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Active Sonar- transducers emit an acoustic signal or pulse of sound into the water. If an object is in the path of the sound pulse, the sound bounces off the object and returns an echo to the sonar transducer. If the transducer is equipped with the ability to receive signals, it measures the strengt...

Active Sonar- transducers emit an acoustic signal or pulse of sound into the water. If an object is in the path of the sound pulse, the sound bounces off the object and returns an echo to the sonar transducer. If the transducer is equipped with the ability to receive signals, it measures the strength of the signal. By determining the time between the emission of the sound pulse and its reception, the transducer can determine the range and orientation of the object. Areas- stored as set of mathematically connected X,Y coordinates defining the boundary (vector) or as set of contiguous cells defining the interior (raster). Azimuthal (planar) Projection- result from projecting a spherical surface onto a plane. Best for polar or circular regions, direction always true from center. Bathymetric LIDAR- uses water-penetrating green light to also measure seafloor and riverbed elevations. Cartography – the science that deals with the construction, use, and principles behind maps and map use. Conic Projection- result from projecting a spherical surface onto a cone. Best for mid- latitudes with an East- West orientation like Canada. Coordinate systems- enable geographic datasets to use common locations for integration. Cylindrical Projection- longitudes equally spaced, latitudes unequally spaced, scale is true along equator, shape and scale distortions increase near poles, shows true direction, universal Traverse Mercator (UTM). Data Accuracy- termed as the discrepancy between the actual attributes value and coded attribute value. Data Completeness- is the measure of totality of features. Data Consistency- termed as the absence of conflicts in a particular database. Data Precision- precision can be termed as the degree of details that are displayed on a uniform space. Digital Elevation Model (DEM)- is generated by feature extraction from high resolution stereo satellite imagery. Ellipsoid- a mathematical model of the size and shape of the earth. Geodesy- science of measuring the earth. Geographic Information System (GIS)- It combines location and information about the location, ability to analyze information, analyze as many layers of information at once and can overlay different spatial information at once. Geoid- a theoretical surface generally defined as mean sea level. Used as the basis for a vertical datum and as reference for a horizontal datum. Geostationary Orbit – a geostationary orbit is one in which the satellite is always in the same position with respect to the rotating Earth. Global or Spherical Coordinate System-such as latitude, longitude. These are often referred to as geographic coordinate systems. Horizontal Datum- a spheroid used as an (X,Y) reference to all points on the real globe. Interferometric synthetic aperture radar (IFSAR)- data to generate Digital Elevation Models (DEMs), this radar mapping technology is an effective tool for collecting data under challenging circumstances such as cloud cover, extreme weather conditions, rugged terrain, and remote locations. This geodetic method uses two or more synthetic aperture radar (SAR) images to generate maps of surface deformation or digital elevation, using differences in the phase of the waves returning to the satellite. Latitude- imaginary lines that runs horizontally, degrees latitude are numbered from 0 to 90 north and south, the equator is the imaginary line that divides the north and south hemisphere and also known as parallels since they are parallel and are equal distant from each other (69 miles or 111 km apart). Light Detection and Ranging (LIDAR)- is a remote sensing method that uses light in the form of a pulsed laser to measure ranges (variable distances) to the Earth. These light pulses— combined with other data recorded by the airborne system— generate precise, three-dimensional information about the shape of the Earth and its surface characteristics. A LIDAR instrument principally consists of a laser, a scanner, and a specialized GPS receiver. Airplanes and helicopters are the most used platforms for acquiring LIDAR data over broad areas. Light detection and Ranging (LiDAR)- is an active sensor that measures ground height. Using light from an airplane or helicopter platform, it measures the time it takes to bounce back to the sensor. From this, you can create Digital Surface Models which is useful in forestry. Lines- stored as a set of mathematically connected X,Y coordinates (vector) or as a set of connected grid cells (raster). Longitude- imaginary lines that runs vertically and also known as meridians. They converge at the poles and are widest at the equator (69 miles or 111 apart). 