3D Analyst

3D Analyst

Components• ArcScene

– Is where 3D Analyst is located– Visualization and Some Analysis

• ArcGlobe– Like Google Earth – google’s is better

• ArcMap - does NOT display 3D!• ArcCatalog – can preview in 3D

3D Data• Has a Z value• Elevation is most common Z value• But can also represent

– Pollution levels– Noise levels– Precipitation …. Etc.

Kinds of 3D data structures• DEM raster

• TIN (Triangulated Irregular Network)

TIN• Every 3

points of Z are connected to make a Triangle w/ Area, Slope, and Aspect.

3D view• Open ArcScene• Load DEM or TIN• Raster will be flat!• Set base height• Set vertical exaggeration • Illumination of DEM

Navigation tools different• General nav tool• Zoom tool Fly tool• Guess what?• Expand field of view• Narrow Field of View

Done while we go through these

demos

Vertical Exaggeration• Why?

– used to emphasize small changes– bring z-units into proportion with x,y

units• It is a only visual effect that does

NOT affect analysis

Illumination • Every Scene has a light source – the sun• Thus different parts of the scene are

illuminated differently• The sun’s position is described by…

– The sun’s azimuth is measured from 0 (north) to 360 (north) ccw. (315 (NW) is default)

– The sun’s altitude (0-90) is its height above the horizion.

Layer Properties• Base Heights

– establishes the elevations of surface locations and features.

• Extrusions – tells 3D Analyst how high a feature rises

above the ground or extends below it.

Base Heights• Elevation values that are used to display

a layer in 3D. • These values can come from various

places.– layer:

• the node elevations in a TIN, • the cell values in a raster, • the z-values in a 3D feature layer, •or the elevation attribute values for a 2D feature

layer.

Rendering• In layer’s properties• Scene Layer properties

Extrusions• three-dimensional extension of

features. – An extruded point a line;– an extruded line a wall; – an extruded polygon a chunk.

• There are many methods used to do this

Surface Calculations• Slope• Aspect• Hillshade• Contours• (Reclassification) • Pretty much the same as ArcGIS

but tools in 3D Analyst Tools

Adding 2D data• Turning on in TOC does not do

much – maybe can’t even see it!• Have to set the layer’s elevations

– Layer properties/Base Heights from DEM