Unit seven. Getting the map into the computer

Vocabulary notes :

tangible - ясный, осязаемый, реальный

virtual - виртуальный, допускаемый,

фактический, текущий

to force - вынуждать, принуждать

to fold - складывать, перегибать

Ex .1 Read and translate the text.

Most people think of maps as drawings on paper. Maps hang on walls, lie in map drawers, and fill the pages of books, atlases, street guides, newspapers, and magazines. Maps roll off the nation's printing presses in the millions each year, and they fill the spaces in every car's glove compartment, neatly folded or not! The traditional paper maps of our everyday world can be called real maps, because they are touchable. We can hold them in our hands, fold them up, and carry them around. The computer, in contrast, has forced us to reconsider this simple definition of a map. In the digital era, and especially within GISs, maps can be both real and virtual.

A virtual map is a map waiting to be drawn. It is an arrangement of information inside the computer in such a way that we can use the GIS to generate the map however and whenever we need it. We may have stored map information about roads, rivers, and forests, for example, but may decide that only the forests and rivers need be shown on any map that the GIS produces. Every real map is simply a conversion of the virtual map into a medium, the form that the map will take. In most cases, the medium we use is paper.

Ex. 2 Answer the following questions using the information from the text.

1. What do we call a real map ?

2. What is a virtual map ?

3. What is the medium for both types of maps ?

Ex. 3 Read and translate key terms and their definition.

analog: A representation where a feature or object is represented in another tangible

medium. For example, a section of the earth can be represented in analog by a paper

map, or atoms can be represented by Ping-Pong balls.

attribute: A characteristic of a feature that contains a measurement or value for the

feature. Attributes can be labels, categories, or numbers; they can be dates, standardized values, or field or other measurements. An item for which data are collected and organized. A column in a table or data file.

geocoding: The conversion of analog maps into computer-readable form. The two usual methods of geocoding are scanning and digitizing.

real map: A map that has been designed and plotted onto a permanent medium such as paper or film. It has a tangible form and is a result of all of the design and compilation decisions made in constructing the map, such as choosing the scale, setting the legend, choosing the colours, and so on.

virtual map: A map that has yet to be realized as a tangible map; it exists as a set of possible maps. For example, the same digital base map and set of numbers can be entire series of possible virtual maps, yet only one may be chosen to be rendered as a real map on a permanent medium.

Ex. 3 Read the text . Decide whether the statements are true (T) or false(F).

FINGING DATA ON THE NETWORKS

An excellent way to begin a data search is to use a computer network. Several computer packages allow you to do this over the various network access methods, such as America Online and CompuServe. The most sophisticated tools, however, are those available on the Internet. Among the various tools, such as Archie, Veronica, WAIS, and Gopher, is a computer program called Mosaic, from the National Supercomputing Center at the University of Illinois. Mosaic allows you to search the World Wide Web (WWW), an interlinked set of computers and servers, or data repositories on the Internet. Similar and more widely used programmes are Netscape Navigator and Microsoft Explorer. Each major agency has a World Wide Web server, or gateway, through which data can be searched and downloaded. Simply enormous amounts of data are available through this simple mechanism.

1. Existing map data are used in a map library. ( )

2. A data search is provided by various network access methods. ( )

3. The Internet is of great help in finding data. ( )

4. Mosaic is an interlinked set of computers and servers. ( )

5. We search data through a World Wide Web server but download

the data through a simple mechanism. ( )

Ex. 5 Read the text. Find the English equivalents to the terms below :

Using maps within GISs means that somehow they have already been turned from real into virtual maps. Another way to say this is that a paper map has gone through a conversion, from a paper or analog form into a digital or number form. We start with paper, or sometimes film, Mylar, or some other medium, and we end up with a set of numbers inside files in the computer. This conversion process is called geocoding, which we can define as the conversion of spatial information into computer-readable form. Some GIS vendors would be pleased to help you acquire the data you need but at an immense price. Studies have shown that finding the right maps, and converting these maps from real to virtual form by geocoding, takes up anywhere between 60% and 90% of both the time and money spent on a typical GIS project. Fortunately, this is a once-only cost. As soon as we have the map in a digital form, we can use it in a GIS over and over again for different uses and projects unless it needs an update.

