Landscape Modeling Glossary

Landscape Modeling

Glossary

 

This list contains terms from a variety of distinct disciplines -- including computer graphics, modeling and rendering, image processing, landscape architecture, and geographical analysis -- all of which may be encountered in the process of landscape modeling and creating digital visualizations. Many terms common in those disciplines have been omitted; this selective list contains terms used throughout (or at least once in) this book and the sense(s) in which they are used.

 

A B C D E F G H I J K L M N O P Q R S T U V W XYZ

 

2.5D surface: a simple 3D surface with no overhangs or holes (specifically, for each (x,y) location there is only a single z value); includes many 3D terrain surfaces, but not all

2D: having two dimensional geometry, flat, characterized by Cartesian (x,y) coordinates

3D: having three dimensions, characterized by Cartesian (x,y,z) coordinates

3D digitizer: a device used to capture and record 3D coordinates from real life objects

 

A

aerial oblique: a view taken from above looking down at an angle, as from an airplane

airlight: the lightening of the atmosphere with distance caused by particles reflecting sunlight

albedo: a measure of the brightness of a reflective object or surface

algorithm: a formula or series of steps carried out by an agent such as a person or computer

allee: a linear arrangement of trees, usually lining a street, canal or other feature

alpha channel: a separate layer, or map, embedded within a raster image file format, used to carry additional information per pixel; often used for transparency information

ambient light: surrounding or environmental light that is everywhere equally intense and has no directionality

amplitude: intensity or height of a wave between peak and trough

analog: continuous, real, not discrete or sampled; contrast with digital

and: logical or boolean operator that creates the intersection set

angle of repose: the maximum vertical angle at which a pile of loose material is stable

anti-aliasing: a technique in computer graphics of adding in pixels of intermediate values at high-contrast edges to reduce the "jagged" appearance of diagonal lines

array: a repetitive arrangement, usually linear, rectangular, or circular / concentric

aspect: the direction a surface is "facing", such as east or southeast; also called orientation

aspect ratio: of a rectangle, or rectangular object such as an image or pixel, the ratio of width (x-axis) to height (y-axis)

atmospheric haze: the phenomenon of blueing and lightening of the atmosphere at a distance, caused by airlight and particular matter or water vapor

AVI: Audio Video Interleave; a file format for multimedia and animations developed by Microsoft Corporation

 

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B

base data: the original source data, such as maps or other measurements or plans, on which a project (landscape, architectural or geographic) is based, and from which other data (e.g. slope, or intermediate layers) are derived

berm: a mound of earth, often linear

billboard: a transparent rectangular plane, used in computer graphics rendering to carry a 2D image used to represent a 3D object such as a tree in the landscape

bitmap: in general, a digital raster image; sometimes limited to a raster image with only two color values (monochrome), typically black and white

Boolean: a logical system or algebra using set theory and operators such as "and", "or" and "not", the basis of binary computers and some solid modeling operations, described by and named after the mathematician George Boole

bosque: a rectangular or circular grove of trees in a regular planting arrangement

bump map: a 2D image used in computer rendering to produce the appearance of depth, or "bumps", in a multi-channel texture-mapped image

 

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C

CAD: Computer Aided Design or Computer Aided Drawing software, designed for creating digital representations of 2D and 3D objects and space;typically contains modeling and/or rendering functions, as well as import, export, and others

caustic: the characteristic sinuous, curved, shiny light rays seen on underwater surfaces, caused by refraction through the rippled top surface of water

CAVE: Computer Augmented Visualization Environment, a room or chamber with multiple displays (often six or more projectors or rear-projection screens) used to create an immersive "virtual reality" environment

cell: in a raster representation, a pixel or repeated regular element

cell size: the typical width, height, or sometimes area of a cell in a raster grid

cirrus: kind of cloud

CLUT: Color LookUp Table, a data structure used in indexed color images to correspond color values to numeric values

CMYK: Cyan, Magenta,Yellow and Black color system, used when printing with inks; contrast with RGB

contour interval: in a contour plan, the typical vertical distance between contour lines

contour line: an imaginary line, or isoline, connecting points of equal elevation above some fixed level, or datum; used to represent 3D curved surfaces such as terrain

contour plan: a representation of a smooth 3D or 2.5D surface, using contour lines

contrast: in an image or scene, the amount of difference between the lightest and darkest areas

cumulous: kind of cloud

cut: dirt, or other earth material, removed in a grading operation; or to the act of removing, or to the area where material has been removed

cut and fill: the process of removing earth material from some locations and adding it to others by grading; the process of computing total volumes of material moved

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D

datum: a fixed or established point of reference, usually with a fixed elevation

decal: a 2D image or texture map applied to an object in a computer rendering, like a label on a bottle

deLauney triangulation: a method of connecting an arbitrary set of points together in a network of triangles which meet certain mathematical criteria (specifically, the circle described by the three points in any triangle contains no other point in the set), used in creating a TIN

