work, in addition to the soil samples for soil analysis. The results of this study show that advanced methods of remote sensing and GIS provide powerful tools not only for a better understanding of the land use changes, but also for an accurate assessment of land degradation and desertification. This knowledge, in turn, con-tributes highly towards developing effective and appropriate management strategies for sustainable use and conservation of natural resources in the north-west of Syri

Landcover and landuse changes in the Nigerian Chad BasinQualitative and quantitative geographic analyses by evaluation of multi-temporal and multi-sensoral remote sensing data in the context of a regional geographic information system

Die Dissertation wurde im Rahmen des von der Deutschen Forschungsgemeinschaft geförderten interdisziplinären Sonderforschungsbereiches 268 "Kultur- und Sprachentwicklung im Natrurraum Westafrikanische Savanne" angefertigt. Dabei war die Kartierung und Analyse von Landbedeckungs- und Landnutzungsveränderungen in einem Ausschnitt des nigerianischen Tschadbeckens Zielsetzung vorliegender Arbeit. Trotz eines recht großen allgemeinen Interesses am Tschadsee, dem größten See Westafrikas, fällt es schwer, topographische und thematische Information über diese Region zu erlangen. Viele Zusammenhänge bezüglich seiner Vergangenheit und seiner zukünftigen Entwicklung sind bis heute nicht geklärt. Soweit Daten zur Landbedeckung und Landnutzung bereits verfügbar waren, wurden sie aufbereitet und im Rahmen des regionalen geographischen Informationssystems FirGIS strukturiert gegliedert aufgenommen. Als hauptsächliche Datenquelle wurde jedoch auf Fernerkundungsdaten der Region zurückgegriffen. Sie liefern meist die einzige großflächig vorhandene, aktuelle und vor allem multitemporale Information über das Untersuchungsgebiet. Die Auswertung der Fernerkundungsdaten erfolgte mit Methoden der digitalen Bildverarbeitung. Aktuelle und historische Luftbilder wurden visuell interpretiert und anschließend vektoriell digitalisiert. Satellitenszenen wurden vorwiegend digital direkt im Rasterdatenmodell bearbeitet. Nach der Datenaufbereitung mit verschiedenen Techniken der Bildverarbeitung erfolgte die Auswertung mittels digitaler Klassifizierung. Weitere wichtige Bearbeitungsschritte bei der Ergebnisfindung waren unterschiedliche multitemporale Darstellungsweisen, die Berechnung von Vegetationsindizes sowie Verschneidungstechniken zur Aufdeckung von Veränderungen. Die Auswertung aller Daten erfolgte nach einem einheitlichen mehrstufigen Klassifizierungssystem, das für die Verhältnisse im Tschadbecken entwickelt wurde. Die aus den Fernerkundungsdaten abgeleiteten Ergebnisse gliedern sich nach vier verschiedenen Dimensionen der Zeit. Die Ausgangsbasis bildet eine digitale aktuelle Kartierung der Landbedeckung und Landnutzung eines mehr als 3500 km² großen Ausschnittes des nigerianischen Tschadbeckens im Maßstab 1 : 25 000. Aufbauend auf der aktuellen Landnutzungskartierung wurde für einen etwa 1100 km² großen zentralen Teilausschnitt aus dem Gesamtuntersuchungsgebiet das dynamische Verhalten der Landbedeckungs- und Landnutzungseinheiten im Jahresverlauf untersucht. Dazu konnten fünf SPOT-XS-Satellitenszenen der Vegetationsperiode 1995/96 herangezogen werden. Als Zusammenfassung aus den phänologischen Analysen aller im Untersuchungsgebiet auftretenden Objekte und ihrem entsprechenden unterschiedlichen Spektralverhalten zu verschiedenen Zeitpunkten wurde eine detaillierte Landbedeckungs- und Landnutzungskartierung der Saison 1995/96 angefertigt. Sie ging aus einer komplexen hierarchischen Satellitenbildklassifizierung mit differenzierten Zuweisungsregeln hervor. Mit den Erfahrungen aus der Untersuchung zur saisonalen Dynamik wurden in einem weiteren Schritt alle für das Teiluntersuchungsgebiet zur Verfügung stehenden Satellitenszenen ausgewertet, um Erkenntnisse über interannuelle Unterschiede der zu verschiedenen Zeitpunkten aufgenommenen Satellitenszenen zu gewinnen und deren Ursachen aufzudecken. Als ideale Grundlage wurden multitemporale Vegetationsindizes verglichen, Veränderungskarten abgeleitet und Niederschlagsdaten zur Interpretation hinzugezogen. Eine 24jährige Zeitreihe der klassifizierten Vegetationsindizes ermöglicht eine zusammenfassende Interpretation. Die Auswertung historischer Luftbilder von 1957 und der Vergleich mit den Luftbildern von 1990 ermöglichte schließlich die Beurteilung langfristiger Entwicklungen im engeren Untersuchungsgebiet. Die Ergebnisse sind in Form einer historischen Karte, als Veränderungskarten und quantitativ festgehalten. Ein wichtiges Ergebnis der vorliegenden Arbeit besteht in der Strukturierung aller verwendeten Grundlagendaten zum Thema Landbedeckung und Landnutzung im Tschadbecken einschließlich seiner Nachbargebiete innerhalb des regionalen geographischen Informationssystemes FirGIS. In ihm sind neben den Ausgangsdaten alle Ergebnisse und die zum Thema gehörigen Zusatzinformationen enthalten. Es