1. претерпели преобразование _______________________________

2. (майларовая) пленка _______________________________

3. пространственная информация _______________________________

4. считываемый компьютером _______________________________

5. огрoмная цена _______________________________

6. единоразовые затраты _______________________________

7. обновление _______________________________

8. продавец ГИС _______________________________

Ex. 6 Translate the sentences into English :

1. Данные для ГИС можно

а. купить.

б. найти в цифровом виде в существующих источниках.

в. собрать (capture) по аналоговым картам путем геокодирования.

2. Геокодирование – это преобразование пространственной (spatial)информации

в цифровую форму.

3. Геокодирование включает в себя сбор (capturing) данных по карте и

нахождение атрибутов.

4. Данные, имеющиеся на существующих картах, можно найти в библиотеке

карт, через поисковую сеть (network searches), либо на носителях

информации, например, на CD-ROM или дисках.

5. Большинство провайдеров обеспечивают доступ к информации через

всемирную сеть.

Ex. 7 Read the text and translate it in writing into Russian.

Digital map data for use in GIS really falls into two categories. Either the data already exist and all we have to do is find or buy them, or they don't exist and we have to geocode paper maps or maps on some other medium. A third case is that the maps don't even exist, and here we often turn to remote sensing, aerial photography, or field data collection by surveyors or the global positioning system (GPS), to get our first map of a new location. Also, sometimes the maps we need already exist, but whoever geocoded them is not interested in sharing the data with you, even for a price! Even when we can get the maps we need in digital form, they may not suit our particular type of GIS, or may be out of date or not show the features we want. Sooner or later, and usually sooner, we end up geocoding at least some of our own maps.

UNIT EIGHT. DIGITIZING AND SCANNING

Ex. 1 Read and translate key terms and their definitions.

digitizing: Also called semi-automated digitizing. The process in which geocoding takes place manually; a map is placed on a flat tablet, and a person traces out the map features using a cursor. The locations of features on the map are sent back to the computer every time the operator of digitizing tablet presses a button.

scanning: A form of geocoding in which maps are placed on a surface and scanned by a light beam. Reflected light from every small dot or pixel on the surface is recorded and saved as a grid of digits. Scanners can work in black and white in gray tones or in color.

digitizing tablet: A device for geocoding by semiautomated digitizing. A digitizing tablet looks like a drafting table but is sensitized so that as a map is traced with a cursor on the tablet and the locations are identified, converted to numbers, and sent to the computer.

Ex. 2 Read the text. Find the new terms given above. Translate the text orally.

DIGITIZING AND SCANNING

Historically, many different means have been used to geocode. At first, some very early GIS packages required maps to be encoded and entered by hand. The hours of monotonous work required for this task made errors common and their correction dif­ficult. Since special-purpose digitizing hardware became available, and especially since the cost of this hardware fell substantially, virtually all geocoding has been performed by computer.

Two technologies have evolved to get maps into the computer. Digitizing mim­ics the way maps were drafted by hand and involves tracing the map over using a cursor

while it is taped down onto a sensitized digitizing tablet. The second method involves having the computer ‘sense’ the map by scanning it. Both approaches work and have their advantages and disadvantages. Most important, the method of geocoding stamps its form onto the data in such a way that many other GIS operations are affected afterwards.

Ex. 3 Answer the questions using the information from the text.

1. How were the early GIS packages encoded at first ?

2. What was the disadvantage of encoding by hand ?

3. What two methods were involved to get maps into the computer ?

Ex. 4 Examine FIGURE 4 and discuss the digitizing procedure.

1. Digitizer cursor transmits a pulse from an electromagnetic coil under the view

lens.

2. Pulse is picked up by nearest grid wires under tablet surface.

3. Result is sent to computer after conversion to x and y units.

FIGURE 4. Digitizing tablet system of operation.

Ex. 5 Now read the text about digitizing. Find the English equivalents to the terms given below.

DIGITIZING

Geocoding by tracing over a map with a cursor is sometimes called semiautomated digitizing. This is because in addition to using a mechanical device, it involves a human operator. Digitizing means the use of a digitizer or digitizing tablet (Figure 4). This technology has developed as computer mapping and computer-aided design have grown and placed new demands on computer hardware.