DEM: Digital Elevation Model, any digital representation of the earth’s surface, but also a particular raster grid format used by the USGS and others

depth of field: the zone in which an image seen through a lens is in perfect focus

diffuse: light which is indirect, and has no reflections or highlights, similar to ambient

digital: encoded in binary integers (bits), discretized or sampled, typically on or for a computer; contrast with analog

digital ortho quad: (DOQ) a digital map produced by the USGS which contains the information found on a typical USGS "quad sheet" map, orthorectified and geo-referenced

digitizing: generally the process of making digital, but also specifically using a "digitizer" to trace coordinates, 2D or 3D, of an object and create a digital representation

directional light: light which has a location and direction; contrast with ambient light

DLG: Digital Line Graph, a digital format used by the USGS for vector data

DOQ: see digital ortho quad

DPI: dots per inch, used to measure the resolution of images either on screen or on paper

drape: to project an image, or 3D vector features, onto a 3D surface such as a digital model of terrain, to create a realistic representation, much as a flexible sheet can be draped over an irregular surface, conforming to it

SDTS: Spatial Data Transfer Standard, a conventional standard format for transferring geographic data used by the USGS

DTM: Digital Terrain Model; synonym for DEM

DV: Digital Video; a format for storing digital moving images, equivalent to, but with higher image resolution than, analog video

DVD: Digital Versatile Disc, a format and optical medium for storing large amounts (2-5 GB) of digital data, commonly used for storing digital video

DXF: Data Exchange Format, a proprietary but widely used digital file format for describing 2D and 3D spatial data, developed by Autodesk Corporation

 

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E

edge: in computer graphics, a line segment between two end points, or vertices; three or more edges combine to make faces or polygons

elevation: usually, referring to terrain data, meaning height above sea level; but also a paraline drawing of an object or scene as seen from the side

 

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F

face: in computer graphics, a flat 2D bounded area or polygon, formed by at least three connected edges; at least four faces are required to make up a solid polyhedron

field of view: (FOV) the angle of the cone of vision of a lens; the usual human FOV is approximately 150°

fill: dirt, or other earth material, added in a grading operation; or to the act of adding, or to the area where material has been added

floating point: a digital representation of a number with a specified number decimal places, or fractional part, used to represent real numbers; contrast with integer

flow accumulation: a measurement of the amount of water accumulated in overland flow over a surface

fly-over: an animation made from an aerial point-of-view, such as from an airplane

FOV: see field of view

fractal: an algorithm, or shape, characterized by self-similarity and produced by recursive sub-division; more generally the branch of mathematics named and explored by Benoit Mandelbrot

 

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G

geo-reference: to assign accurate real-world coordinates in some map projection to the geometric representation of some object(s), or to at least the corners, and usually all points or contents, of a map, image or photograph

geospecific: computer renderings created using photographs or other images (satellite, e.g.) which are geo-referenced and so can be used to drape over digital terrain models for realistic visualizations

geo-TIFF: a file format for images, which contains geo-referencing information

geotypical: visualizations which are created by inserting "typical" elements such as generic houses, trees, etc., in appropriate locations, determined by geographic data, so as to make realistic but non-specific visualizations

GIS: Geographic Information System; software designed to store, manipulate and display geographic and spatial data such as maps

God rays: visible rays of light, caused by particles in the atmosphere or underwater, sometimes called “crepuscular rays” at sunset

GPS: Global Positioning System or Satellite, a satellite-based system for determining precise geographic locations in the field

grading: the process of moving earth material for functional or aesthetic purposes; also the process of designing or creating a grading plan

grading plan: a document, often a contour plan, which directs a grading process

grid mesh: a representation of raster data produced by drawing lines between successive grid cell centers or corners; also called a "fish-net"

 

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H

hard shadows: shadows created by light from a single source, causing shadows with a solid interior and sharp distinct edges, cast by the umbra; contrast with soft shadows

HDTV: High Definition Television; a format for video images characterized by a 16:9 image aspect ratio and high resolution imagery

heads-up digitizing: the process of tracing outlines from a raster image, on-screen

height field: a raster elevation model

hypsography: description of underwater surfaces using contour lines

 

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I

IGES: Initial Graphics Exchange Standard,a proposed standard digital file format for computer graphics and spatial data

image-map: a digital raster image, used in rendering to give color or texture to 3D objects

immersion: a method for projecting images such that the viewer’s peripheral vision is engaged, either by using head mounted displays or CAVE techniques

indexed color: a data structure for representing color images using a color lookup table, capable of a smaller number of total colors than the RGB system

integer: a numeric value with no decimal places, used to represent whole numbers

intersection: the set-theoretic operation yielding only those elements that are contained in each of two operand sets, equivalent to the logical "and"

inverse kinematics: a technique for creating models of mechanical linkages of connected parts, such that motion is transmitted in a predictable way through the parts.

