The potential impacts of sea level rise (SLR) on 95% of the land areas of the Florida Keys were e... more The potential impacts of sea level rise (SLR) on 95% of the land areas of the Florida Keys were estimated through analysis of a digital elevation model (DEM) derived from airborne light detection and ranging (LiDAR) measurements in a geographic information system. The topographic detail of the LiDAR DEM allowed projections of land, population, and property inundation in 0.15 m increments across a broad range of SLR scenarios for the next century. The results showed that a 0.6 m SLR by 2100 would inundate about 70% of the total land surface, but smaller percentages of the population (17%) and real property (12%). A 1.5 m rise in sea level during the same period would inundate 91% of the land surface, 71% of the population and 68% of property in the study area. Comparison of inundation dynamics indicates that the Lower Florida Keys are more susceptible to SLR than the Upper Florida Keys. The inundation dynamics exhibit non-linear behavior and demonstrate tipping points in inundation processes beyond which the inundation of land, population, and property speeds up. Acceleration of SLR will amplify the non-linear inundation, causing tipping points to be reached sooner.
Nutrient loading and eutrophication in coastal waters are the causes of water quality degradation... more Nutrient loading and eutrophication in coastal waters are the causes of water quality degradation and loss of marine biota, which has led to ecological imbalance. Understanding and modeling the level of eutrophication as a function of environmental parameters can be beneficial to coastal ecosystem management. The limitation of deterministic and empirical models in accurately predicting the level of algal blooms, and the nonlinear relationship between the water quality and environmental parameters and that of the level of chlorophyll a necessitate a new approach using machine learning and data-driven modeling. A multilayer perceptron-back propagation (MLP-BP) algorithm of artificial neural network (ANN) was used to predict the level of eutrophication (chlorophyll a) from water quality parameters monitored at two Florida Bay water quality monitoring stations (FLAB03 and FLAB14). Based on the correlation of monthly nutrients (total phosphate, nitrite, ammonium) and other water data (temperature, turbidity, and dissolved oxygen) to the level of chlorophyll a, an input-output data structure was selected. Seven input data scenarios were studied, and model performance was compared using four indices. Monthly data from 1992 to 2004 were partitioned into training and testing subsets. Results show that chlorophyll a was predicted well with the selected inputs, with an average R 2 and model efficiency (E) of 0.856 and 0.582, respectively. Prediction with antecedent chlorophyll a alone gave a stable result with smaller error and higher performance attributed to easier and more efficient training. It was also found that ANN performed better at FLA03 than at FLA14. It is shown that the MLP-BP technique is applicable to the monitoring and prediction of algal blooms and will be crucial to coastal watershed management.
This paper presents a 3D traffic animation system that provides features of vehicle interaction a... more This paper presents a 3D traffic animation system that provides features of vehicle interaction and storm surge response to emulate realistic scenarios in a hurricane affected area. The proposed system constructs road objects based on a series of line segments. Vehicles on the roads are animated by keeping them coherent with the direction of the road segment and adjusting their speeds with respect to one another. The vehicle speed is controlled based upon a collision-circumventing policy and they automatically respond to flood water caused by a storm surge. The system can automatically plant lamp posts along the roads, which also respond to surge flooding. An implementation conducted with the 3D scenes on a couple of south Florida's surge-susceptible areas demonstrates the system's excellence in animating real traffic scenes and impacts of storm surge on coastal regions.
We present a damage pattern mining framework for hurricane data on residential houses using aeria... more We present a damage pattern mining framework for hurricane data on residential houses using aerial photographs with 1:3000 based scale. The vertical photographs are normally collected for an overview of a disaster area or for more detailed assessment. Damage on roof, especially for shingles torn off, is expected to be discovered in a more efficient and automatic way instead of going through the high-resolution aerial photograph for numerous details. The discovered damage patterns can then be used for hurricane damage assessment and impacts on different geographical areas. Our methodology is: (1) applying a novel and effective segmentation method on each residential house on the aerial photograph of one community, (2) using the segmentation results to obtain a set of indexing parameters for each house representing the damage level of roof cladding as well as the patterns of damage, (3) using these parameters to select several templates representing the damage patterns so that users can issue queryby-example (QBE) queries. The proposed segmentation method is an unsupervised simultaneous partition and class parameter estimation algorithm that considers the problem of segmentation as a joint estimation of the partition and class parameter variables. By utilizing this segmentation method, the indexing parameters can be obtained automatically. The QBE capability can assist in finding similar damage patterns on the roof of the residential houses in different locations in the image databases. Experiments based on the aerial photographs of Hurricane Andrew in 1992 are conducted and analyzed to show the effectiveness of the proposed Hurricane damage pattern mining framework.
