Skills Training on Appraisal of Specific Types of Real Proper ty and Other Special Cases of Appraisal Practice Iloilo Grand Hotel, Iloilo City
Geographical Information System
A Quick Math Review: Numbers
Radio astronomers in at the National Radio Observatory in Green Bank, Virginia, USA are pointing giant saucer-shaped antennas at the 2 stars – Tau Ceti and Epsilon Eridani – to listen for mathematically organized beeps.
This effort underscores a quality of universality in mathematics that everyone feels but no one knows how to define.
For many of the world’s greatest thinkers, intoxicated by this indefinable something, mathematics represents absolute truth.
A Quick Math Review: Numbers
Plato: “God ever geometrizes.”
Carl Gustav Jacob Jacobi: “God ever arithmetizes.”
Sir James Jeans: “The Great Architect of the Universe now begins to appear as a pure mathematician.”
Bertrand Russell: “Mathematics is the subject in which we never know what we are talking about nor whether what we are saying is true.”
A Quick Math Review: Numbers ďƒ’
This Promethean boast is saying that mathematics can apply to our world and universe because it is designed to apply to every possible world and universe that might be imagined along logical lines.
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Mathematics reaches into a realm of such ultimate sophistication that the truth or non-truth of any given premise no longer matters.
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What matters is that the premise be correctly reasoned to its conclusion.
A Quick Math Review: Numbers
Today, no one can balance his check book without applying arithmetic invented by the ancient Mesopotamians and Hindus.
No one can build a wall without drawing on techniques of geometric measurement developed by Egyptian mathematicians.
It was Greek pioneers of geometry who conceived the idea that the earth might have the shape of a sphere.
The mathematical and scientific investigations of Galileo and Newton led to the building of machines that churned the Industrial Revolution.
A Quick Math Review: Numbers
Nuclear research draws heavily on Einstein’s Theory of Relativity
The 2 Pillars of Mathematics in antiquity were: 1.
Arithmetic – the science of numbers
2.
Geometry – the science of shapes and spatial relationships
Algebra is the arithmetic shorthand when unknown quantities were involved.
In the 17th Century, arithmetic and algebra were unified with geometry in “analytic geometry” – a technique for mapping numbers as points on a graph.
A Quick Math Review: Numbers
Analytic geometry converted equations into geometric shapes, and converted shapes into equations – it clarified one branch of mathematics in terms of another and opened the way to most of the disciplines of higher mathematics – encompassed by the single word – “analysis”.
Calculus was the first offspring of analysis. It is a system for analyzing change and motion in terms of points or numbers strung together in continuous sequences.
A Quick Math Review: Numbers
Below are some of the myriad uses of calculus: Enables
scientists to solve problems in dynamics – the ripple of a wave, the arc of a shooting star, the continuing behavior of every moving thing.
A Quick Math Review: Numbers
By studying gambling games, mathematicians discovered the laws of probability – the uncertainty that lurks in almost any sequence of events. Help
set the rate a person must pay on an insurance policy
Enable
pollsters to estimate, from any given sampling of voters, the chances of making an accurate election forecast.
Evaluate
statistically the buckshot patterns which millions of invisible subatomic particles make when they strike a target at the muzzle end of an atom smasher.
A Quick Math Review: Numbers
Yet, other mathematicians find inspiration in the most elementary of mathematical ideas – number theory. Counting
is the most baffling, stimulating and entertaining of all mathematical subjects.
The
underlying processes of thought itself have become a target for mathematical probes.
The
meanings of nouns and verbs used in human reasoning may be replaced with symbols.
Proponents
of symbolic logic have reduced all objects of human study into sets and groups – collections of thoughts or things that go together logically.
A Quick Math Review: Numbers
Human fingers and toes are the handiest counters – which amassed numbers up to 20.
As fingers and toes ran out, a 20-based number system was developed, such as the British 20-shilling pound and the French word for 80 - “quatre-vingt” which means “four-twenty”.
The British monetary system is a mixture of several archaic systems perpetuated to confound foreigners, such as half pennies, pennies, three pence, six pence, shillings, half crowns, pounds and guineas – a ½-1-3-612-30-240-252 system.
