Geoinformatics - Study Notes
Lesson summary
Geoinformatics is the integration of remote sensing, the Global Navigation Satellite System (GNSS) and the Geographic Information System (GIS) dealing with spatial information. Together they have made significant changes in surveying and map making, and a basic understanding of them is crucial for surveys, navigation, hydrology and disaster management.
6.2 Remote sensing
Remote sensing is an integrated discipline of arts, science and technology that collects information about terrestrial objects using camera and sensor systems.
Elements of remote sensing
- Energy source: provides electromagnetic energy to the target; the sun is a major source.
- Radiation and the atmosphere: electromagnetic radiation propagates as wave motion. Scattering is its re-direction by suspended particles or large gas molecules; absorption is its uptake by gas molecules in certain spectral bands.
- Interaction with the target: reflected radiation is modified while it crosses the atmosphere.
- Recording of energy by the sensor: sensors are active or passive.
- Transmission, reception and processing: data are processed into an image. Image processing has three categories: image restoration, image enhancement and information extraction.
- Interpretation and analysis: examining images to identify objects and judge their significance, using tone, shape, size, pattern, texture, shadow and association.
Active and passive remote sensing
| Active | Passive |
|---|---|
| Generates its own energy | Depends on solar radiation |
| Microwave region; wavelengths longer than 1 mm | Visible and infrared region |
| Like a camera with a built-in flash | Like an ordinary camera |
| Fluorosensor, Synthetic Aperture Radar, laser-beam system | Captures data only in daylight |
Remote sensing platforms
- Ground borne: ladders, scaffolding, tall buildings, cranes, hand held devices, tripods and towers.
- Air borne: aircraft for low altitude and high altitude aerial remote sensing; balloons (first aerial images from a balloon in 1859; float at about 30 km); drones, miniature remotely piloted aircraft that give night and day data. The first known aerial photograph was taken in 1858 by Gaspar Felix Tournachon, "Nadar".
- Space borne: satellites; advantages are large area coverage, repetitive coverage, quantitative measurement, semi-automated processing and lower cost per unit area.
Types of satellites
| Type | Features | Examples |
|---|---|---|
| Geostationary | Equatorial, west to east, one revolution in 24 hours, covers 70 degrees N to 70 degrees S, one satellite views a third of the globe | GOES, METEOSAT, INTELSAT, INSAT, APPLE (India, 19 June 1981) |
| Polar or sun-synchronous | Orbits pole to pole; appears to shift westward as the earth rotates | LANDSAT, SPOT, IRS, NOAA, SEASAT, TIROS, HCMM, SKYLAB |
| Spy | Military and political purposes; photo reconnaissance, infrared telescopes, radars, SIGINT "ferrets" | Corona, MIDAS, SAMOS, Keyhole series, Gaofen 4 (China) |
Applications of remote sensing
Agriculture (crop identification, area and condition), forest management (fire, deforestation, encroachment), geology (lithological, structural and geomorphological mapping, mineral and hydrocarbon exploration), oceanography (bathymetry, chlorophyll, sediment), cartography, meteorology (radar weather data), topography and urban planning.
6.3 Geographic Information System
GIS emerged in the past two decades as an essential tool for urban and resource planning. Computer generations: vacuum tubes (1940-1956), transistors (1956-1963), integrated circuits (1964-1971), microprocessors (1972-2010) and artificial intelligence (from 2010).
- Components: hardware; software (ArcGIS, ArcView 3.2, QGIS, SAGA GIS, using RDBMS); data (attribute, spatial, remote sensing and global data base); people; methods (meta data documents them).
- Functions: data capture (digitization by manual digitizing or scanning), data storage (Generic Data Model; raster and vector), data manipulation (toolkits), and query and analysis, the heart of GIS.
6.4 Global Navigation Satellite System
GNSS is the collection of the world's global satellite based positioning systems. It can give centimetre level accuracy with error correction. The first satellite navigation system was Transit of the US military, based on the Doppler effect. GNSS satellites have a life of 5-7 years.
| System | Country | Key facts |
|---|---|---|
| GPS | United States | First GNSS; late 1970s; 24 satellites; global coverage |
| GLONASS | Russia | Uragan satellites; full global coverage restored in 2011 |
| Galileo | European Union | Civilian control; 30 satellites (24 operational, 6 spare) |
| BeiDou | China | Two constellations; first was BeiDou-1 |
| QZSS | Japan | Regional; nickname Michibiki ("guide"); the "Japanese GPS" |
| IRNSS | India | ISRO; up to 1,500 km beyond India; Standard Positioning Service and Restricted Service |
Applications of GNSS
- Consumer: receivers in smart phones show locations and routes.
- Transportation: tracking locomotives and rail cars; aircraft navigation.
- Port automation: tracking containers and steering cranes.
- Machine control: bulldozers, excavators, graders, pavers and farm machinery.
- Precision agriculture: farm planning, field mapping, soil sampling, tractor guidance, crop assessment.
- Surface mining: routing haul trucks to and from shovels.
- Survey: one surveyor can do in a day what a crew of three took a week to do.