The digitizing tablet is a digital and electronic equivalent of the drafting table. The major components are a flat surface, to which a map is usually taped, and a sty­lus or cursor, with the capability of signaling to a computer that a point has been selected (Figure 4). The mechanism to capture the location of the point can differ. Many systems have connected arms, but most have embedded active wires in the tablet surface that receive an electrical impulse sent by a coil in the cursor. In some rare cases, the cursor transmits a sound, which is picked up and recorded by an array of microphones.

1. чертежный стол ___________________________

2. устройство преобразования в цифровую форму__________________________

3. цифровой преобразователь графической информации

__________________________

4. манипулятор ___________________________

5. поверхность ___________________________

6. встраивать ___________________________

7. зд. плотно приклеивать с помощью ленты ___________________________

8. пишущая игла __________________________

Ex. 6 Continue reading about digitizing. Now guess what the words in italics mean or find the meaning of these words in your dictionary.

The beginning of the digitizing sequence involves selecting the control points and interactively entering their world coordinates. This is a very important step, because an error at this stage would lead to an error in every pair of coordinates. After the map is taped to the tablet, it should not be moved without entering the control points again, and it is preferable to perform this step only once per map. Ideally, the entire digitizing process should be finished at one sitting.

Tape should be placed at each map corner after smoothing the map, and care should be taken to deal with folds and the crinkles that develop with certain papers during periods of high humidity. A stable base product such as Mylar or film is preferable for digitizing. The lower edge, which will have the cursor and your right sleeve (if you are right-handed) dragged over it many times, should be taped over its entire length. You should always permanently record the x and y values of the map control points, ideally digitally and with the geocoded data set. This may allow later recovery of lost resolution or systematic errors.

Ex. 7 Now read the text about scanning. Find the English equivalents to the terms given below.

SCANNING

The second digitizing process is automated digitizing or more usually, just scanning. The scanner you may have seen at a computer store or in an advertisement, or perhaps the one you use for scanning documents, is a desktop scanner. The drum

scanner is most commonly used for maps. This type of scanner receives an entire sheet map, usually clamped to a rotating drum, and scans the map with very fine increments of distance, measuring the amount of light reflected by the map when it is illuminated, with either a spot light source or a laser. The finer the resolution, the higher the cost and the larger the data sets. A major difference with this type of digitizing is that lines, features, text, and so on, are scanned at their actual width and must be preprocessed for the computer to recognize specific cartographic objects. Some plotters can double as scanners, and vice versa.

For scanning, maps should be clean and free of folds and marks. Usually, the scanned maps are not the paper products but the film negatives, Mylar separations, or the scribed materials that were used in the map production. An alternative scanner is the automatic line follower, a scanner that is manually moved to a line and then left to follow the line automatically. Automatic line followers are used primarily for continuous lines, such as contours. These and other scanners are very useful in CADD (computer-aided drafting and design) systems, where input from engineering drawings and sketches is common.

1. настольный сканер ____________________

2. барабанный сканер ____________________

3. шаг, увеличение ____________________

4. местный (локальный) источник света ____________________

5. графопостроитель ____________________

6. увеличивать в два раза ____________________

7. предварительно обрабатывать, подготавливать____________________

8. материалы с разметкой ____________________

9. автоматическая следящая строка ____________________

10. контур, очертание ____________________

Ex. 8 Translate the following sentences into English.

1. Метод геокодирования может влиять на построение карты (structure) и

повлечь за собой ошибки, связанные с пространственной информацией.

2. Двумя основными методами геокодирования являются преобразование в

цифровую форму и сканирование.

3. При преобразовании в цифровую форму данные снимаются (capture) с

карты путем отслеживания (tracing) линий вручную.

4. При сканировании карта размещается (place) на стеклянной плоскости

(plate), которая освещается лучoм света.

5. Для сканирования важны размер изображения и разрешение (resolution).

Ex. 9 Read the text and translate it in writing into Russian.