A Quick Math Review: Numbers
In whatever counting system, early merchants used pebbles to represent the numbers counted from which evolved a computing device called the “abacus” – which is still a standard equipment in bazaars from Tehran to Hongkong, today.
One of the crudest ways of writing numbers of writing numbers is preserved for us today in the Roman numerals I, II, III, IV, V, VI, etc.
The written symbols for numbers we use today – 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 originated from the Hindus.
This is a 10-based or decimal method of counting.
A Quick Math Review: Numbers
“Decima” is Latin for tenth or tithe.
The decimal system has a “positional notation” where numbers larger than 1 are separated from numbers smaller than 1 (fractions) by a decimal point.
To the left of the decimal point, the first digit is worth just itself; the next is worth 10 times itself, the next is 100 times itself, and so on.
To the right of the decimal point, the first digit is worth 1/10 of itself, the next is 1/100 of itself, and so on.
A Quick Math Review: Numbers
For example, the number 1,234.567 may be expressed as;
1 x 1,000 + 2 x 100 + 3 x 10 + 4 x 1 + 5 x 1/10 + 6 x 1/100 + 7 x 1/1,000
Thereafter, a shorthand version was invented – the so-called “power” and “exponent”. The number above may also be expressed as;
1 x 10³ + 2 x 10² + 3 x 10¹ + 4 x 10º + 5 x 10-¹ + 6 x 10-² + 7 x 10-³
Note: As 10º is equal to 1, any number raised to the zero power is equal to 1.
A Quick Math Review: Numbers
On the other hand, ancient Mesopotamians, who were avid astronomers, developed the “sexagesimal” or the 60-system. The base 60 fitted well with their division of a year into 360 days.
At around 1700 B.C., cuneiform tablets show that this is already being used for amazing feats of mathematical computation during the reign of Babylon’s intellectual King Hammurabi.
While 60 is a large number to use as a base for a notation system, we still use it today in dividing an hour into 60 minutes; a minute into 60 seconds; and a circle into 6 x 60º.
A Quick Math Review: Numbers
Finally, the 10-based system won out over earlier numbering systems.
The first great popularizer of the decimal positional notation was an Arab mathematician – al-Khowarizmi (825 A.D.) of Baghdad. It took about 2 centuries before this system reached Spain.
European merchants, most likely Araby-Indy experts in the counting houses of the shipping firms of Genoa and Hamburg found that they could do accounts faster than colleagues specializing in, say, Roman numerals.
A Quick Math Review: Numbers
The decimal point, as we know it today, made its debut in 1617 in a book by Scotsman John Napier.
Today, with all our knowledge, we have yet to settle on our final counting system. New creatures of man’s genius have emerged – robots and calculating machines. They operate by electric switches which can be either “on” or “off”.
As a result, they can only count 2 numbers: 1 for “on” and 0 for “off”.
Thus, modern man is now increasingly relying on a 2based or binary system of arithmetic.
A Quick Math Review: Numbers
Ironically, by the time we finally hear the mathematically organized “beeps” from outer space, we may have gone back to the counting simplicity of an aborigine, but we may have brought to it the enlightened understanding of an Einstein.
A Quick Math Review: Numbers
Man’s mechanical and electronic marvels designed to speed up calculating work;
1.
Napier’s bones – a simple device for multiplying popular in 17th Century Europe.
2.
Pascal’s adding machines – invented in 1642 by the French philosopher Blaise Pascal, then, 19 years old and tired of totting up figures for his tax collector father.
3.
Difference engine – designed by the 19th Century English inventor Charles Babbage to calculate and print mathematical tables.
A Quick Math Review: Numbers
Man’s mechanical and electronic marvels designed to speed up calculating work;
4.
Differential analyzer – invented by Dr. Vannevar Bush, is a giant modern mechanical computer built in 1930 at M.I.T. to solve differential equations. This was used to calculate artillery trajectories during World War II.
5.
First data processing machine – perfected the use of punched cards by American engineer Herman Hollerith in 1890.
6.
ENIAC – the first electronic computer developed in 1946 at the University of Pennsylvania can add in 1/5000 of a second.
A Quick Math Review: Numbers
Man’s mechanical and electronic marvels designed to speed up calculating work;
7.