 

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J

JAVA: an object-oriented programming language developed by Sun Microsystems

JPEG (or JPG): a file format for image data enabling "lossy compression", i.e. which may lose some detail when decompressed

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L

level of detail: a name for the phenomenon that real-world objects may need to be represented with varying amounts of detail – typically less in the distance, and more in the foreground or nearby – for reasons of computational efficiency

 

LOD: see level of detail

L-systems: Lindenmeyer systems, an algorithmic method of generating branched forms and structures such as plants

lux: lumens per square meter, a measurement of light intensity

 

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M

map: in computer graphics, a 2D raster image which serves as an image or texture in rendering, particularly in a multi-channel texture

map projection: a mathematical formula for converting points on a sphere, such as the earth, onto a plane, such as a flat map

mask: in computer graphics, an image with only two values (black and white) used in conjunction with another more detailed image to mask out, or clip, parts of the image, so as to indicate areas of transparency, or edges of the image, etc.

Mercator projection: a particular and early map projection in common use especially for navigational maps

mesh: a digital representation of a surface or solid consisting of multiple, possibly curved, line segments whose intersections form a regular grid

meta-balls: a digital modeling technique for representing "blobby" shapes as aggregations of spheres and an interpolated smoothly curved surface covering them

metadata: data about data, such as the source, date, accuracy and other attributes

MIP-map: from "Multi in Parvo", a digital data format that stores images at multiple different representations, in hierarchically nested scales such as 4x4, 16x16 and 256x256 pixels, so that different resolutions can be displayed at different distances from the viewer

model: a representation used as a surrogate for some real thing, for the purpose of testing, modifying, presenting, etc.

modeling: in computer visualization, the processes of creating the data structures used to represent objects and scenes, usually using special-purpose software; distinct from the process of "rendering" to create images

morph: to transform a shape image or object smoothly from an initial state to a different final state; also called "tweening" (from the presence of “in-between” states)

MOV: a file format for Quicktime movies and animations, developed by Apple Computer Co.

MPEG (or MPG): a file format for compressed video

multi-channel: in computer graphics, refers to textures composed of multiple "maps" or channels which describe different aspects of the optical properties of the texture, such as diffuse color, reflectivity, transparency, bump, etc.

Back to Top NTSC: National Televison System Committee; a common format for video signals, with a 4:3 aspect ratio and lower resolution than the newer HDTV

 

NURB: Non-Uniform Rational B-spline, a mathematical technique for representing smooth curved surfaces

 

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O

or: logical or boolean operator that creates the union set

orientation: synonym for aspect

ortho-photo: an aerial photograph that has been ortho-rectified and geo-referenced

ortho-rectify: the process of adjusting a photograph (typically aerial) to account for distortions introduced by camera, lens, and the topography of the earth’s surface to create an image with a constant horizontal scale

 

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P

paraline: a form of drawing projection which preserves distances and angles in the projection; includes plan, section, axonometric and isometric drawings but not perspective projection

parametric: characterized by having one or more variables, or parameters, which can be varied for different results or effects

patch: a curved surface with a rectangular border, or outline; patches may be combined together to create compound curved surfaces

penumbra: that portion of a shadow in semi-shade between the darkest, or umbra, and the un-shadowed zone

perspective: a drawing projection that portrays the convergence of parallel lines in the visual field and the apparent reduction in size of distant objects; the closest drawing projection to what the human eye experiences

photo-realism: the effort to create synthetic images such as computer renderings, indistinguishable from photographs of real objects or scenes

phototropism: the tendency of plans to move or grow towards light

pixel: a "picture element" or single point of color in a raster image

planting plan: a document, often a drawing superimposed upon a grading plan, showing locations, sizes and species of new plants in a proposed planting design

point cloud: a set of 3D points describing the outlines or surface features of an object, such as produced by a 3D digitizer

polyline: a line created by a series of shorter straight line segments

procedural: synonym for algorithmic

procedural texture: an image, used as a texture map, generated "on the fly" by a procedure, or algorithm

projection: the process of transforming 3D points in to 2D points, to create a drawing or image; see also map projection

 

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Q

QTVR: QuickTime Virtual Reality, a file format developed by Apple Computer Co. to represent 360° panoramic views, animations and hypertext links in a single file

Quicktime: a digital technology and file format for animations, developed by Apple Computer Co.