Energy-minimizing active contour models (snakes) have been proposed for solving many computer vis... more Energy-minimizing active contour models (snakes) have been proposed for solving many computer vision problems such as object segmentation, surface reconstruction, and object tracking. Dynamic programming which allows natural enforcement of constraints is an effective method for computing the global minima of energy functions. However, this method is only limited to snake problems with one dimensional (ID) topology (i.e., a contour) and cannot handle problems with two-dimensional (2D) topology. In this paper, we have extended the dynamic programming method to address the snake problems with 2D topology using a novel graph reduction algorithm. Given a 2D snake with first order energy terms, a set of reduction operations are defined and used to simplify the graph of the 2D snake into one single vertex while retaining the minimal energy of the snake. The proposed algorithm has a polynomial-time complexity bound and the optimality of the solution for a reducible 2D snake is guaranteed. However, not all types of 2D snakes can be reduced into one single vertex using the proposed algorithm. The reduction of general planar snakes is an NP-complete problem. The proposed method has been applied to optimize 2D building topology extracted from airborne LIDAR data to examine the effectiveness of the algorithm. The results demonstrate that the proposed approach successfully found the global optima for over 98% of building topology in a polynomial time.
This paper illustrates branch breaking and flying effect animation for trees in our 3D interactiv... more This paper illustrates branch breaking and flying effect animation for trees in our 3D interactive visualization system for hurricanes and storm surge flooding. The tree branch breaking and flying effect animation extends our current tree animation framework by estimating the destination quadrant, direction (angle) and traveling speed with which a branch breaks and flies across the terrain. These calculations thus assist in simulating the potential threats to property and human lives posed by the flying branches during a hurricane, and add to the realism and appeal of our system. We utilize 3D tree models created with 3DSmax and implement the animation effects via OpenGL and nVidia CG shader language.
H urricanes are the most devastating natural hazard affecting the populated US East and Gulf coas... more H urricanes are the most devastating natural hazard affecting the populated US East and Gulf coasts. One of the major threats associated with hurricanes is storm surge. The storm surge can damage buildings and infrastructure, block escape routes, and drown people by flooding low-lying coastal areas. More than 8,000 people were killed largely from storm-surge flooding when a hurricane made landfall at Galveston, Texas, in 1900. The death toll in the US from storm-surge hazards has declined drastically over the last several decades because of a low hurricane activity and implementation of timely evacuation from storm-surge zones. The evacuation zones are determined through a combination of near-shore elevations and storm surge predicted by the numerical model Sea, Lake, Overland Surges from Hurricanes (Slosh) 1 developed by the National Oceanic and Atmospheric Administration (NOAA). As coastal populations grow and decades of increased hurricane activity occur, 2 the risk of drowning thousands of people living in low-lying areas, such as South Florida and New Orleans, Louisiana, increases as demonstrated by Hurricanes Katrina and Rita in 2005. Several hundred people were killed along the Mississippi coast by the storm-surge flooding induced by Katrina.
This paper describes an implementation of vertex weighting for real-time animation of 3D trees as... more This paper describes an implementation of vertex weighting for real-time animation of 3D trees as a result of wind force and direction. This method improves over similar techniques because it incorporates individual branch animation on 3D models, whereas previous works perform animations on the model as a whole or use planar billboards to visualize the tree. Our tree animation is used in an interactive system that visualizes the effects caused by a hurricane's impact on a virtual city. The system uses models created with 3D Studio Max and the animations are implemented in OpenGL and the nVidia Cg shader language.
ROBERTSON, W.; WHITMAN, D.; ZHANG, K., and LEATHERMAN, S.P., 2004. Mapping shoreline position usi... more ROBERTSON, W.; WHITMAN, D.; ZHANG, K., and LEATHERMAN, S.P., 2004. Mapping shoreline position using airborne laser altimetry. Journal of Coastal Research, 20(3), 884-892. West Palm Beach (Florida), ISSN 0749-0208.