0 degree refer to Prime Meridian located at Greenwich England and continues 180 degrees east and west where they meet and form the International Date line in the Pacific Ocean. Luzon 1911- is a geodetic datum first defined in 1911 and is suitable for use in Philippines onshore. Luzon 1911 references the Clarke 1866 ellipsoid and the Greenwich prime meridian, origin is Fundamental point: Hinanggayon, Marinduque. Latitude: 13°33'41.000"N, longitude: 121°52'03.000"E (of Greenwich). It is a geodetic datum for Topographic mapping and it was defined by information from Coast and Geodetic Survey Replaced by Philippine Reference system of 1992 (datum code 6683). Map Legend- the legend is the key to read a map, provides essential information for the map reader. Map Projection- is used to portray all or part of the round Earth (3D) on a flat surface (2D) map. All map projections distort the surface in some fashion. A map or parts of a map can show one or more, but never all of the following: – True Directions – True Distances – True Areas – True Shapes. Map Scale- ratio between distance on a paper map and distance of the same stretch in actual terrain. Passive Sonar- systems are used primarily to detect noise from marine objects (such as submarines or ships) and marine animals like whales. Passive sonar does not emit its own signal, which is an advantage for military vessels that do not want to be found or for scientific missions that concentrate on quietly listening to the ocean. Rather, it only detects sound waves coming towards it. Passive sonar cannot measure the range of an object unless it is used in conjunction with other passive listening devices. Multiple passive sonar devices may allow for triangulation of a sound source. Philippine Transverse Mercator coordinate system- reduces distortion by creating a series of central meridians. Local series of projections designed primarily for collecting survey data in the Philippines (Zone I 117° East Area west of 118° E), ( Zone II 119° East Palawan and Calamian Islands), (Zone III 121° East Luzon (except SE), Mindoro), (Zone IV 123° East SE Luzon, West Mindanao ), (Zone V 125° East East Mindanao, Bohol, Samar). Points- stored as individual X,Y coordinates (vector) or as individual column, row cell entries in a grid (raster). Polar orbit/Sun-Synchronous Orbit - an orbit that goes over both the North and the South Pole. Primary Sources- those collected in digital format specifically for use in a GIS project by direct measurement. Typical examples of primary GIS sources include raster satellite images, and vector building-survey measurements captured using a total survey station. Projected Coordinate System- based on a map projection, such as transverse Mercator, which provide various mechanisms to project maps of the earth's spherical surface onto a twodimensional Cartesian coordinate plane. PRS92 or the Philippine Reference System of 1992- a homogeneous national network of geodetic control points (GCPs), marked by concrete monuments or mojons, that has been established using Global Positioning System (GPS) technology – NAMRIA. It is a local projection designed specifically for the Philippines and primarily used for surveying political boundaries. Radar system- consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects. RAdio Detection And Ranging or RAdio Direction And Ranging (RADAR)- is an objectdetection system that uses radio waves to determine the range, angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. Radio waves- (pulsed or continuous) from the transmitter reflect off the object and return to the receiver, giving information about the object's location and speed. Raster- single square cells. Each cell will have a value corresponding to its land cover type. Represents features as a matrix of cells in continuous space. Reference system- used to represent the locations of geographic features, imagery, and observations such as GPS locations within a common geographic framework. Remote Sensing- gathering information about something (object) without being in any contact with it. Resolution- the accuracy with which a given map scale can depict the location and shape of map features. The smaller the map scale the, the higher the possible resolution. Resolution plays a large role in GIS, especially in raster – based modelling. Satellite- orbit around the earth has a sensor which scans the Earth's surface measuring the amount of light reflected/transmitted. Secondary Sources- those reused from earlier studies or obtained from other systems. Typical secondary sources include raster scanned color aerial photographs of urban areas and paper maps that can be scanned and vectorized (digitized). Sensor- a device that measures a certain energy level of the electromagnetic spectrum and converts it into a signal which can be read by an instrument. Sensors are developed to measure a certain amount of energy dependent on the usage. Shuttle Radar Topography Mission (SRTM)- uses inSAR which measures Earth’s elevation with two antennas. In only a couple days, SRTM has collected one of the most accurate digital elevation models of earth. Has a product of 90m DEM data sets for orthorectification of satellite image data. Sound Navigation and Ranging (SONAR)- is helpful for exploring and mapping the ocean because sound waves travel farther in the water than do radar and light waves. Spatial information – information associated with an underlying geography, or description of location. Spatial Reference Framework- combination of factors; ellipsoid, geoid, datum, coordinate system and projection that identify a point on a sphere and on a two-dimensional representation of the sphere. Spatial resolution – the minimum size of objects that can be detected by a sensor system. Spheroid- slightly non-spherical object, but not necessarily mathematical definable. Surveying- science of identifying and measuring the specific locations on the earth. Topographic LIDAR -uses a near-infrared laser to map the land. Vector- points, lines / routes, polygons / regions, TINs (triangulated irregular networks). Vertical Datum- level surface to which heights (elevation) are referenced.