 

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R

radiosity: a technique for simulating lighting effects by considering the inter-reflections between surfaces in a 3D model, more computationally demanding than ray-tracing

raster: a rectangular array of values, or cells, or pixels; a common data format for representing and displaying maps and images

ray-tracing: a technique for simulating lighting effects in a rendering by mathematically casting light-rays into a 3D model, and computing reflection, refraction, and other effects

rectification: the process of transforming a map or an image by systematically moving individual elements, such as pixels or lines, to align with some other reference image or map; sometimes called "rubber-sheeting"

recursive: characterized by processes which can be indefinitely repeatedly applied to their own output, such as algorithms which create branching and subdivision

rendering: the process of creating an image meant to portray an object or scene, especially using computer graphics software; also the image so produced; distinct from the "modeling" operations which create the input for the rendering operations

RGB: Red,Green,Blue; a method for representing colors as mixtures of the three primary colors of light, especially for display on a computer screen or projector; contrast with CMYK

rubber-sheeting: see rectification

ruled surface: a faceted curved surface created by adjoining flat faces between two curved lines, created by subdividing each line into an equal number of short segments and connecting between them

 

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S

scotopic vision: the low-resolution, monochromatic vision of humans at night

self-similarity: the characteristic of certain natural and mathematically produced forms (fractals, e.g.) that they exhibit features which appear identical or similar at different scales of magnification

shadow map: a faster and less accurate alternative to ray-traced shadows for creating simulated shadows in a computer rendering

slope: measurement of the steepness of terrain, the ratio of vertical rise to horizontal distance expressed as a percentage or as degrees of angle

soft shadows: shadows created by light from multiple sources, causing multiple overlapping shadows and a region of intermediate gray values with fuzzy edges, cast by the penumbra; contrast with hard shadows

solid model: a digital representation of 3D objects which may have such attributes such as inside/outside, mass, volume, and others; contrast with surface model

specular: reflective, especially light from materials with glossy surfaces

spline: a curved line formed by two or more vertices, or "control points", and a mathematical formula describing the curve(s) between them

spot elevation: a specified 3D point with location and elevation, used to describe terrain, paving or other fixed floor elevations

State Plane projection: a map projection used by state governments in the United States

stratus: kind of cloud

surface model: a digital representation of 3D objects which have two sides and surface area, but no thickness, and so no attributes as inside/outside, mass, or volume; contrast with solid model

surface normal: the vector perpendicular to a surface or face at any point

swale: a ditch or valley in the earth

 

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T

texture map: a 2D raster image used in computer rendering to give color and other apparent surface characteristics ("textures") to 3D objects

TIFF (or TIF): a file format for color image data, which enables "loss-less compression"

tiling: regular repeated placement of a single small element covering a larger area or surface; especially an image or texture map used to cover a surface in rendering

TIN: Triangulated Irregular Network; a data format for representing surfaces as a connected network of triangles

transparency map: a 2D image or map, usually used in conjunction with other images in a multi-channel texture, to indicate transparency of an object in computer rendering; see alpha channel

tweaking: the process of moving individual vertices of 3D geometric object, such as a mesh or a TIN

 

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U

umbra: the darkest central portion of a shadow

union: the set-theoretic operation yielding all those elements that are contained in either of two operand sets, equivalent to the logical "or"

USGS: United States Geological Survey, the federal agency responsible for creating and disseminating detailed maps including topographic and land-use maps of the United States

UTM: Universal Transverse Mercator, a common map projection used for geographic data

 

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V

vector: a mathematical line segment with direction and magnitude; but more generally, any data representation that contains points, lines and polygons; contrast with raster

vertex: in computer graphics, a 2D or 3D point; two vertices may be connected together by a line, or edge

VHS: Video Home System; a common low-resolution format for recording video images; superceded by HDTV

virtual reality: simulated environments and the methods used to create them

visualization: the process of creating images using computers, also called "rendering" when applied to landscape or architectural material, instead of abstract scientific data; an image or images so produced

volume light: (sometimes “volumetric light”), light which is itself visible, usually in the form of rays emanating from the light source (e.g. sun, window or lamp), especially when an opaque object is in front of the light source; the effect in nature caused by particles in the atmosphere and obstructing objects such as clouds or mountains; see also “God rays”

VR: see virtual reality

VRML: Virtual Reality Modeling Language; a file format standard for representing 3D scenes especially for creating VR environments

 

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W

walk-through: an animation of a 3D scene made as if from a human eye-level

watershed: that area of land from which all water drains to a single specified “outfall” point

wire frame: a computer graphics representation of a 3D scene or object made only by colored lines representing the outlines, or edges, of objects, with no solid faces

WWW: World Wide Web, or simpley “web”, the common interface and conventions for navigation and communication over the Internet

 

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XYZ

X3D: a proposed standard for representing 3D objects and scenes combining aspects of the VRMLspecification with the XML standard

XML: a standard format for representing information, especially for transmission over the WWW

N

K

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