STRETCH (IBM) – the largest U.S. Computer today; owned by the Weather Bureau, it can add in 1.5 millionth of a second.
8.
UNIVAC 1824 – is a powerful miniature computer utilizing monolithic crystals and weighing only 17 pounds, it can automatically pilot a missile, satellite or spaceship.
A Quick Math Review: Numbers 1.
2.
The Four Steps in Computer “Thinking”: Input
Like the human brain, the computer must be given the problem and the information it needs to solve it.
Punched cards are one of the commonest means of feeding information into the computer.
No hole – 0; hole – 1
Memory
All the information a computer needs to solve a problem – and just how it is to use that information – is stored in the computer’s memory units.
One type of memory is made of many units in which wires form a grid with tiny, circular core magnets strung at each intersection.
Counter clockwise field – 0; clockwise field – 1
A Quick Math Review: Numbers 3.
5.
The Four Steps in Computer “Thinking”: Processing
In processing, the computer solves its problem. Unlike a human brain, it acts only by rote, using logic provided by a human programmer.
The first computers used vacuum tubes in their processing units. Modern computers use faster and smaller transistorized circuits.
No current – 0; current – 1
Output
The voice of the computer, its output, produces answers in many forms: punched cards, punched tape, magnetic tape, typewritten sheets of paper, etc.
Geographical information system ďƒ’
Cogent Reasons for Using Computers in Car tography: 1.
To make existing maps more quickly.
2.
To make existing maps more cheaply.
3.
To make maps for specific user needs.
4.
To make map production possible in situations where skilled staff are unavailable.
5.
To allow experimentation with different graphical representation of the same data.
6.
To facilitate map making and updating when the data are already in digital form.
7.
To facilitate analyses of data that demand interaction between statistical analysis and mapping.
8.
To minimize the use of the printed map as a data store and thereby minimize the effects of classification and generalization on the quality of the data.
9.
To create maps that are difficult to make by hand, e.g. 3-D maps or stereoscopic maps.
10.
To create maps in which selection and generalization procedures are explicitly defined and consistently executed.
11.
Introduction of automation can lead to a review of the whole map-making process, which can also lead to savings and improvements.
Geographical information system
“Computer cartography is like a person with the body of an athlete in his prime time and the mind of a child” (Poiker 1982).
“Cartographers still have the belief that the only use of computer assisted cartography is as an aid to the “penpushing” copying of maps” (Boyle 1981).
“The poverty of the technique, if it is indeed impotent to deal with its presumed subject matter, is hidden behind a mountain of effort ... the harder the sub-problems were to solve, and the more technical success was gained in solving them, the more is the original technique fortified” (Weizenbaum 1976).
Geographical information system ďƒ’
Geographical information systems are the result of linking parallel developments in many separate spatial data processing disciplines.
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Parallel developments in automated data capture, data analysis, and presentation in several broadly related fields, such as, cadastral and topographic mapping, thematic cartography, civil engineering, geography, mathematical studies of spatial variation, soil science, surveying and photogrammetry, rural and urban planning, utility networks, and remote sensing and image analysis underwent technical and conceptual development over time.
Geographical Information System
Figure 1. GIS Linkages
Geographical information system ďƒ’
Geographical data describe objects from the real world in terms of:
1.
Their position with respect to a known coordinate system.
2.
Their attributes that are unrelated to position (e.g. color, cost, pH, incidence of disease, etc.)
3.
Their spatial interrelations with each other (topological relations), which describe how they are linked together or how one can travel between them.
Geographical information system ďƒ’
Three Components of a GIS:
1.
Computer hardware
2.
Sets of application software modules
3.
Organizational content
Geographical information system ďƒ’
Computer hardware a.
Central processing unit (CPU)
b.
Digitizer
c.
Plotter
d.
Tape drive
e.
Disk drive
f.
Visual display unit (VDU)
Geographical Information System
Figure 2. Major Hardware Components
Geographical information system ďƒ’
GIS sof tware modules: these are technical subsystems for: a.
Data input and verification
b.
Data storage and database management
c.
Data output and presentation
d.
Data transformation
e.
