Glossary A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A Absorption Reduction in the amount of light or radiation being transferred though a medium Absorption Coefficient Measurement of the amount of sunlight absorbed per metre depth of water Active Sensors Sensors with their own source of radiation, e.g. laser altimeters, imaging radar and acoustic systems Accuracy Is the degree of conformity of a measured or calculated quantity to its actual (true) value. Air-Water Interface Ocean-atmosphere (gas-liquid) boundary which alters the direction and magnitude of sunlight Airborne Laser ctive imaging system based on a green to red laser used to produce maps of land-surface height and bathymetry in shallow (< 20m) and clear waters. Airborne Radar Active imaging system using microwave energy to measure surface roughness and moisture content Ali Advanced Land Imager - next generation Landsat TM/ETM sensor on the EO-1 platform Algal Blooms A rapid and extensive growth of algae on the surface, water column or substrate Analytical Modeling mage processing approach used to estimate biophysical properties (e.g. total suspended sediment concentration) by applying radiative transfer equations to image data. AOP's Apparent optical properties of water - those dependent on the strength and direction of incident sunlight, e.g. reflectance. Atmospheric Correction mage processing approach used to remove scattering and absorption effects from image data so the signal used is that emanating fro the air-water interface or land surface, not the top of the atmosphere. Attenuation Distortion of true reflectance or radiance levels due to absorption and scattering effects. B Backscattering Coefficient A measure of the proportion of light at specific wavelengths that will be backscattered - dependent on particle size and form in water. Bathymetry Depth of the water column to substrate, measured relative to a specified height datum. Benthos Living organisms, organic and inorganic, commonly found on the seafloor Beam Attenuation Coefficient Measurement of the amount of absorption experienced by a collimated beam of light per metre depth of water. Biomass The amount of "living" material associated with a plant or organism. For plants biomass can be live and dead, and above or below ground. Bio-Optical Modeling Application of radiative transfer models to understand light interactions in aquatic media and use these to estimate water column constituents from image data. Biophysical Properties Biological and physical properties of an environment Boat Based Visual Assessments Assessments done from a boat where a video or still cameras is dropped in the water to visual assess an feature (e.g. benthos) real time via a monitor in the boat or via images later in the office. Return to top^ C Chlorophyll A Primary pigment used to capture sunlight for use in a plant's photosystem during photosynthesis. CASI Compact Airborne Spectrographic Imager - an airborne hyperspectral imaging system. Calibration A process used to initialize a mathematical model to certain measured conditions. CDOM Coloured dissolved organic material Coastal Environments Mangrove wetlands, inter-tidal and sub-tidal sections of a coastal embayment Coastal Indicators Selected biophysical parameters which have been recognised as being sensitive to the health or condition of coastal environments. Coastal-Marine Ecosystem Health Indicator See Coastal indicators Continuous Map A map showing spatial variation in a quantitative property, e.g. water depth, without grouping it into discrete thematic classes. Coordinate System A reference system used to define location in relation to a set origin point, i.e. [x, y, z] Coral Habitat An area with suitable conditions to allow the groath and maintenance of coral reefs. Cover Type A type of living or non-living feature, commonly occurring over substrate. Return to top^ D Datum An origin point or surface for vertical or horizontal coordinates Diffuse Skylight Sun-light that has been scattered by aerosol, dusts and clouds, and is not in a direct beam. Deep Benthic Cover Living and non-living features covering the substrate at depths greater than 15-20m Diving Visual Assessments where SCUBA diving gear is needed to visually assess the benthos or any other feature which is out of free diving range Down Welling Light moving downwards and away from the sun to the earth's surface Down Welling Irradiance Sunlight incident upon a surface from all viewing angles Return to top^ E Eo-1 NASA satellite - experimental platform for Hyperion and ALI Environmental Variable Bathymetry, benthic cover, water quality parameters are examples of variables which are describing the environment. Environmental Restrictions Environmental conditions in the atmosphere, se asurface and water column that affect the type and quality of remotely sensed information able to be collected, e.g. clouds, smoke, haze, wind, tidal currents, breaking waves, etc. Electro Magnetic Radiation (EMR) Energy emitted form any object with a temperature greater than absolute zero. This includes visible and non visible energy such as