ermöglicht damit eine zukünftige Fortschreibung durch thematische, räumliche oder zeitliche Ausdehnung. Das Geoinformationssystem FirGIS bietet außerdem die Möglichkeit, bereits vorhandene wie auch zukünftige Information anderen Interessenten vor allem auch vor Ort zur Verfügung zu stellen.The mapping and analysis of landcover and landuse changes in a part of the Nigerian Chad Basin was the target of this thesis. In spite of a considerable general interest in Lake Chad, the biggest lake of West Africa, it is difficult to obtain topographical and thematic information about this region. Until today, many interrelations regarding the past and the future of the lake remain unclear. One reason for this is the comparatively poor data situation. Most of the maps and data, particularly landuse information, are not up-to-date. As far as data or maps of landcover and landuse were already available, they were structured and integrated into the regional geographic information system FirGIS. However, remote sensing data was used as main source for the evaluations. Image data gathered from airplanes or satellites provide the only extensively available multi-temporal up-to-date information of the research area. The analysis of the different remote sensing data was carried out by methods of digital image interpretation, on the one hand by visual interpretation and on the other hand - to a larger portion - by automatic digital procedures. The procedures in detail depended on the question and particularly on the data base structure. Current and historical aerial photographs were visually interpreted and then digitised using the vector data model. In most cases digital pre-processing, such as geographic rectification, contrast enhancement and mosaicing, were applied. Satellite scenes, however, were predominantly processed directly in digital form using the raster data model. In addition to the data preparation by digital image interpretation techniques the evaluations were carried out by means of digital classification. Further important steps of investigation that have been applied include different visualisation techniques of multi-temporal data, the computing of vegetation indices as well as different geoprocessing techniques for change detection. One main conclusion in respect to methodology particularly when using multi-temporal data is that automatic procedures by themselves do not provide satisfying results. Instead, semi-automatic evaluations, which include additional visual interpretations, considerably improved the quality of the results. In addition, such an approach favours the common evaluation of data of different remote sensing platforms, such as aerial photographs and satellite scenes, as well as the comparison of atmospherically non-corrected satellite scenes of different recording dates. The classification of all data was carried out using a common multi-level classification scheme, which was specifically adapted to the conditions in the Chad Basin. The results derived from the remote sensing data were for presentation purposes subdivided according to four dimensions of time. Attachment 1 Starting with a current detailed digital map of landcover and landuse, a 3500 km² subset of the Nigerian Chad Basin is presented. The map originates in aerial photographs of a scale of 1 : 25 000 and is enclosed in this thesis as a hardcopy. The main criterion regarding landcover is the distribution of the sediments: About 40% of the investigation area is covered by sandy sediments, the remaining larger part by clayey sediments. Few small expanses of water cover less than 1%. Built-up areas - predominantly settlements - also take up about 1% of the research area. They are mainly located on the sandy substratum. Agriculturally productive land occupies 53% of the total area and can be found both on the sandy and on the clayey areas. On the latter, both, traditional dry season cultivation (12%) as well as large area irrigation cultivation (22%) are practised. The sandy sediments are used for the traditional rainy season cultivation (18%). However, only one third of the rainy season land is currently under use, whereas the larger part is left as fallow. Further agricultural activity, such as rice cultivation, river irrigation and the cultivation following the seasonally receding Lake Chad (1% all together) is practised on both of the two substrata. Only little more than a quarter of the investigation area (27%) is covered by a mainly sparse tree cover. Though the sand areas show a clearly denser tree cover (41%) than the clay areas (14%). Besides the two-dimensional elements also linear elements such as roads, pathes, rivers, non-perennial rivers and channels were mapped in detail. Figure 45 Based on the current landuse map the dynamic seasonal behaviour of the various landcover and landuse units in an approximately 1100 km² central subset of the research area was examined. For this purpose five SPOT-XS satellite scenes of the vegetation period 