This paper presents novel and effective methods for teaching about topography--or shape of terrain--and assessing 3-dimensional spatial learning using tangibles. We used Tangible Landscape--a tangible interface for geospatial modeling--to teach multiple hands-on tangible lessons on the concepts of grading (i.e., earthwork), geomorphology, and hydrology. We examined students' ratings of the system's usability and user experience and tested students' acquisition and transfer of knowledge. Our results suggest the physicality of the objects enabled the participants to effectively interact with the system and each other, positively impacting ratings of usability and task-specific knowledge building. These findings can potentially advance the design and implementation of tangible teaching methods for the topics of geography, design, architecture, and engineering.

Tangible Landscape is a tangible interface for geographic information systems (GIS). It interactively couples physical and digital models of a landscape so that users can intuitively explore, model, and analyze geospatial data in a collaborative environment. Conceptually Tangible Landscape lets users hold a GIS in their hands so that they can feel the shape of the topography, naturally sculpt new landforms, and interact with simulations like water flow. Since it only affords a bird's-eye view of the landscape, we coupled it with an immersive virtual environment so that users can virtually walk around the modeled landscape and visualize it at a human-scale. Now as users shape topography, draw trees, define viewpoints, or route a walkthrough, they can see the results on the projection-augmented model, rendered on a display, or rendered on a head-mounted display. In this paper we present the Tangible Landscape Immersive Extension, describe its physical setup and software architecture, and demonstrate its features with a case study.

Terrestrial laser scanning (TLS) is utilized to monitor bank erosion along a stream that has incised through historic millpond (legacy) sediment. A processing workflow is developed to generate digital terrain models (DTMs) of the bank's surface from the TLS point cloud data. Differencing of the DTMs reveals that the majority of sediment loss stems from the legacy sediment layer. The DTM time series is stacked into a voxel model to form a space-time cube (STC). The STC provides a compact representation of the bank's spatiotemporal evolution captured by the TLS scans. The continuous STC extends this approach by generating a voxel model with equal temporal resolution directly from the point cloud data. Novel visualizations are extracted from the STCs to explore patterns in surface evolution. Results show that erosion is highly variable in space and time, with large-scale erosion being episodic due to bank failure within legacy sediment.

We present TanGeoMS, a tangible geospatial modeling visualization system that couples a laser scanner, projector, and a flexible physical three-dimensional model with a standard geospatial information system (GIS) to create a tangible user interface for terrain data. TanGeoMS projects an image of real-world data onto a physical terrain model. Users can alter the topography of the model by modifying the clay surface or placing additional objects on the surface. The modified model is captured by an overhead laser scanner then imported into a GIS for analysis and simulation of real-world processes. The results are projected back onto the surface of the model providing feedback on the impact of the modifications on terrain parameters and simulated processes. Interaction with a physical model is highly intuitive, allowing users to base initial design decisions on geospatial data, test the impact of these decisions in GIS simulations, and use the feedback to improve their design. We demonstrate the system on three applications: investigating runoff management within a watershed, assessing the impact of storm surge on barrier islands, and exploring landscape rehabilitation in military training areas.

We consider the problem of extracting a river network and a watershed hierarchy from a terrain given as a set of irregularly spaced points. We describe TERRASTREAM, a "pipelined" solution that consists of four main stages: construction of a digital elevation model (DEM), hydrological conditioning, extraction of river networks, and construction of a watershed hierarchy. Our approach has several advantages over existing methods. First, we design and implement the pipeline so that each stage is scalable to massive data sets; a single non-scalable stage would create a bottleneck and limit overall scalability. Second, we develop the algorithms in a general framework so that they work for both TIN and grid DEMs. Furthermore, TERRASTREAM is flexible and allows users to choose from various models and parameters, yet our pipeline is designed to reduce (or eliminate) the need for manual intervention between stages.

Application of a spline approximation method to computation and analysis of lidar-based digital elevation models is investigated to determine its accuracy and capability to create surfaces at different levels of detail. Quadtree segmentation that adapts to the spatial heterogeneity of data points makes the method feasible for large datasets. The results demonstrate the importance of smoothing for the surface accuracy and noise reduction. A tension parameter is effective for tuning the level of detail in the elevation surface. Simultaneous computation of topographic parameters is applied to extraction of sand dunes' features for assessment of dune migration and beach erosion.

(1997). Reply to Comment by Desmet and Govers. International Journal of Geographical Information Science: Vol. 11, No. 6, pp. 611-618.

Modelling of erosion and deposition in complex terrain within a geographical information system (GIS) requires a high resolution digital elevation model (DEM), reliable estimation of topographic parameters, and formulation of erosion models adequate for digital representation of spatially distributed parameters. Regularized spline with tension was integrated within a GIS for computation of DEMs and topographic parameters from digitized contours or other point elevation data. For construction of flow lines and computation of upslope contributing areas an algorithm based on vector-grid approach was developed. The spatial distribution of areas with topographic potential for erosion or deposition was then modelled using the approach based on the unit stream power and directional derivatives of surface representing the sediment transport capacity. The methods presented are illustrated on study areas in central Illinois and the Yakima Ridge, Washington.

The concept of GRASS (Geographic Resources Analysis Support System) as an open system has created a favourable environment for integration of process based modelling and GIS. To support this integration a new generation of tools is being developed in the following areas: (a) interpolation from multidimensional scattered point data, (b) analysis of surfaces and hypersurfaces, (c) modelling of spatial processes and, (d) 3D dynamic visualization. Examples of two applications are given-spatial and temporal modelling of erosion and deposition, and multivariate interpolation and visualization of nitrogen concentrations in the Chesapeake Bay.