Interaction with the user
Geographical Information System
Figure 3. Main Software Components of a GIS
Geographic Information System
Figure 4. Data Input
Geographical Information System
Figure 5. Components of the Geographical Database
Geographic Information System
Figure 6. Data Output
Georgraphical Information System
Figure 7. Data Transformation
Geographical Information System ďƒ’
Interaction with the user (general questions) 1.
Where is object A?
2.
Where is A in relation to place B?
3.
How many occurrences of type A are there within distance D of B?
4.
What is the value of function Z at position X?
5.
How large is B (area, perimeter, count, etc.)?
6.
What is the result of intersecting various kinds of spatial data?
7.
What is the path of least cost, resistance, or distance along the ground from X to Y along pathway P?
8.
What is at points X1, X2, ...?
9.
What objects are next to objects having certain combination of attributes?
10.
Reclassify objects having certain combinations of attributes.
11.
Using the digital database as a model of the real world, simulate the effect of process P over time T for a given scenario S.
Geographical Information System
The Organizational Aspects of GIS In
order to be used effectively, the GIS needs to be placed in an appropriate organizational context.
It
is not sufficient for an organization to purchase a computer and some software and to hire or retrain one or two enthusiastic individuals and then expect instant success.
New
tools can only be used effectively if they are properly integrated into the whole work process and not tacked on as an afterthought.
Geographical Information System
Figure 8. Organizational Aspect of GIS
Gis terminology
Acceptance test. A test for evaluating a newly purchased system’s performance and conformity to specifications.
Access time . A measure of the time interval between the instant that data are called from storage and the instant that delivery is complete.
Addressable point. A position on a visual display unit (VDU) that can be specified by absolute coordinates.
Algorithm. A set of rules for solving a problem.
Alphanumeric code. Machine processable letters, numbers, and special characters.
Analog. A continuously varying electronic signal.
Application. A task addressed by a computer system.
Archival storage. Magnetic media used to store programs and data outside the normal addressable memory units of the computer.
Area. A fundamental unit of geographical information.
Array. A series of addressable data elements in the form of a grid or matrix.
Automated car tography. The process of drawing maps with the aid of computer driven display devices such as plotters and graphics screens.
Back-up. Making a copy of a file or a whole disk for safe keeping in case the original is lost or damaged.
Gis terminology
BASIC. Beginner’s All-purpose Symbolic Instruction Code.
Batch processing. The processing of a group of similar jobs on the computer without operator intervention.
Binar y arithmetic. The mathematics of calculating in powers of two.
Bit. The smallest unit of information that can be stored or processed in a computer.
Bit map. A pattern of bits on the grid stored in memory and used to generate an image on a raster scan display.
Bits per inch (BPI). The density of bits recorded on a magnetic tape.
Boot up. To start up a computer system.
Bug. An error in a computer program or in a piece of electronics that causes it to function improperly.
Bulk memor y. An electronic device such as disks or tapes that allow the storage of large amounts of data.
Bus. A circuit, or group of circuits that provide a communication path between the computer and peripherals.
Byte. A group of contiguous bits, usually eight, that represent a character and which are operated on as a unit.
CAD. Computer-Aided Design.
Gis terminology
Cathode ray tube (CRT) . An electronic screen for displaying information or graphics.
Cell. The basic element of spatial information in the raster (grid) description of spatial entities.
Central processing unit (CPU). The part of the computer that controls the whole system.
Chain. A sequence of coordinates defining a complex line or boundary.
Character. An alphabetical, numerical or special graphic symbol that is treated as a single unit of data.
Characters per second (CPS). A measure of the speed with which a device can process data in the form of characters.
Choropleth map. A map consisting of areas of equal value separated by abrupt boundaries.
Code. A set of specific symbols and rules for representing data and programs so that they can be understood by the computer.
Colour display. A CRT capable of displaying maps and results in colour.
Command. An instruction sent from the keyboard or other control device to execute a computer program.
Composite map. A single map created by joining together several separately digitized maps.
Gis terminology
Computer graphics. A general term embracing any computer activity that results in graphic images.
Computing environment . The total range of hardware and software facilities provided by a given make of host computer and its operating system.
Configuration. A particular combination of computer hardware and software for a certain class of application tasks.
Console. A device that allows the operator to communicate with the computer.
Contour. A line connecting points of equal elevation.
