Displaying Surfaces chp 10

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Displaying raster surfaces?

Drawing rasters that represent continuous surface data with separate classes

Drawing rasters that represent continuous surface data with a continuous color ramp

Drawing thematic rasters that represent unique categories such as land cover

Stretching a raster to improve the visual contrast

Multiband raster color band assignments

Displaying TIN surfaces?

drawing TIN faces by:

elevation

aspect

slope

tag value

Drawing TIN nodes by elevation

Drawing TIN edges grouped with unique symbol

shape of a surface?

Slope

incline, or steepness, of a surface

Aspect

Direction a slope faces

Slope and Aspect in Raster and TINS

Raster: slope and aspect are calculated for each cell by fitting a plane to the z-values of each cell and its eight surrounding neighbors

TIN: each triangle face defines a plane with a slope and an aspect

Hillshades

The patterns of light and dark that a surface would show when illuminated from a particular angle

Contours

Lines that connect all contiguous locations with the same height (or other) value in the input grid or TIN

Calculating Slope?

Slope can be measured in degrees from horizontal (0-90) or percent slope, which is the rise divided by the run, times 100.

What is slope?

TIN: the maximum rate of change in elevation across each triangle

Raster: the maximum rate of change in elevation over each cell and its 8 neighbor

Calculating Aspect?

Counterclockwise in degrees

from 0 (due north) to 360

again due north, coming full circle

The value of each cell in an aspect grid indicates the direction in which the cell's slope faces.

Flat slopes have no direction and are given a value of -1.

Why map contours?

Identify which locations have the same value

(elevation, temperature, precipitation, pollution, or atmospheric pressure)

Gain general impression of the gradation of values

2 ways to create contours?

Click the surface with the Contour Tool

Create a single contour line which exist as 3D graphic

Use the Contour surface analysis command

Creates a series of contours with a given contour interval for the whole surface and are saved as feature class with height attribute

What is a line of sight?

A line between 2 points that shows the parts of the surface along the line that are visible to or hidden from an observer.

What is the viewshed?

It identifies the cells in an input raster that can be seen from one or more observation points or lines

Hillshade?

obtains the hypothetical illumination of a surface

Azimuth?

the angular direction of the sun

measured from north in clockwise degrees from 0 to 360

default is 315 (NW)

Altitude?

the slope or angle of the illumination source above the horizon

measured in degrees, from 0 (on the horizon) to 90 degrees (overhead)

default is 45 degrees.

Reclassifying data?

replacing input cell values with new output cell values

Why reclassify your data?

To replace values based on new information

To classify certain values together for display

To classify certain values together for conversion to vector format for analysis

To reclassify values to a common scale

To set specific values to nodata or to set nodata cells to a value

Converting surfaces to vector data?

Converting rasters to features

Convert raster to categorical data

Convert categories to polygons

Use polygons with other vector data and select areas that meet the criteria

Convert TINs to features

Extract slope and aspects polygons directly from TIN

Extract elevation values of nodes in TIN as point feature class

Creating 3D features?

Deriving existing features height from a surface

Deriving existing features height using an attribute

Creating 3D features by digitizing over a surface

Creating 3D graphics by digitizing over a surface

Creating a new scene?

Adding data in ArcScene

Adding data from ArcCatalog

drag and drop onto the scene

Adding data from ArcMap

Adding 3D graphics to a scene?

Copying and pasting 3D graphics from ArcMap

Feature data and 3D?

Feature geometries

point, line, or polygon

Z-values

values that refer to the elevation or height of the features

Draping features

use values in surface model as z-values for features

Extruding features

extrude using an attribute e.g. building height or number of stories

Defining the z-values for a layer?

Setting the base height from an attribute

Setting a feature layer’s base heights using a surface

Extruding the features in a layer

Raster data and 3D?

Defining the 3D properties of a raster layer

Converting z-units to x,y units

Offsetting the heights in a layer

Controlling when a layer is rendered

Managing scene viewers?

Adding a viewer

Closing a viewer

Managing viewers

Changing the viewer settings?

Setting a viewer to 2D

Changing the roll and pitch of a viewer

Specifying the coordinates of the observer or target

Setting the properties of a scene?

Changing the vertical exaggeration

Using animated rotation

Changing the background color

Changing the scene illumination

Changing the scene extent

Changing the scene coordinate system

Identifying and selecting features?

Selecting features interactively by clicking in a scene

Selecting features interactively by clicking on a table

Selecting features by their attributes

Selecting features by their location

Exporting a scene?

Exporting a 2D graphic of a scene

Exporting a 3D VRML model of a scene