IEEE Transactions on Geoscience and Remote Sensing, 2006
This paper presents a framework that applies a series of algorithms to automatically extract buil... more This paper presents a framework that applies a series of algorithms to automatically extract building footprints from airborne LIDAR measurements. In the proposed framework, the ground and non-ground LIDAR measurements are first separated using a progressive morphological filter. Then, building measurements are identified from non-ground measurements using a region growing algorithm based on the planefitting technique. Finally, raw footprints for segmented building measurements are derived by connecting boundary points, and the raw footprints are further simplified and adjusted to remove noise caused by irregularly spaced LIDAR measurements. Data sets from urbanized areas including large institutional, commercial, and small residential buildings were employed to test the proposed framework. Quantitative analysis showed that the total of omission and commission errors for extracted footprints for both institutional and residential areas was about 12%. The results demonstrated that the proposed framework identified building footprints well.
This paper describes an approach to develop a high performance animation environment for storm su... more This paper describes an approach to develop a high performance animation environment for storm surge. The system provides the capability to simulate the storm surge effects in the physical world by (1) modeling a region using the airborne light Detection And Ranging (LIDAR) data, USGS orthophotos, RLG road data and photos; (2) animating the storm impact by using the features of this model; and (3) providing the capability for users to explore the animation environment. We present our system by modeling the dataset collected from Ft. Lauderdale, a region in South Florida, USA.
IEEE Transactions on Geoscience and Remote Sensing, 2003
Recent advances in airborne light detection and ranging (LIDAR) technology allow rapid and inexpe... more Recent advances in airborne light detection and ranging (LIDAR) technology allow rapid and inexpensive measurements of topography over large areas. This technology is becoming a primary method for generating high-resolution digital terrain models (DTMs) that are essential to numerous applications such as flood modeling and landslide prediction. Airborne LIDAR systems usually return a three-dimensional cloud of point measurements from reflective objects scanned by the laser beneath the flight path. In order to generate a DTM, measurements from nonground features such as buildings, vehicles, and vegetation have to be classified and removed. In this paper, a progressive morphological filter was developed to detect nonground LIDAR measurements. By gradually increasing the window size of the filter and using elevation difference thresholds, the measurements of vehicles, vegetation, and buildings are removed, while ground data are preserved. Datasets from mountainous and flat urbanized areas were selected to test the progressive morphological filter. The results show that the filter can remove most of the nonground points effectively.
The potential impacts of sea level rise (SLR) on 95% of the land areas of the Florida Keys were e... more The potential impacts of sea level rise (SLR) on 95% of the land areas of the Florida Keys were estimated through analysis of a digital elevation model (DEM) derived from airborne light detection and ranging (LiDAR) measurements in a geographic information system. The topographic detail of the LiDAR DEM allowed projections of land, population, and property inundation in 0.15 m increments across a broad range of SLR scenarios for the next century. The results showed that a 0.6 m SLR by 2100 would inundate about 70% of the total land surface, but smaller percentages of the population (17%) and real property (12%). A 1.5 m rise in sea level during the same period would inundate 91% of the land surface, 71% of the population and 68% of property in the study area. Comparison of inundation dynamics indicates that the Lower Florida Keys are more susceptible to SLR than the Upper Florida Keys. The inundation dynamics exhibit non-linear behavior and demonstrate tipping points in inundation processes beyond which the inundation of land, population, and property speeds up. Acceleration of SLR will amplify the non-linear inundation, causing tipping points to be reached sooner.
Nutrient loading and eutrophication in coastal waters are the causes of water quality degradation... more Nutrient loading and eutrophication in coastal waters are the causes of water quality degradation and loss of marine biota, which has led to ecological imbalance. Understanding and modeling the level of eutrophication as a function of environmental parameters can be beneficial to coastal ecosystem management. The limitation of deterministic and empirical models in accurately predicting the level of algal blooms, and the nonlinear relationship between the water quality and environmental parameters and that of the level of chlorophyll a necessitate a new approach using machine learning and data-driven modeling. A multilayer perceptron-back propagation (MLP-BP) algorithm of artificial neural network (ANN) was used to predict the level of eutrophication (chlorophyll a) from water quality parameters monitored at two Florida Bay water quality monitoring stations (FLAB03 and FLAB14). Based on the correlation of monthly nutrients (total phosphate, nitrite, ammonium) and other water data (temperature, turbidity, and dissolved oxygen) to the level of chlorophyll a, an input-output data structure was selected. Seven input data scenarios were studied, and model performance was compared using four indices. Monthly data from 1992 to 2004 were partitioned into training and testing subsets. Results show that chlorophyll a was predicted well with the selected inputs, with an average R 2 and model efficiency (E) of 0.856 and 0.582, respectively. Prediction with antecedent chlorophyll a alone gave a stable result with smaller error and higher performance attributed to easier and more efficient training. It was also found that ANN performed better at FLA03 than at FLA14. It is shown that the MLP-BP technique is applicable to the monitoring and prediction of algal blooms and will be crucial to coastal watershed management.
