The marine environment is unique and requires technologies that can use sound to gather information since there is little light underwater. The seafloor is characterized using underwater sound and acoustical systems. Current technological innovations are allowing scientists to further understand and apply information about animal locations and habitat. Remote sensing and exploration with underwater vehicles allows scientists to map and understand the sea floor, and in some cases, the water column. In this lesson, the students will be shown benthic habitat images produced by GIS. These imaged will lead to a class discussion on why habitat mapping is useful and how current technology works to make bathymetry mapping possible. The teacher will then ask inquiry-based questions to have students brainstorm about the importance of bathymetry mapping.

Students will learn how remote sensing and underwater vehicles designed and built by engineers are improving the ability of scientists to map marine habitats. Habitat Bathymetry Soundings Remote Sensing Sonar GIS Map Ability to use data to create a simple line graph Ability to measure accurately in inches Students will be able to explain current technologies employed in mapping resources. Students will be able to draw conclusions from a set of collected data. Research in marine science is more complex than terrestrial research. Limitations of humans to explore underwater have traditionally made it difficult to study animals, habitats, and their interactions. Current technological innovations are allowing scientists to further understand and apply information about animal locations and habitat. Remote sensing and exploration with underwater vehicles allows scientists to map and understand the sea floor, and in some cases, the water column. Geographic Information Systems (GIS) allows for management and viewing of spatial relationships/mapping. In this lesson, the teacher should show GIS images of the ocean bathymetry and possibly GIS-animated clips, or flythroughs, to engage and familiarize the students to the subject. The students will learn how GIS works as well as the importance and application of habitat mapping. Concepts Many technologies are used to study seafloor geology and habitats. Information provided by these technologies helps scientists understand seafloor topography, the geological processes that shape Earth, and habitats that support marine organisms. Understanding the shape of the seafloor is crucial to advancing our knowledge of the ocean. The marine environment is unique and requires technologies that can use sound to gather information since there is little light underwater. The seafloor is characterized using underwater sound and acoustical systems. These advanced systems are usually mounted or towed behind large survey vessels. Bathymetric Data Bathymetry surveys and is a common methods used to characterize the seafloor. Bathymetry refers to water depth in relation to sea level. Echosounders are used to determine the ocean's depths, or bathymetric data. The echosounder emits sound into the ocean. The sound travels from the vessel to the seafloor and is reflected back to the vessel. The sound is received and recorded. Seafloor depth is calculated using the travel time of sound and the speed of sound in water. The equation used to determine depth: Distance = speed x (time/2). Echosounders can release multiple sound beams at one time, multibeam, which provide depths for a swath of the ocean's bottom. This technique allows lots of information to be gathered at one time. This data allows oceanographers to make maps of the seafloor. Data gathered also helps to identify bottom features such as ridges and shipwrecks as well as provide important information to boat captains and fishermen. Side Scan Sonar Side scan sonar also uses sound to interpret the topography and bathymetry of the seafloor. The side scan sonar instrument known as the 'fish' releases a sound. The sound is reflected from the seafloor and returns to the fish. The multibeam echosounder uses time to calculate depth. Side scan sonar uses the strength of the returning sound, or acoustical signal, to create an image of the seafloor. The strength of the acoustical signal depends on the shape and texture of the seafloor. A hard rock will return a stronger acoustical signal than soft sand. The strength of the signal transmits a light or dark shade onto an image. These images allow oceanographers to interpret underground structures such as volcanoes, canyons, and seamounts. Remote Sensing Remote = distance, away from source. Sensing = the process of sensing data and sending the data to a processor, which records the data and interprets the information. What do you need for remote sensing? Sensor Processor Radiation, light, sound… something to measure What do we use to measure? Cameras Lasers Radio frequency receivers Radar systems Sonar The below example of remote sensing was excerpted from, "How does satellite remote sensing work?" an article by the Food and