FIELD DATA COLLECTION

An increasing amount of data for GIS projects comes from a combination of field data, global positioning system data, and imagery. Field data are collected using standard sur­veying methods, in which locations are established in the field as control points and then additional locations, tracing out features or covering terrain, for example, are traced out by large numbers of measurements using instruments designed to measure angles and distances. The highest accuracy instruments, called total stations are digital recorders as well as measurement instruments and use laser ranging to prism reflectors to calculate distance.

UNIT NINE. DATA ENTRY

Ex. 1 Read and translate the text.

Geocoding is the part of GIS data input that results in getting a map into the computer. It is not the entire story, however, for as yet we have not dealt with getting the attributes into the GIS. An attribute is a value, usually a number, containing information about the features contained in the GIS. If the feature we are geocoding is a road, for example, then capturing the route of the road from a map as it winds from intersection to intersection is pure geocoding. We also have to tell the computer what this long and winding line is: a road, and anything else that the GIS needs to know about it. Relevant attributes for a road might be its state route number, the year it was built, what the surface is made of, how many traffic lanes are on the road, if the road is one-way or two-way, how many bridges it goes over, how many cars travel along the road per hour, and so on. These values are the road's attributes. They are the very meat and potatoes of GIS analysis.

Somehow, we have to get them into the computer, too.

Ex. 2 Answer the questions using the information from the text.

1. What does getting the map into the computer result from ?

2. What is an attribute ?

3. What is necessary for GIS analysis ?

Ex. 3 Read and translate key terms and their definitions.

data entry: The process of entering numbers into a computer, usually attribute data. Although most data are entered by hand, or acquired through networks, from CD-ROMs, and so on, field data can come from a GPS (global positioning system) receiver, from data loggers, and even by typing at the keyboard.

data-entry module: The part of a database manager that allows the user to enter or edit records in a database. The module will normally both allow entry and modification of values, and enforce the constraints placed on the data by the data definition.

drop-out: The loss of data due to scanning at coarser resolution than the map features to be captured. Features smaller than half the size of a pixel can disappear entirely.

drum scanner: A map input device in which the map is attached to a drum that is rotated under a scanner while illuminated by a light beam or laser. Reflected light from the map is then measured by the scanner and recorded as numbers.

editing: The modification and updating of both map and attribute data, general using a software capability of the GIS.

flat file: A simple model for the organization of numbers. The numbers are organized as a table, with values for variables as entries, records as rows, and attributes as columns .flatbed scanner: A map input device in which the map is placed on a glass surface, and the scanner moves over the map, converting the map into numbers.

network: Two or more computers connected together so that they can exchange

messages, files, or other means of communication. A network is part hardware, usually cables and communication devices such as modems, and part software.

server: A computer connected to a network whose primary function is to act as a

library of information that other users can share.

stream mode: A method of geocoding in semi-automated digitizing, in which a contin­uous stream of points follows a press of the cursor button. This mode is often used for digitizing long features such as streams and coastlines. It can generate data very quickly, so is often weeded out immediately by automated line generalization within the GIS.

Ex. 4 Read the text. Decide whether the following statements are true (T) or false (F).

The simplest way to think of attributes is in a flat file. A flat file is really like a table of numbers. The columns of the table are the attributes, and the rows of the table are the features themselves. Each line in the table is a record, but the name used depends on who you talk to. A computer scientist would call a row of tuple, a statistician would call it a case or an observation. A programmer might call it an instance of a geographic object. They are all pretty much the same. Record sounds more simply.

Take a look at the flat file in FIGURE 5. The records and attributes relate to the example we discussed above, a road. The attribute table then consists of several parts. First, it has attributes with their names. Setting up attributes means deciding what values are going to be associated with each our features. At the time of setup, it is easy to anticipate something we may want to collect in the future and to leave a column in the table.

Second, there are records. A record usually has a value in every one of the columns. Software programmes such as spreadsheets and some databases allow you to click into a cell in the table and put in a value. Nevertheless, setting up the table has to be a little more formal than that.

ID	Feature	Name	Surface	Lanes	Traffic per hour
1	Road	US 11	tarmac	3	1 13
2	Road	I 81	c oncrete	4	432
3	Road	Lisk Bridge Road	tarmac	2	12

value, is the number attribute has a name record, all

or text associated and a value for each attributes for