sunlight, infrared, thermal infrared and microwaves. EMR consists of units of energy (photons) which produce electric and magnetic field as they move through space. Different levels of EMR energy produce different types of light. Error Matrix A table for comparing the mapped value or category in an image to a reference value obtained from field survey. F Feasible Feasible applications are those that have been shown to work with experimental image data sets or over limited areas with very small pixels or global scales with large pixels. G Geometric Correction Or Georeferencing The process of converting an image into a forma where each pixel has a projection, datum and coordinate, enabling it to be integrated with other spatial data. Georeferencing See geometric correction Graphic Sequence One path for users to take through the toolkit where you can either select an environmental variable to map or explore the options for mapping from a specific sensor. Ground Resolution Element The smallest spatial sampling unit used by an imaging sensor to measure reflected or emitted EMR. The GRE is displayed as a pixel in an image. Ground Control Points Environmental features able to be seen on an image and on the ground/reef, where coordinates are obtained from field survey and are used to tie the image to ground coordinates. Return to top^ H Habitat The characteristic biotic and abiotic elements of an area, in which a specific organism lives, or as the characteristic of an area. Hydroscat-6 Instrument designed for measuring the backscattering coefficient of water bodies at a number different wavelengths. Hymap An airborne hyperspectral sensor with 126 bands from 400-2500nm collecting images from 3m - 10m pixels. www.hyvista.com Hyperion Experimental satellite-borne hyperspectral imaging systems with 30m pixels and 196 bands on the EO-1 platform. Hyperspectral A device is hyperspectral if it records reflected or emitted light using > 10, narrow spectral bandwidths (cf. multispectral) I Ikonos Commercially operated high spatial resolution (4m) multispectral and panchromatic (1m) satellite imaging sensor. Intertidal The region between spring high-water and low-water tidal limits which is exposed at low tide and inundated at high tide. Intertidal Benthic Cover Living and non-living features covering the inter-tidal substrate. Image Corrections Image processing operations designed to remove geometric and atmospheric distortions in an image data set. Image Pixel Smallest spatial sampling unit used by an imaging sensor to measure reflected or emitted energy from the surface of the earth. Inherent Optical Domain An area of water exhibiting similar absorption and scattering properties, hence similar water colours. Inherent Optical Properties Properties of the water column that do not change with illumination strength and direction, i.e. absorption and scattering coefficients. Irradiance Reflectance A ratio of reflected sunlight measured over all directions to incident sunlight measured over all directions. Return to top^ K Kd Vertical diffuse attenuation coefficient - an estimate of the amount of light attenuated by water per unit depth. L Landsat Thematic Mapper/Enhanced Thematic Mapper General purpose multispectral, moderate spatial resolution imaging satellite sensors that have operate since the mid 1980s (TM) and April 1999 (ETM). Level of Measurement Precision Required The smallest detectable level of change in the environmental being mapped. For example, do you need to map depth in 1cm or 1m increments? 1cm is a higher measurement precision. Level of Measurement Accuracy Required The smallest difference between estimated/mapped environmental variables and a reference value for that variable.For example, a comparison of a seagrass species map to field survey for a site may show an agreement or accuracy of 85% between image and field survey data. Return to top^ M Matrix Inversion Method A mathematical solution to the radiative transfer equation developed to enable its inversion to estimate concentrations of the water column constituents responsible for the water colour. Mapping Needs The information a manager, scientist, technician, student wants to produce from an image in a spatial form. The needs are the constraints to the project in terms of the area to cover, smallest feature to map, what is to be mapped and when to map it. MERIS Medium spectral resolution imaging spectrometer - See http://envisat.esa.int/object/index.cfm?fobjectid=1665 Minimum Mapping Unit The smallest spatial unit to be shown on a map MODIS Moderate Resolution Imaging Spectrometer - See http://modis.gsfc.nasa.gov/ Multi-Date Normalization An image correction approach used to remove the distorting effects of different types of atmospheric conditions over an image of the same area collected on different dates. Multi-Spectral An image data collection system where reflected or emitted energy is measured in less than 10 broad spectral bands. Multi-Temporal Data that has been collected for the same area over a series of successive dates. Return to top^ N Near Infra Red (Nir) The non-visible 700 -1000nm portion