This paper presents a 3D traffic animation system that provides features of vehicle interaction a... more This paper presents a 3D traffic animation system that provides features of vehicle interaction and storm surge response to emulate realistic scenarios in a hurricane affected area. The proposed system constructs road objects based on a series of line segments. Vehicles on the roads are animated by keeping them coherent with the direction of the road segment and adjusting their speeds with respect to one another. The vehicle speed is controlled based upon a collision-circumventing policy and they automatically respond to flood water caused by a storm surge. The system can automatically plant lamp posts along the roads, which also respond to surge flooding. An implementation conducted with the 3D scenes on a couple of south Florida's surge-susceptible areas demonstrates the system's excellence in animating real traffic scenes and impacts of storm surge on coastal regions.
We present a damage pattern mining framework for hurricane data on residential houses using aeria... more We present a damage pattern mining framework for hurricane data on residential houses using aerial photographs with 1:3000 based scale. The vertical photographs are normally collected for an overview of a disaster area or for more detailed assessment. Damage on roof, especially for shingles torn off, is expected to be discovered in a more efficient and automatic way instead of going through the high-resolution aerial photograph for numerous details. The discovered damage patterns can then be used for hurricane damage assessment and impacts on different geographical areas. Our methodology is: (1) applying a novel and effective segmentation method on each residential house on the aerial photograph of one community, (2) using the segmentation results to obtain a set of indexing parameters for each house representing the damage level of roof cladding as well as the patterns of damage, (3) using these parameters to select several templates representing the damage patterns so that users can issue queryby-example (QBE) queries. The proposed segmentation method is an unsupervised simultaneous partition and class parameter estimation algorithm that considers the problem of segmentation as a joint estimation of the partition and class parameter variables. By utilizing this segmentation method, the indexing parameters can be obtained automatically. The QBE capability can assist in finding similar damage patterns on the roof of the residential houses in different locations in the image databases. Experiments based on the aerial photographs of Hurricane Andrew in 1992 are conducted and analyzed to show the effectiveness of the proposed Hurricane damage pattern mining framework.
Energy-minimizing active contour models (snakes) have been proposed for solving many computer vis... more Energy-minimizing active contour models (snakes) have been proposed for solving many computer vision problems such as object segmentation, surface reconstruction, and object tracking. Dynamic programming which allows natural enforcement of constraints is an effective method for computing the global minima of energy functions. However, this method is only limited to snake problems with one dimensional (ID) topology (i.e., a contour) and cannot handle problems with two-dimensional (2D) topology. In this paper, we have extended the dynamic programming method to address the snake problems with 2D topology using a novel graph reduction algorithm. Given a 2D snake with first order energy terms, a set of reduction operations are defined and used to simplify the graph of the 2D snake into one single vertex while retaining the minimal energy of the snake. The proposed algorithm has a polynomial-time complexity bound and the optimality of the solution for a reducible 2D snake is guaranteed. However, not all types of 2D snakes can be reduced into one single vertex using the proposed algorithm. The reduction of general planar snakes is an NP-complete problem. The proposed method has been applied to optimize 2D building topology extracted from airborne LIDAR data to examine the effectiveness of the algorithm. The results demonstrate that the proposed approach successfully found the global optima for over 98% of building topology in a polynomial time.
This paper illustrates branch breaking and flying effect animation for trees in our 3D interactiv... more This paper illustrates branch breaking and flying effect animation for trees in our 3D interactive visualization system for hurricanes and storm surge flooding. The tree branch breaking and flying effect animation extends our current tree animation framework by estimating the destination quadrant, direction (angle) and traveling speed with which a branch breaks and flies across the terrain. These calculations thus assist in simulating the potential threats to property and human lives posed by the flying branches during a hurricane, and add to the realism and appeal of our system. We utilize 3D tree models created with 3DSmax and implement the animation effects via OpenGL and nVidia CG shader language.