1995/96 were consulted. As was expected, the most essential seasonally variable influences were the factors water and vegetation. In addition bush fires which are set at different times of the year, strongly influence the spectral response. As a summary for the phenological analyses of all different objects and their corresponding spectral behaviour at different times of the year, a detailed landcover and landuse classification of the season 1995/96 was developed. The presented results were obtained from a complex hierarchical satellite image classification with differentiated assignment rules. Compared to the map made from aerial photographs, the strength of the satellite image classification lies in the mapping of two-dimensional elements like sediments, farming areas and vegetation. For these object classes a higher differentiation due to the multi-spectral information contained in the different satellite scenes is possible and therefore better results in automatic processes are delivered. The comparison of the results obtained from the two examinations, however, revealed only restricted comparability due to the different data sources and the resulting divergent approach and data model used. Figure 6 With the experiences from the examination of the seasonal dynamics, in a further step, all satellite scenes available for the research area were evaluated in order to obtain knowledge about the inter-annual differences represented in the satellite scenes recorded at different times as well as about their causes. These evaluations concentrated on vegetation changes. As an ideal basis multi-temporal vegetation indices were employed for comparison and for derivation of change detection maps and precipitation data were consulted for the interpretation. Only in rare cases inter-annual differences could be looked at isolatedly. More often, inter-annual and seasonal alterations as well as long-term oscillations are combined in the satellite scenes. Nevertheless, a summarizing interpretation in form of a time series over 24 years derived from classified vegetation indices is presented. This time series can be subdivided in three periods: During the 1970s a weak general decrease in vegetation cover has to be recorded; there are no obvious differences between the low-rainfall period at the beginning of the decade and the period at the end of the decade with rainfall at or above average. These could be symptoms for anthropogenous causes for the vegetation reduction. A clear break is represented by the satellite scenes of the 1980s. They show extremely low vegetation cover at this very low-rainfall decade. The satellite scenes of the 1990s give the impression of recently more humid conditions, which however can only be verified for the end of the decade (without satellite cover), when precipitation conditions were increasing again. Figure 52Finally, the evaluations of historical aerial photographs of 1957 enabled the analysis of long-term developments in the investigation area. The results are presented in form of a historical map (enclosed as hardcopy in this thesis), as different change maps and quantitatively in form of diagrams. As far as land cover is concerned, expanses of open water decreased to a fifth of the area of 1957 in the current maps. A drastic fall was also observed for the vegetation cover (decrease of 37% within 33 years). In this case, primarily the vegetation cover with a high (by approximately 76%) and a medium density (by approximately 42%) was decimated. The area used by man has extended clearly. In 1957 an area of 70% of the investigation area was without anthropogenous use, whereas in 1990 it decreased to 31%. The settlement area has doubled in this period; taking into account the modern plants of the irrigation project, the area is even five times greater than in 1957. Unlike for the settlements, the area used for agriculture was not extended considerably, except for the large irrigation project. The currently used area for the traditional rainy season cultivation takes 6% of the total area at both times. Only the extent of the fallow land has been tripled. The dry season acreage has been reduced by a third. Instead, the extensive irrigation cultivation, which operated succesfully only during few years, has effectively gained area. Attachment 2An important result of this thesis is the integration of all used data and information on landcover and landuse in the Chad Basin including its neighbouring areas within the regional geographic information system FirGIS. The information system contains all base data as well as all results and additional information relating to the topics mentioned above. Therefore, a future continuation by thematic, spatial or temporal extension is easily possible. In addition, the geographic information system FirGIS offers the possibility to make already obtained data as well as information gathered in future available for all interested parties especially in the research area itself