of the EMR spectrum Normalised Difference Vegetation Index A normalised ratio transformation using the red and NIR pixel values which is sensitive to vegetation cover. O Remote Sensing Reflectance Or R(0-) Atmospheric and air-water interface correction of image data produces this value in each pixel. This represents the ratio of upwelling radiance to downwelling irradiance just below the water surface. Objected Orientated Classification An approach to converting an image data to a map which works where the pixel size is significantly smaller than the target to be mapped. This approach identifies uniform spatial regions in an image which are then labeled by an analyst. Operational But Costly Operational applications are those that have been clearly demonstrated to work accurately from commercially available image data and standard image processing systems, and are delivering data at the required resolution. Optically Deep A water body where the bottom/substrate/benthos is not visible due to attenuation of incident sunlight. E.g. deep and clear water bodies or shallow and highly turbid water bodies. Optically Shallow A water body where the bottom/substrate/benthos is visible. Overall Accuracy A measure of agreement between an image based value and the value for the same location measured on the ground or from another data source. If both data sets agree the accuracy the accuracy is 100% Return to top^ P Panchromatic All visible wavelengths of light, i.e. a panchromatic image or photo is a black and white image of all visible bands. Passive Sensors Imaging sensors that measure reflected sunlight or emitted thermal energy. Per-pixel classification An approach to converting an image data to a map which works where the pixel is assumed to be made of one cover type. This approach assigns a cover type or class label to each pixel, so they are mapped individually. Platform Type The vehicle on which a sensor is mounted, e.g. satellite, aircraft, boat, balloon, person. Pixel Size The linear dimensions of a square in an image which contains the reflectance or emittance measured by a GRE PIFS Pseudo-Invariant Features - landscape features that retain the same reflectance over time and can be used for image calibration. Planimetric Projection A map projection where each map element is at its true location on the ground (cf. aerial photography and some satellite images which have a perspective projection). Precision The level of detail with which a measurement is made, e..g measuring depth in 1.0cm increments is more precise than measuring at 1.0m increments. Producer Accuracy A term used to define the level of agreement between an image based map of surface cover types and reference data for the same surface cover types. If 100 reference points are collected by the image processing technician (producer) and 80 of those are classified correctly, the producer's accuracy is 80%. Projection A set of equations for transforming a 3-dimensional surface to a planar 2-dimensional surface, i.e. for transforming 3-d earth measurements to a 2-d map. Positional Accuracy The difference between a measured coordinate and its true location or a reference value for that location. Return to top^ Q Quickbird Commercially operated high spatial resolution (2.68m) multispectral and panchromatic (0.7m) satellite imaging sensor. R Radiative Transfer Modeling Approach Application of equations that define the physics of how light moves through a medium and interacts with it. It is used to estimate the biophysical properties controlling reflection, absorption and transmission of light. Radiance A standard physical unit for measuring the amount of EMR incident on a unit area, over a unit time from a specific angle. Radiance units are watts/m2.sr, where watts = joules/seconds and sr = units of a solid 3-d angle, steradians. Radiometric Correction Conversion of image pixel digital numbers from a relative scale to an absolute physical units scale, e.g. radiance. Radiometric Resolution Smallest difference in reflected light able to be detected by a sensor and its dynamic range. Radio-Sonde Data Vertical profile through the atmosphere of temperature and humidity, used for atmospheric correction. Reflectance Signature Ratio of upwelling radiance to downwelling irradiance on a target, i.e. its characteristic absorption/reflectance response. Refraction Refraction is the change in direction of a wave due to a change in its speed. This is most commonly seen when a wave passes from one medium to another. Refraction of light is the most commonly seen example, but any type of wave can refract when it interacts with a medium, for example when sound waves pass from one medium into another. Return to top^ S Satellite Radar A side-looking imaging system that is active and is able to operate independent of sunlight. Scattering The process by which photons of light change the direction they are traveling due to a collision/interaction with a particle or molecule. Blue sky is produced by scattering of photons of blue light. Shallow Benthic Cover Living and non-living features covering the substrate at depths shallower