Cross-hatching. The technique of shading areas on a map with a given pattern of lines or symbols.
Cursor. A visible symbol guided by the keyboard, a joystick, a tracking ball, or a digitizer, usually in the form of a cross or a blinking symbol, that indicates a position on a CRT.
Database. A collection of interrelated information, usually stored in some form of mass storage system such as magnetic tape or disk. A GIS database includes data about the position and the attributes of geographical features that have been coded as points, lines, areas, pixels or grid cells.
Database management system (DBMS) . A set of computer programs for organizing the information in a database.
Gis terminology
Data link. The communication lines and related hardware and software systems needed to send data between two or more computers over telephone lines, optical fibres, satellite networks, or cables.
Debug. To remove errors from a program or from hardware.
Debugger. A program that helps a programmer to remove programming errors.
Device. A piece of equipment external to the computer designed for a specific function such as data input, data storage, or data output.
Digital. The ability to represent data in discrete, quantized units or digits.
Digital elevation model (DEM). A quantitative model of landform in digital form; also known as digital terrain model (DTM).
Digitizer. A device for entering the spatial coordinates of mapped features from a map or document to the computer.
Disk. A storage medium consisting of a spinning disk coated with magnetic material for recording digital information.
Diskette. A cheap, low capacity storage medium, usually measuring 3 ½,
5 ½, or 8 inches in diameter; also known as floppy disk.
Distributed processing. The placement of hardware processors where needed, instead of concentrating all computer power in a large central CPU.
Gis terminology
Dot-matrix plotter . A plotter of which the printing head consists of many, closely spaced (100 – 400 per inch) wire points that can write dots on the paper to make a map; also known as matrix plotter.
Drum plotter. A device for plotting maps in which the Y-axis movements are governed by the rotation of the drum.
Drum scanner . A device for converting maps to digital form automatically.
Edit. To remove errors from, or to modify a computer file of a program, a digitized map or a file containing attribute data.
Element. A fundamental geographical unit of information, such as a point, line, area, or pixel; also known as entity.
Extrapolation . The act of extending results of spatial sampling to points outside the area surveyed.
File. A collection of related information in a computer that can be accessed by a unique name.
Filter. In raster graphics, a mathematically defined operation for removing long-range (high-pass) or short range (low-pass) variation. Used for removing unwanted components from a signal or spatial pattern.
Floppy disk. Also known as diskette.
Gis terminology
Flatbed plotter . A device for drawing maps whereby the information is drawn by the plotting head being moved in both the X and Y directions over a flat, fixed surface. Draws with a pen, light beam, or scribing device.
Font. Symbolism used for drawing a line or representing typefaces used for displaying text.
Format. The way in which data are systematically arranged for transmission between computers, or between a computer and a device.
FORTRAN. Formula translation.
Fourier analysis . A method of dissociating time series or spatial data into sets of sine and cosine waves.
Gap. The distance between two graphic entities (usually lines) on a digitized map. Gaps may arise through errors made while digitizing or scanning the lines on a map.
Geocoding. The activity of defining the position of geographical objects relative to a standard reference grid.
GIMMS. Geographic Information Manipulation and Mapping Systems; a well-known low-cost polygon mapping GIS.
Grey scales. Levels of brightness (or darkness) for displaying information on monochrome display devices.
Gis terminology
Grid. 1. A network of uniformly spaced points or lines on the CRT for locating positions. 2. A set of regularly spaced sample points. 3. In cartography, an exact set of reference lines over the earth’s surface. 4. In utility mapping, the distribution network of the utility resources, e.g. electricity or telephone lines.
Grid map. A map in which the information is carried in the form of grid cells.
Hard copy. A copy of a graphics or map originally displayed on a CRT.
Hardware. The physical components of a GIS – the computer, plotters, CRT’s, etc.
Hierarchical database structure . A method of arranging computer files or other information so that the units of data storage are connected by a hierarchically defined pathway. From above to below, relations are one-to-many.
Host computer. The primary, or controlling computer in a data network.
Hypsometr y. The measurement of the elevation of the earth’s surface with respect to sea level.
Input. (Noun) the data entered to a computer system; (Verb) the process of entering data.
Input device. A hardware component for data entry.
