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E-CONTENT
Practical Core Course THEMATIC CARTOGRAPHY (GRB CC 202)
COMPILED AND DESIGNED BY SABA KHANAM DEPARTMENT OF GEOGRAPHY
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E-CONTENT COMPILED AND DESIGNED BY SABA KHANAM
UNIT III
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E-CONTENT COMPILED AND DESIGNED BY SABA KHANAM
CARTOGRAPHIC OVERLAYS
The objects in a spatial database are representations of real-world entities with associated attributes. The power of a GIS comes from its ability to look at entities in their geographical context and examine relationships between entities. thus a GIS database is much more than a collection of objects and attributes. in this unit we look at the ways a spatial database can be assembled from simple objects. For e.g. how are lines linked together to form complex hydrologic or transportation networks. For e.g. how can points, lines or areas be used to represent more complex entities like surfaces?
POINT DATA
1. the simplest type of spatial object 2. choice of entities which will be represented as points depends on the scale of the map/study 3. e.g. on a large scale map - encode building structures as point locations 4. e.g. on a small scale map - encode cities as point locations 5. the coordinates of each point can be stored as two additional attributes 6. information on a set of points can be viewed as an extended attribute table each row is a point - all information about the point is contained in the row each column is an attribute two of the columns are the coordinates overhead - Point data
here northing and easting represent y and x coordinates each point is independent of every other point, represented as a separate row in the database model
LINE DATA
Infrastructure networks transportation networks - highways and railroads utility networks - gas, electric, telephone, water airline networks - hubs and routes canals
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Natural networks river channels
AREAL DATA
Areal Data is represented on area class maps, choropleth maps boundaries may be defined by natural phenomena, e.g. lake, or by man, e.g. forest stands, census zones there are several types of areas that can be represented
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DIGITAL CARTOGRAPHY
"Cartography is the art and technique of map reproduction. It is in a narrower sense to be characterized as a refining process between the original source material and the reproduction." (Eduard Imhof,1962)
A map is a scale representation of a geographical environment.
Digital cartography is also called digital mapping. It is the process by which a collection of data is compiled and formatted into a virtual image. The primary function of this technology is to produce maps that give accurate representations of a particular area, detailing major road arteries and other points of interest. The technology also allows the calculation of distances from one place to another. Digital Cartography involves the creation and analyses of maps through the use of computers. As such, Geographical Information Systems (GIS) are an integral tool for Cartography. Thus Digital cartography is the technology concerned with the construction and use of computer-based systems for the practice of cartography and its applications.
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Although digital mapping can be found in a variety of computer applications the main use of these maps is with the Global Positioning System, or GPS satellite network, used in standard automotive navigation systems.
DATA COLLECTION
Digital maps heavily rely upon a vast amount of data collected over time. Most of the information that comprise digital maps is the culmination of satellite imagery as well as street level information. Maps must be updated frequently to provide users with the most accurate reflection of a location. While there is a wide spectrum on companies that specialize in digital mapping, the basic premise is that digital maps will accurately portray roads as they actually appear to give "life-like experiences."
FUNCTIONALITY AND USE
COMPUTER APPLICATIONS
Proprietary and non-proprietary computer programs and applications provide imagery and street-level map data for much of the world.
SCIENTIFIC APPLICATIONS
The development of mobile computing (PDAs, tablet PCs, laptops, etc.) has recently (since about 2000) spurred the use of digital mapping in the sciences and
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E-CONTENT COMPILED AND DESIGNED BY SABA KHANAM applied sciences. As of 2009, science fields that use digital mapping technology include geology (see Digital geologic mapping), engineering, architecture, land surveying, mining, forestry, environmental, and archaeology.
The GPS receiver then utilizes position to provide GPS coordinates, or exact points of latitudinal and longitudinal direction from GPS satellites. The points, or coordinates, output an accurate range between approximately "10-20 meters" of the actual location.
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The beginning point, entered via GPS coordinates, and the ending point, (address or coordinates) input by the user, are then entered into the digital mapping software. The mapping software outputs a real-time visual representation of the route. The map then moves along the path of the driver. If the driver drifts from the designated route, the navigation system will use the current coordinates to recalculate a route to the destination location.
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