than 15-20m Secchi Depth Commonly used approach to measure the clarity of a water body by dropping a black/white disk and noting the depth at which the black and white is no longer visible. Sensor Type Differences between imaging sensors are due to the type of sensor (passive or active), spatial resolution, spectral bands used and radiometric resolution. Side Scan Sonar A boat or UAV mounted active imaging system for mapping the seabed for a wide variety of purposes.In conjunction with seafloor samples it is able to provide an understanding of the differences in material and texture type of the seabed. Snorkelling Visual Survey Assessments where a snorkeler can visually assess the benthos or any other feature underwater which requires no SCUBA diving gear. Spatial Resolution A measure of the scale of the smallest feature able to be detected on an image. Spatial Dimensions The spatial attributes of an image or imaging sensor, referring to (1) the pixel size; and (2) the extent of the area covered by the image. Spectral Dimensions The type of reflected or emitted light recorded by a sensor, referring to (1) the position of spectral bands, e.g. blue, green, red; (2) width of spectral bands; and (3) number of spectral bands. Spectral Signature See reflectance signature Spectral Angle Mapping An image classification approach used to group pixels with similar reflectance signature. Spot Xs Commercially operated high-moderate spatial resolution (20m) multispectral and panchromatic (5m) satellite imaging sensor Striping Effects Artifacts introduced in coastal Landsat sensor scenes due to scanner variations every 16 lines. Submerged Aquatic Vegetation (SAV) Aquatic vegetation, such as sea grasses, that cannot withstand excessive drying and therefore live with their leaves at or below the water surface. Substrate Features See substrate types Substrate Types Types of material found on seafloor: sand, rock, seagrass, algae etc… Subsurface Irradiance Reflectance Similar quantity as R(0-), except this is measured as a ratio of upwelling to downwelling irradiance. Sun Glint Specular reflectance of sunlight from the water surface that makes it impossible to interpret or process water column and substrate/benthic cover information from the data. Supervised Classification Image processing approach used to group pixels with a similar spectral signature as these are assumed to be the same land-cover class. Suspended Sediment Sediment particles that are floating in suspension (as opposed to dissolved) in the water column. Return to top^ T Technical Officer The person who does all the real work Temporal Dimensions The time at which a sensor overflies a location to collect an image and/or repeat frequency of image acquisition. Thematic Map A map product derived by classifiying each image pixel into a single category or theme to represent a surface cover feature. Tripton The non-organic component or material found in the water column, i.e. total inorganic matter concentration. Total Suspended Inorganic Material (TSM) Tripton = TSM, is the non-organic fraction of the suspended load within the water column. U Underwater Acoustic An active sensor mounted on boats and used to map bathymetry. Underwater-Light-Climate A set of measurements defining the scattering and absorption controls in the water column. Upwelling Irradiance A measurement taken with the sensor head pointing down to capture incident direct and diffuse light over all directions. Unsupervised Classification A mapping approach used for per-pixel classification in image processing systems which groups pixels automatically based on their spectral reflectance signature. The analyst then labels the classes. User Accuracy A term used to define the level of accuracy of an image based map of surface cover types, where select locations are compared to reference data that the map user has. If 100 pixels are selected by the map user and compared to the actual ground cover class and 80 of those are classified correctly, the user's accuracy is 80%. Return to top^ V Validation The process used to compare image based estimates or map categories to some form of reference data to calculate their accuracy. W Water Clarity A subjective term used to verbally describe total attenuation of sunlight in a water column. This can also be represented by Secchi-depth and quantified as the diffuse attenuation coefficient. Water Roughness The state of the water surface which is a result of increased currents and wind. If no current and/or wind then water surface is flat and smooth. Wavelength The distance between peaks or troughs in the electric and magnetic field of EMR. It is sued to differentiate light with different energy levels, ie. high energy = short wavelength blue light and low energy = long wavelength IR lightt Water Quality Parameters Biological and physical properties of the water column that have been adopted by scientific and management agencies as indicative of the condition of a water body, e.g. Secchi depth, chlorophyll and total suspended sediment concentration. Return to top^
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