Universidade Federal de Viçosa Departamento de Informática - DPI

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1 - DPI Sistema Interativo para Posicionamento de Observadores em Terrenos Representados por Modelos Digitais de Elevacao --- An Interactive System to Site Observer in Terrains represented by Digital Elevation Models Chaulio R. Ferreira Salles V. G. Magalhães Marcus V. A. Andrade

2 - DPI Introduction An important GIS application on terrains concerns visibility. For example, find the set of points on the terrain which are visible from some particular point (the observer).

3 - DPI Introduction These applications include telecommunications and military monitoring. For example, an observer may be a mobile phone tower or a monitoring tower.

4 - DPI Introduction These applications include telecommunications and military monitoring. For example, an observer may be a mobile phone tower or a monitoring tower.

5 - DPI Introduction These applications include telecommunications and military monitoring. For example, an observer may be a mobile phone tower or a monitoring tower.

6 - DPI Introduction An important problem related to visibility is siting observers in order to obtain an optimal visual coverage of a terrain. We will present an interactive system to solve this problem.

7 - DPI Terran visibility There are several ways to represent terrains in a computer. We will consider a terrain represented as a matrix storing elevation of regularly spaced terrain points.

8 - DPI Terran visibility An observer is a point (in the space) from which we wish to see or communicate with other points, called targets. The radius of interest, R, of O means the distance the observer can see. For example, for a observation tower, R is the maximum distance that a person on the tower can see;

9 Terran visibility - DPI T is visible from O if the distance between O and T is at most R and if there is no terrain point between O and T higher than OT (OT is called LOS line of sight); T 1 is visible T 2 is not

10 - DPI Terran visibility The viewshed, V, of O is the set of base points whose corresponding targets are visible from O. The visibility index, VIX, of O is the number of targets that are visible from O. Terrain visualization Viewshed

11 - DPI Terran visibility Given a set of observers: The joint viewshed is the union of the individual viewsheds in the set. The joint visibility index of a set of observers is the number of targets visible from at least one observer in the set. Terrain visualization Joint viewshed

12 - DPI Terran visibility We will deal with the following problem: find the minimum number of observers needed to cover a given percentage of a terrain. This is a NP-Hard problem. Some heuristics to solve this problem: Greedy GRASP Greedy + local search... }Previous work published in GeoInfo 2010: Heuristics to site observers in a terrain represented by a digital elevation matrix

13 - DPI Objective Develop an interactive system to help the observer siting process: Provide heuristics to automatically site observers. Provide tools to manually site observers or change a solution obtained by a heuristic. Simulate and compare different solutions obtained by manual siting or by the heuristics.

14 - DPI The proposed solution An interactive system developed in C++/QT.

15 - DPI The proposed solution Main functionalities: Add a new observer by clicking in the terrain. Remove an observer previously selected. Move an observer by dragging and dropping it. Change solution's parameters like observer's radius of interest or its elevation.

16 - DPI Terran visibility Main functionalities: Automatically site observers using one of three heuristics. After the automatic siting, it is possible to visualize the solution and manually modify it.

17 - DPI Terran visibility Movie

18 - DPI Conclusions and future works We have developed an interactive system to help the observer siting process. The user can interactively modify a solution and visualize it. The GUI can be used to help the decision taking process: for example, an user can visualize the impact of modifications in the solution (an observer remotion, the change in the observers' height, etc).

19 - DPI Conclusions and future works This is an ongoing work. Future works: Run tests to verify the advantages of the interactive system. Improve the usability. Integrate the system with a open source GIS. Develop new features. For example, allow the user to add layers to the map.

20 - DPI Thank you! Any questions or suggestions?