GIS Concepts & Methods Visualization

1.  GIS Concepts & MethodsVisualization « 3D & Virtual Reality » Summary

2. Brief introduction • What is 3D visualization in GIS? • A real world simplification. • A combination of tools, GIS data & hardware focused on reproducing graphicalyelements from the landscape. • Interactive consulting & browsing interface. Girona City: Picture & 3D modalization ofered by Josep Caimel. StrateGISt Consulting S.L.

3. Moving from 2D to 3D • Moving from 2D to 3D is labor intense, requiring significant effort, time and cost.

4. Moving from 2D to 3D • But the benefits must be taken into acount. • 3D allows fly-overs showing the particular cases of study • Analyzing de data, the Z value can be an improving variable. • 3D visualizations become more realistic than flat maps. • Therefore they are a usefull tool to managers to quickly analyze the isues of interest such as hydrologic, aesthetic decisions, habitats, fire suppression and so on. • Creating 3D data depend of important technical skills. • But once reached, it is easy to exploit getting notable improvements.

5. Handicaps/dificulties of 3D GIS I • Hardware • 3D modelation and visualization cunsume high hardware resources • 3D data use to need huge space disck comparing within 2D • Screens devices must have high resolution • A powerfull video card should be installed into computers • Software • 3d data visualization will need new soft applications to manage the data • Applications not allways do all what we need. • Tecnical Skills • Technicians will need to learn new data structure and how to manage it. • Obviously a new software interface will apear at the screen

6. Data source / Data cration I • Data Origin • Planimetric/topographical maps • Hypsonometric lines / Altitude points • High of building lines (obtained by photogrammetric restitutions from calibrated images) • Data creation / Data capture • GPS, sounders • Topograpical works • Field work (naked eyes observation)

7. Airborne LIDAR SIR-C image. Isabela Island (Galápagos, Ecuador). April 1994 Data source / Data cration II • Data sources • 3D data products from companies (eg. ICC, USGS,…) • Other 3D data origens • Interferometry • Satelital Radar Images • Laser scanner: LIDAR (airborne lasers). «LIght Detection And Ranging»

8. Z Data usage I • How to deal with 3D row data? • 3D data must lock like 2D data. There is only one diferece: • 2D is composed by X and Y axis coordinates • 3D consist in 2D data plus a Z axis Y X

9. Elevation curves It’s Orthogonal view displaying colors by heigh displaying colors simulating sea depth Merging diferent results Data usage II • Example of 3D data usage

10. 3D to 3D view I • From 3D data to 3D visualization • If X and Y values represents latitude and longitude location, Z value is representing the altitude of each element. • To use Z, we have to derive a new cartography: • Obtaining new values (or cartography layers), like: • Interpolation of whole 3D coberture data (DEM, DTM)

11. 3D to 3D view II • Calculation of shadows (implementing azimut sun radiation) • Calculation of slope values (by trigonometry) • etc.

12. 3D Data types • Raster • DEM or DTM. (Digital Elevation Models or Digital Terrain Models) • Pixel elemental structure. • Most habitual used. • Easiest to produce. • Calculation results derive in new cartography coverture • Vectorial • TIN (Triangular Irregular Network) • Triangular vectors connecting key elevation points • Results do not need to derive into new cartographic coverture.

13. TIN data type structure • TIN example:

14. Displaing data • Interpolation Vs Extrude • Interpolation is used to create surfaces • Extrude create 3D elements (eg. Buildings)