Integer. A number without a decimal component.
Interactive. A GIS system in which the operator can initiate or modify program execution and receive information from the computer.
Gis terminology
Inter face. A hardware and software link that allows two computer systems, or a computer and its peripherals to be connected together for data communication.
Interpolate. To estimate the value of an attribute at an unsampled point from measurements made at surrounding sites.
Isopleth map. A map displaying the distribution of an attribute in terms of lines connecting points of equal value.
Jaggies. Jargon term for curved lines that have a stepped or saw-tooth appearance in a display device.
Join. (Verb) to connect two or more separately digitized maps; (Noun) the junction between two such maps, sometimes visible as a result of imperfection in the data.
Joystick . A hand-controlled lever for controlling the movement of the cursor on a graphics CRT.
Justification (lef t. Right, or center). The relative position of a text string or symbol on the map to the location at which it has been digitized.
Keyboard. A device for typing alphanumeric characters into the computer. The arrangement of the keys resembles that of a typewriter.
LANDSAT. The generic name for a series of earth resource scanning satellites launched by the United States of America.
Gis terminology
Layer. A logical separation of mapped information according to theme.
Line. One of the basic geographical elements, defined by at least two pairs of XY coordinates.
Machine. A computer.
Machine language . Instructions coded so that the computer can recognize and execute them.
Magnetic media . Tape or disks coated with a magnetic surface used for storing electronic data.
Mainframe . A large computer supporting many users.
Map. Cartography; a hand drawn or printed document describing the spatial distribution of geographical features in terms of a recognizable and agreed symbolism. Digital; the collection of digital information about a part of the earth’s surface.
MAP (Map Analysis Package). A computer program written by C.D. Tomlin for analyzing spatial data coded in the form of grid cells.
Map generalization . The process of reducing detail on a map as a consequence of reducing the map scale.
Map projection . The basic system of coordinates used to describe the spatial distribution of elements in a GIS.
Gis terminology
Menu. In interactive graphics stations, a set of programmed areas on the digitizing tablet.
Microcomputer . A small, low cost computer.
Minicomputer. A medium-sized, general purpose single processor computer often used to control GIS.
Modelling. 1. The representation of the attributes of the earth’s surface in a digital database. 2. The studying of landscape processes using mathematical algorithms written in computer code.
Modem (modulator demodulator). A device for the interconversion of digital and analog signals to allow data transmission over telephone lines.
Module. A separate and distinct piece of hardware or software that can be connected with other modules to form a system.
Mouse. A hand-steered device for entering data from a digitizer.
Multispectral scanner system (MSS). A device, often carried in airplanes and satellites, for recording received radiation in several wavebands at the same time.
Network. 1. Two or more interconnected computer systems for the implementation of specific functions. 2. A set of interconnected lines (arcs, chains, strings) defining the boundaries of polygons.
Gis terminology
Network database structure. A method of arranging data in a database so that explicit connections and relations are defined by links or pointers of a many-to-many type.
Node. The point at which arcs (lines, chains, strings) in a polygon network are joined. Nodes carry information about the topology of the polygon.
Noise. Irregular variations, usually short range, that cannot be easily explained or associated with major mapped features or process.
Numerical taxonomy . Quantitative methods for classifying data using computed estimates of similarity.
Object code. A computer program that has been translated into machine readable code by a compiler.
Operating system (OS). The control program that coordinates all the activities of a computer system.
Output. The results of processing data in a GIS, maps, tables, screen images, tape files.
Overlay. 1. Programming; the process of replacing a segment of code in the computer memory. 2. Mapping; the process of stacking digital representations of various spatial data on top of each other so that each position in the area covered can be analyzed in terms of these data.
Gis terminology
Package. A set of computer programs that can be used for a particular generalized class of applications.
Paint. To fill in an area with a given symbolism on a raster display device.
PASCAL. A high-level programming language that is been used increasingly instead of FORTRAN for scientific programming.
Pen plotter. A device for drawing maps and figures using a computer-steered pen.
Per formance. The degree to which a device or system fulfils its specifications.
Peripheral. A hardware device that is not part of the central computer.
Pixel. Contraction of picture element; smallest unit of information in a grid cell map or scanner image.
