Lecture 3 - GIS and Remote Sensing.pdf

GIS, Remote Sensing GIS • Geographic Information System (GIS) ▪ It combines location and information about the location. ▪ Ability to analyze information ▪ Analyze as many layers of information at once ▪ Can overlay different spatial information at once GIS • Spatial information – information as...

GIS, Remote Sensing GIS • Geographic Information System (GIS) ▪ It combines location and information about the location. ▪ Ability to analyze information ▪ Analyze as many layers of information at once ▪ Can overlay different spatial information at once GIS • Spatial information – information associated with an underlying geography, or description of location • Cartography – the science that deals with the construction, use, and principles behind maps and map use Cartographic term 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 • Also known as parallels since they are parallel and are equal distant from each other (69 miles or 111 km apart) Cartographic term 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 Cartographic term Map Legend • The legend is the key to read a map. • It provides essential information for the map reader. Map Scale • Ratio between distance on a paper map and distance of the same stretch in actual terrain Cartographic term 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 • Spatial resolution – the minimum size of objects that can be detected by a sensor system Cartographic term Map Projection • A 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 Projection 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) Map Projection Conic Projection • Result from projecting a spherical surface onto a cone. • Best for mid- latitudes with an East- West orientation like Canada Map Projection Azimuthal (planar) Projection • Result from projecting a spherical surface onto a plane. • Best for polar or circular regions • Direction always true from center Coordinate System • Coordinate systems enable geographic datasets to use common locations for integration • Reference system used to represent the locations of geographic features, imagery, and observations such as GPS locations within a common geographic framework Coordinate system Two type • A global or spherical coordinate system such as latitude–longitude. These are often referred to as geographic coordinate systems • A 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 two-dimensional Cartesian coordinate plane. Coordinate system - Philippines 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). • a geodetic datum for Topographic mapping. • It was defined by information from Coast and Geodetic Survey Replaced by Philippine Reference system of 1992 (datum code 6683). Coordinate system - Philippines • PRS92 or the Philippine Reference System of 1992 is 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. Coordinate system - Philippines • PTM reduces distortion by creating a series of central meridians • Philippine Transverse Mercator coordinate system. 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 Types of data models 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. Types of data models Vector • Points • Lines / routes • Polygons / regions • TINs (triangulated irregular networks) Sources of data 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. 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). Spatial data quality • Data Completeness: It is the measure of totality of features. • Data Precision: Precision can be termed as the degree of details that are displayed on a uniform space • Data Accuracy: This can be termed as the discrepancy between the actual attributes value and coded attribute value • Data Consistency: Data consistency can be termed as the absence of conflicts in a particular database. Remote Sensing Remote Sensing definition • In its simplest form, remote sensing means gathering information about something (object) without actually being in any contact with it. Why remote sensing • Images taken from space/air permit us to see differences over time; to measure sizes, areas, depths, and heights; and in general, to acquire information that is difficult to acquire by other means Satellite • A satellite in orbit around the earth has a sensor which scans the Earth's surface measuring the amount of light reflected/transmitted. Satellite orbit • Geostationary orbit - A geostationary orbit is one in which the satellite is always in the same position with respect to the rotating Earth. • Polar orbit/Sun-Synchronous Orbit - An orbit that goes over both the North and the South Pole is called a Polar Orbit. Sensor • A sensor is a device t hat 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. Digital Elevation Model (DEM) Getting DEM • DEM is generated by feature extraction from high resolution stereo satellite imagery • Shuttle Radar Topography Mission (SRTM) has a product of 90m DEM data sets for orthorectification of satellite image data • Other remote sensing techniques are also utilized to get DEM, such as radar interferometry or LiDAR Digital Elevation Model (DEM) • The 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. • 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 IFSAR 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 Digital Elevation Model (DEM) IFSAR Digital surface model (DSM) Digital Terrain Model GIS and RS techniques for geology GIS Application: • Groundwater – Water quality mapping (interpolating) – Search for groundwater • Geohazard – Landslide susceptibility mapping (rainfall or landslide induced) – Flood susceptibility mapping (flood simulation) • Regional geology mapping – Landsat classification • Fault line mapping – Classification of SPOT images, Landsat images and the same images • Earthquake movement – Interferometry uses satellite data to visualize earthquake movement Satellite Imaging Earth observation satellites • Are satellites specifically designed for Earth observation from orbit, similar to spy satellites but intended for non-military uses such as environmental monitoring, meteorology, map making etc. • Google Earth RADAR RAdio Detection And Ranging or RAdio Direction And Ranging • is an object-detection 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. • A 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 object(s). • 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 LIDAR Light Detection and Ranging • 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, threedimensional 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 commonly used platforms for acquiring LIDAR data over broad areas. LIDAR Light Detection and Ranging • Two types of LIDAR are topographic and bathymetric. – Topographic LIDAR typically uses a near-infrared laser to map the land, while; – Bathymetric LIDAR uses water-penetrating green light to also measure seafloor and riverbed elevations. • LIDAR systems allow scientists and mapping professionals to examine both natural and manmade environments with accuracy, precision, and flexibility. SONAR Sound Navigation and Ranging • Is helpful for exploring and mapping the ocean because sound waves travel farther in the water than do radar and light waves. • Active Sonar – 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. SONAR Sound Navigation and Ranging • Is helpful for exploring and mapping the ocean because sound waves travel farther in the water than do radar and light waves. • Passive Sonar – Passive sonar systems are used primarily to detect noise from marine objects (such as submarines or ships) and marine animals like whales. Unlike active sonar, 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.