H urricanes are the most devastating natural hazard affecting the populated US East and Gulf coas... more H urricanes are the most devastating natural hazard affecting the populated US East and Gulf coasts. One of the major threats associated with hurricanes is storm surge. The storm surge can damage buildings and infrastructure, block escape routes, and drown people by flooding low-lying coastal areas. More than 8,000 people were killed largely from storm-surge flooding when a hurricane made landfall at Galveston, Texas, in 1900. The death toll in the US from storm-surge hazards has declined drastically over the last several decades because of a low hurricane activity and implementation of timely evacuation from storm-surge zones. The evacuation zones are determined through a combination of near-shore elevations and storm surge predicted by the numerical model Sea, Lake, Overland Surges from Hurricanes (Slosh) 1 developed by the National Oceanic and Atmospheric Administration (NOAA). As coastal populations grow and decades of increased hurricane activity occur, 2 the risk of drowning thousands of people living in low-lying areas, such as South Florida and New Orleans, Louisiana, increases as demonstrated by Hurricanes Katrina and Rita in 2005. Several hundred people were killed along the Mississippi coast by the storm-surge flooding induced by Katrina.
This paper describes an implementation of vertex weighting for real-time animation of 3D trees as... more This paper describes an implementation of vertex weighting for real-time animation of 3D trees as a result of wind force and direction. This method improves over similar techniques because it incorporates individual branch animation on 3D models, whereas previous works perform animations on the model as a whole or use planar billboards to visualize the tree. Our tree animation is used in an interactive system that visualizes the effects caused by a hurricane's impact on a virtual city. The system uses models created with 3D Studio Max and the animations are implemented in OpenGL and the nVidia Cg shader language.
ROBERTSON, W.; WHITMAN, D.; ZHANG, K., and LEATHERMAN, S.P., 2004. Mapping shoreline position usi... more ROBERTSON, W.; WHITMAN, D.; ZHANG, K., and LEATHERMAN, S.P., 2004. Mapping shoreline position using airborne laser altimetry. Journal of Coastal Research, 20(3), 884-892. West Palm Beach (Florida), ISSN 0749-0208.
IEEE Transactions on Geoscience and Remote Sensing, 2006
This paper presents a framework that applies a series of algorithms to automatically extract buil... more This paper presents a framework that applies a series of algorithms to automatically extract building footprints from airborne LIDAR measurements. In the proposed framework, the ground and non-ground LIDAR measurements are first separated using a progressive morphological filter. Then, building measurements are identified from non-ground measurements using a region growing algorithm based on the planefitting technique. Finally, raw footprints for segmented building measurements are derived by connecting boundary points, and the raw footprints are further simplified and adjusted to remove noise caused by irregularly spaced LIDAR measurements. Data sets from urbanized areas including large institutional, commercial, and small residential buildings were employed to test the proposed framework. Quantitative analysis showed that the total of omission and commission errors for extracted footprints for both institutional and residential areas was about 12%. The results demonstrated that the proposed framework identified building footprints well.
This paper describes an approach to develop a high performance animation environment for storm su... more This paper describes an approach to develop a high performance animation environment for storm surge. The system provides the capability to simulate the storm surge effects in the physical world by (1) modeling a region using the airborne light Detection And Ranging (LIDAR) data, USGS orthophotos, RLG road data and photos; (2) animating the storm impact by using the features of this model; and (3) providing the capability for users to explore the animation environment. We present our system by modeling the dataset collected from Ft. Lauderdale, a region in South Florida, USA.
IEEE Transactions on Geoscience and Remote Sensing, 2003
Recent advances in airborne light detection and ranging (LIDAR) technology allow rapid and inexpe... more Recent advances in airborne light detection and ranging (LIDAR) technology allow rapid and inexpensive measurements of topography over large areas. This technology is becoming a primary method for generating high-resolution digital terrain models (DTMs) that are essential to numerous applications such as flood modeling and landslide prediction. Airborne LIDAR systems usually return a three-dimensional cloud of point measurements from reflective objects scanned by the laser beneath the flight path. In order to generate a DTM, measurements from nonground features such as buildings, vehicles, and vegetation have to be classified and removed. In this paper, a progressive morphological filter was developed to detect nonground LIDAR measurements. By gradually increasing the window size of the filter and using elevation difference thresholds, the measurements of vehicles, vegetation, and buildings are removed, while ground data are preserved. Datasets from mountainous and flat urbanized areas were selected to test the progressive morphological filter. The results show that the filter can remove most of the nonground points effectively.
Uploads
Papers by Keqi Zhang