Plotter. Any device for drawing maps and figures.
Polygon. A multi-sided figure representing an area on a map.
Post-processor. A computer program that is used to convert the results of another operation into a standard format ready for further analysis.
Precision. 1. Degree of accuracy; generally refers to the number of significant digits of information to the right of the decimal point. 2. Statistics; the degree of variation about the mean.
Program. A precise sequential set of instructions directing the computer to perform a task.
Gis terminology
Quadrant. A quarter of a circle measured in units of 90 degrees.
Raster. A regular grid of cells covering an area.
Raster database. A database containing all mapped, spatial information in the form of regular grid cells.
Raster display. A device for displaying information in the form of pixels on a CRT.
Raster map. A map encoded in the form of a regular array of cells.
Raster-to-vector. The process of converting an image made up of cells into one described by lines and polygons.
Real numbers. Numbers that have both an integer and a decimal component.
Real time. Tasks of functions executed so rapidly that the user gets an impression of continuous visual feedback.
Record. A set of attributes relating to a geographical entity; a set of unrelated contiguous data in a computer file.
Redundancy. The inclusion of data in a database that contribute little to the information content.
Refresh tube. A raster CRT in which the information is continuously refreshed or redrawn by the electron guns in a manner similar to a normal television screen. Consequently, refresh tubes can display motion.
Region. A set of points having a certain value as an attribute in common.
Gis terminology
Resampling . A technique for transforming a raster image to a particular scale and projection.
Resolution. The smallest spacing between two display elements; the smallest size of feature that can be mapped or sampled.
Response time . The time that elapses between sending a command to the computer and the receipt of the results at the workstation.
Run-length code . A compact method of storing data in raster databases.
Scale. The relation between the size of an object on a map and its size in the real world.
Scanner. A device for converting images from maps, photographs, or from part of the real world into digital form automatically.
Simulation. Using the digital model of the landscape in a GIS for studying the possible outcome of various processes expressed in the form of mathematical models.
Sliver. The gap between two lines, created erroneously by a scanner and its raster-vector software.
Smoothing. A set of procedures for removing short-range, erratic variation from lines, surfaces, or data series.
Sof tware . General name for computer programs and programming languages.
Gis terminology
Source code. A computer program that has been written in an English-like computer language. It must be compiled to yield the object code before it can be run on the computer.
Spike. An overshoot line created erroneously by a scanner and its raster-vector software.
Spline. A mathematical curve used to represent spatial variation smoothly.
SPOT. An earth resource satellite with high resolution sensors launched by France in February 1986.
Stereo plotter. A device for extracting information about the elevation of landform from stereoscopic aerial photographs. The results are sets of X, Y, and Z coordinates.
Storage. The parts of the computer system used for storing data and programs.
Storage tube. A CRT used for displaying graphics information that retains the image continuously; cannot display motion.
String. A set of X-Y coordinate pairs defining a group of linked line segments.
SYMAP. Synagraphic Mapping Program . The original grid-cell mapping program developed by Howard T. Fisher at Harvard.
SYMVU. A program for drawing perspective views of three-dimensional data.
Syntax. A set of rules governing the way statements can be used in a computer language.
Gis terminology
Tablet. A small digitizer used for interactive work on a graphics workstation.
Tape drive . A device for reading and writing computer files on magnetic tape.
Terminal. A device, usually including a CRT and a keyboard, for communicating with a computer.
Text editor . A program for creating and modifying text files.
Thematic map. A map displaying selected kinds of information relating to specific themes, such as soil, land-use, population density, suitability for arable crops, etc.
Tile. A part of the database in a GIS representing a discrete part of the earth’s surface.
Topographic map. A map showing the contours, roads, rivers, houses, etc. in great accuracy and detail relative to the map scale used.
Topology. The way in which geographical elements are linked together.
Utility mapping . A special class of GIS applications for managing information about public utilities such as water pipes, sewerage, telephone, electricity, and gas networks.
Vector. A quantity having both magnitude and direction.
Window. A usually rectangular area that is used to view or transform the original map
Zero. The origin of all coordinates where the X, Y, and Z axes intersect.
Zoom. A capability for enlarging or reducing the scale of a figure displayed on a CRT.
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