Photorealistic three-dimensional(3-D)models are important tools for urban and disaster management planning because they contain useful visual and spatial information for assessing the situation and responding accordin...Photorealistic three-dimensional(3-D)models are important tools for urban and disaster management planning because they contain useful visual and spatial information for assessing the situation and responding accordingly.Thus,it is crucial for 3-D city models to maintain a high level of accuracy in portraying 3-D geometric objects.Despite that,significant research with respect to 3-D city models has been conducted;however,it is still difficult to create accurate 3-D representations,particularly across a wide area.Thus,this research is aimed at developing an automated 3-D city modeling application that utilizes a combination of aerial photographs,terrestrial light detection and ranging,and total station techniques for particularly dense urban areas.To enable the development of an automated 3-D city model,this research developed application software programmed in C++.This application enables users to generate 3-D images of buildings.Specifically,the 3-D city models are generated using the aerial photographs.The positional accuracy of the model is highly improved by comparing building models produced using a photogrammetric plotting instrument.Once created using a combination of aerial photos and terrestrial instruments,the 3-D city model is quantitatively assessed for completeness and suitability for commercial or public use.展开更多
Approximately 34,000 aerial photographs covering large parts of Ethiopia and dating back to 1935–1941 have been recently recovered.These allow investigating environmental dynamics for a past period that until now is ...Approximately 34,000 aerial photographs covering large parts of Ethiopia and dating back to 1935–1941 have been recently recovered.These allow investigating environmental dynamics for a past period that until now is only accessible from terrestrial photographs or narratives.As the archive consists of both oblique and vertical aerial photographs that cover rather small areas,methods of image-based modelling were used to orthorectify the images.In this study,9 vertical and 18 low oblique aerial photographs were processed as an ortho-mosaic,covering an area of 25 km2,west of Wukro town in northern Ethiopia.Using 15 control points(derived from Google Earth),a Root Means Square Error of 28.5 m in X 35.4 m in Y were achieved.These values can be viewed as optimal,given the relatively low resolution and poor quality of the imagery,the lack of metadata,the geometric quality of the Google Earth imagery and the recording characteristics.Land use remained largely similar since 1936,with large parts of the land being used as cropland or extensive grazing areas.Most remarkable changes are the strong expansion of the settlements as well as land management improvements.In a larger effort,ortho-mosaics covering large parts of Ethiopia in 1935–1941 will be produced.展开更多
文摘Photorealistic three-dimensional(3-D)models are important tools for urban and disaster management planning because they contain useful visual and spatial information for assessing the situation and responding accordingly.Thus,it is crucial for 3-D city models to maintain a high level of accuracy in portraying 3-D geometric objects.Despite that,significant research with respect to 3-D city models has been conducted;however,it is still difficult to create accurate 3-D representations,particularly across a wide area.Thus,this research is aimed at developing an automated 3-D city modeling application that utilizes a combination of aerial photographs,terrestrial light detection and ranging,and total station techniques for particularly dense urban areas.To enable the development of an automated 3-D city model,this research developed application software programmed in C++.This application enables users to generate 3-D images of buildings.Specifically,the 3-D city models are generated using the aerial photographs.The positional accuracy of the model is highly improved by comparing building models produced using a photogrammetric plotting instrument.Once created using a combination of aerial photos and terrestrial instruments,the 3-D city model is quantitatively assessed for completeness and suitability for commercial or public use.
文摘Approximately 34,000 aerial photographs covering large parts of Ethiopia and dating back to 1935–1941 have been recently recovered.These allow investigating environmental dynamics for a past period that until now is only accessible from terrestrial photographs or narratives.As the archive consists of both oblique and vertical aerial photographs that cover rather small areas,methods of image-based modelling were used to orthorectify the images.In this study,9 vertical and 18 low oblique aerial photographs were processed as an ortho-mosaic,covering an area of 25 km2,west of Wukro town in northern Ethiopia.Using 15 control points(derived from Google Earth),a Root Means Square Error of 28.5 m in X 35.4 m in Y were achieved.These values can be viewed as optimal,given the relatively low resolution and poor quality of the imagery,the lack of metadata,the geometric quality of the Google Earth imagery and the recording characteristics.Land use remained largely similar since 1936,with large parts of the land being used as cropland or extensive grazing areas.Most remarkable changes are the strong expansion of the settlements as well as land management improvements.In a larger effort,ortho-mosaics covering large parts of Ethiopia in 1935–1941 will be produced.
