11) Surface Creation and Analysis

Question 1

________ represents phenomena that have values at every point across their extent

Answer 1

Surfaces

Question 2

________ can be represented using contour lines or isolines, arrays of points, TINs and rasters.

Answer 2

Surfaces

Question 3

Sets of lines of equal value across a surface and are frequently created to represent surfaces on a map.

Answer 3

Contours

Question 4

Can be regularly or irregularly distributed across a surface, usually used as inputs to interpolation, kriging, or triangulation tools to create raster or TIN surfaces.

Answer 4

Points

Question 5

Nets of triangular facets defined by nodes and edges that cover a surface.

Answer 5

Triangular Irregular Networks (TINs)

Question 6

Rectangular arrays of cells (or pixels), each of which stores a value for the part of the surface it covers.

Answer 6

Rasters

Question 7

Tools used to create continuous surface from discrete samples
with measured values, such as elevation or chemical concentration.

Answer 7

Interpolation Tools

Question 8

Interpolation Tools

Answer 8

1. Inverse Distance Weighted (IDW)
2. Natural Neighbor
3. Spline
4. Trend
5. Density
6. Topo To Raster
7. Creating TIN Surfaces
8. Kriging

Question 9

This determines cell values using a linearly weighted combination of a set of sample points.

Answer 9

Inverse Distance Weighted (IDW)

Question 10

This is similar to IDW except that the data points used to interpolate surface values for each cell are identified and
weighted using a Delauney triangulation, as in a TIN.

Answer 10

Natural Neighbor

Question 11

This estimates values using a mathematical function that minimizes
overall surface curvature or sharp bending, resulting in a smooth surface that passes exactly through the input points.

Answer 11

Spline

Question 12

This uses a global polynomial interpolation that fits a smooth surface defined by a mathematical function (a polynomial) to the input sample points.

Answer 12

Trend

Question 13

This produces a surface that represents how much or how many of some thing there are per unit area.

Answer 13

Density

Question 14

This is a specialized tool for creating hydrologically correct raster surfaces from vector data of terrain components such as elevation points, contour lines, stream lines, lake polygons, sink points, and study area polygons.

Answer 14

Topo To Raster

Question 15

Can be generated from either surface source measurements or by converting another functional surface to a TIN surface.

Answer 15

Creating TIN Surfaces

Question 16

An advanced surface creation technique that is most useful when there is a spatially correlated distance or directional bias in the data.

Answer 16

Kriging

Question 17

Surface Feature Types to Build a TIN Surface

Answer 17

1. Mass Points
2. Breaklines and Hulls
3. Polygon Surface Feature Types

Question 18

________ are point height measurements; they
become the nodes in the TIN network.

Answer 18

Mass Points

Question 19

________ are the primary input into a TIN and determine the overall shape of the surface,

Answer 19

Mass Points

Question 20

________ are lines with or without height
measurements and become sequences of one of more triangle edges.

Answer 20

Breaklines

Question 21

________ typically represent either ridgelines or streams, or built features such as roadways.

Answer 21

Breaklines

Question 22

Kinds of Breaklines

Answer 22

1. Hard Breaklines
2. Soft Breaklines

Question 23

________ represent a discontinuity in the slope of the surface and capture abrupt changes in a surface (e.g. streams and road cuts).

Answer 23

Hard Breaklines

Question 24

________ allow to add edges to a TIN to capture linear features that do not alter the local slope of a surface or to
capture their position without affecting the shape of the surface (e.g. study area boundaries).

Answer 24

Soft Breaklines

Question 25

________ are polygons that represent surface features with area such as lakes or boundaries of separately interpolated areas

Answer 25

Hulls

Question 26

Polygon Surface Feature Types

Answer 26

1. Clip polygons 1. Erase polygons 1. Replace polygons 1. Fill polygons

Question 27

________ inputs data that falls outside the clip polygon is excluded from the interpolation and analysis.

Answer 27

Clip polygons

Question 28

________ inputs data that falls within the erase polygon is excluded from the interpolation and analysis operations.

Answer 28

Erase polygons

Question 29

________ set the boundary and all interior heights to same value; used to model a lake or an area on a slope excavated to a level surface.

Answer 29

Replace polygons

Question 30

________ assigns an integer attribute value to all triangles that fall within the fill polygon; surface height is unaffected, and no clipping or erasing takes place.

Answer 30

Fill polygons

Question 31

________ involves several kinds of processing, including extracting new surfaces from existing surfaces, reclassifying surfaces and combining surfaces.

Answer 31

Analyzing Surfaces

Question 32

A bare earth raster grid referenced to a vertical datum.

Answer 32

Digital Elevation Model (DEM)

Question 33

A vector data set composed of regularly spaced points and natural features such as ridges and breaklines.

Answer 33

Digital Terrain Model (DTM)

Question 34

This captures the natural and built features on the Earth’s surface and is useful in 3D modeling.

Answer 34

Digital Surface Model (DSM)

Question 35

Terrain Analysis Tools

Answer 35

1. Slope 1. Aspect 1. Hillshade 1. Curvature

Question 36

This calculates the maximum rate of change from a cell to its neighbors, which is typically used to indicate steepness of terrain.

Answer 36

Slope

Question 37

This calculates the direction in which the plane fitted to the slope faces for each cell.

Answer 37

Aspect

Question 38

* shows the intensity of lighting on a surface given a light source at a particular location. * it can model which parts of a surface would be shadowed by other parts. * creates a shaded relief from a surface raster by considering the illumination source angle and shadows.

Answer 38

Hillshade

Question 39

This calculates the slope of the slope, that is, whether a given part of a surface is a convex or concave.

Answer 39

Curvature

Question 40

Visibility Tools

Answer 40

Line of Sight Observer Points Viewshed

Question 41

This identifies whether or not one location is visible from another, and whether or not the intervening locations along a line between the locations are visible.

Answer 41

Line of Sight

Question 42

This tool identifies which observers, specified as a set of points, can see any given cell of a surface.

Answer 42

Observer Points

Question 43

This tool calculates, for each cell of a raster surface and a set of input points, how many observers can see any given cell.

Answer 43

Viewshed