Agriculture Organization of the United Nations: "On board Landsat 5 is a sensor called a thematic mapper. The Earth's rotation below the satellite allows this sensor to scan a new area of the planet's surface with each consecutive pass. The width of the area scanned, called the swath, is 185 km. A full scene is defined as 185 km x 185 km, an area of approximately 34 000 km2, or roughly twice the size of Kuwait. The thematic mapper detects the solar energy reflected off the earth's features as well as the Earth's own thermal energy on seven well-defined portions (bands) of the electromagnetic spectrum. For the bands sensing reflected light, the sensor can distinguish spatial features at a resolution of 30 m; meaning features 30 m in size are identifiable. The thematic mapper's thermal channel, however, identifies features at the much lower resolution of 120 m. The energy detected by the sensor is recorded electronically, not on photographic film. The images produced by remote sensing are not photographs. Because various features on the Earth's surface interact with and reflect solar energy differently in the various bands, the thematic mapper can be used to identify clearly a broad range of elements of land cover. For example, healthy green leaves are excellent reflectors of near-infrared wavelengths. The thematic mapper's fourth band detects reflected energy in this range, so it is particularly useful for identifying and mapping vegetation in a given area. Data from the thematic mapper are transmitted to stations on the ground. By international agreements, this information must be made available to anyone who requests it." Exploring the Ocean Floor with Satellite Altimeter Data: Geosat satellite was launched by the US Navy in 1985 and orbits the earth 14.3 times per day. Tiny bumps and dips in the ocean basin can be measured using a very accurate radar mounted on a satellite. The satellite-derived measurements can be compared and combined with measurements made by ships. Confirmation of the theory of plate tectonics. Spreading ridges are characterized by a pattern of ridges and transform faults. Calilbration by depth soundings. Other application of remote sensing: People other than oceanographers find Sea Surface Temperature maps useful. Swimmers can use these maps to decide which beach has water temperature that is "just right." The food that fish feed on tends to get trapped where warm and cold water meet, so fisherman use the SST images to determine where to drop their nets. The US Coast Guard uses these maps for search and rescue operations to help them determine how cold the water is where someone is missing so they know how long someone can survive before they succumb to hypothermia. What else is bathymetry used for? Currents Tides Mixing & upwelling Seamounts The process of detecting and monitoring physical characteristics of an area by measuring its reflected and emitted radiation and without physically contacting the object. The area or environment where an organism or ecological community normally lives or occurs. Where an object or animal is located in space. The angular distance north or south of the earth's equator, measured in degrees along a meridian, as on a map or globe. Angular distance on the earth's surface, measured east or west from the prime meridian at Greenwich, England, to the meridian passing through a position, expressed in degrees (or hours), minutes, and seconds. Technique of sending a sound via an instrument in which the sound is reflected from a target object. The return time is used to calculate depth or distance to the target. Technique of sending a sound wave through a space and recording how long it takes for the sound to bounce off as object and return again; used to determine distances or depths. Measuring water depth using a weighted rope. The measurement of the depth of bodies of water. A manufactured object or vehicle intended to orbit the earth, the moon, or another celestial body. Map that Habitat Engage students in a discussion regarding knowledge of oceanographic data collection, bathymetry, and mapping. The instructor should be sure to ask inquiry/open-ended questions about not only how we do this, but why? Did the students gain an understanding of the importance of remote sensing technologies and mapping? www.ngdc.noaa.gov/mgg/image/triple.gif www.usgs.gov This link provides more information on remote sensing using satellites. http://www.coolclassroom.org/whats_cool/remotesensingsat.html There are Masters degree programs in remote sensing. This is a sign of the importance of this growing field. The following link provides more information. http://www.soes.soton.ac.uk/MSc/ORS/ Satellite altimeter data & use Satellite altimeter data & use, http://www.ngdc.noaa.gov/mgg/bathymetry/predicted/explore.HTML#sat_alt , 07/09/04. Satellite altimeter data & use Swath bathymetry & side scan sonar Swath bathymetry & side scan sonar, http://woodshole.er.usgs.gov/operations/sfmapping/swath.htm, 07/09/04. Swath bathymetry & side scan sonar from USGS