{"id":61,"date":"2016-08-01T15:06:09","date_gmt":"2016-08-01T14:06:09","guid":{"rendered":"http:\/\/generic.wordpress.soton.ac.uk\/rs4eo\/?page_id=61"},"modified":"2020-09-24T15:54:49","modified_gmt":"2020-09-24T14:54:49","slug":"2-2-radiation-and-remote-sensing","status":"publish","type":"page","link":"https:\/\/generic.wordpress.soton.ac.uk\/rs4eo\/2-electromagnetic-radiation-and-electromagnetic-spectrum\/2-2-radiation-and-remote-sensing\/","title":{"rendered":"2.2. Radiation and Remote Sensing"},"content":{"rendered":"<p><strong>Sources<\/strong><\/p>\n<p>There are four main affects to the signal in a remote sensing system:<\/p>\n<ol>\n<li>The source of radiation<\/li>\n<li>Atmospheric effects<\/li>\n<li>Interaction with the target<\/li>\n<li>Sensor<\/li>\n<\/ol>\n<p>There are three main sources of radiation as can be seen in the diagram:<\/p>\n<ol>\n<li>The sun (passive systems)<\/li>\n<li>The target itself (also a passive system)<\/li>\n<li>A source on the remote sensing platform (active system)<\/li>\n<\/ol>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/generic.wordpress.soton.ac.uk\/rs4eo\/wp-content\/uploads\/sites\/106\/2016\/08\/2.9.gif\" class=\"alignnone wp-image-74 size-full\" height=\"269\" width=\"408\" \/><\/p>\n<hr \/>\n<p><strong>Reflection<\/strong><\/p>\n<div id=\"ta45_8\" class=\"block\">\n<p>Link the following systems into the classes of radiation source above:<\/p>\n<ul>\n<li>Light emissions of a volcano at night measured from a satellite<\/li>\n<li>Ultraviolet radiation measured over a land surface in the day<\/li>\n<li>Radar measurements taken from the space shuttle<\/li>\n<\/ul>\n<p>\r\n<script>\/\/ <![CDATA[\r\nfunction showFunct() { document.getElementById(\"hideshow\").style.display = \"block\"; } function hideFunct() { document.getElementById(\"hideshow\").style.display = \"none\"; }\r\n\/\/ ]]><\/script>\r\n<\/p>\r\n<p style=\"text-decoration: underline; color: #336699;\" onclick=\"showFunct()\">Show Answer<\/p>\r\n<div id=\"hideshow\" style=\"display: none;\">\r\n<p>The volcano at night is passive type (2), as the volcano itself is glowing, not reflected sunlight. Ultraviolet in the day is measuring reflected light from the sun making it type (1). Commonly radar is an active system: type 3.<\/p>\r\n<p style=\"text-decoration: underline; color: #336699; text-align: right;\" button=\"\" onclick=\"hideFunct()\">Hide Answer<\/p>\r\n<\/div>\n<hr \/>\n<p><strong>Electromagnetic Radiation<\/strong><\/p>\n<p>The electomagnetic radiation spectrum varies by wavelength as explained in this animation<\/p>\n<p><em>N\/B: The animation below will not show on the webpage, but you can save\/keep them on your computer and view them using the Adobe Flash Player 32 you downloaded earlier<\/em><\/p>\n<\/div>\n<iframe loading=\"lazy\" src=\"http:\/\/www.edshare.soton.ac.uk\/id\/document\/291423\" width=\"640\" height=\"480\"><\/iframe>\n<p><b>Infrared and Visible Light<\/b><\/p>\n<p>The reason our eyes see in three bands of visible light is that this is wavelength that the sun emits most energy in.\u00a0 Consequently, near infra red light emitted by the sun is powerful when compared to the energy the sun emits in the far infra red (far infra red is a longer wavelength) as the energy emitted begins to drop off.<\/p>\n<p>An iron put in the fire glows with a red colour, if it is taken out of the fire it glows duller red and finally appears to emit no light at all.\u00a0 However, it is emitting still but as infra red radiation.\u00a0 The general rule is that the cooler the object, the longer the wavelength of light.<\/p>\n<hr \/>\n<p><strong>Reflection<\/strong><\/p>\n<p>Which of the two radiation types near infrared and far infrared do you think is associated with passive measurements of temperature at night and which is associated with measuring reflected light from the sun?<\/p>\n<p>\r\n<script>\/\/ <![CDATA[\r\nfunction showFunct2() { document.getElementById(\"hideshow2\").style.display = \"block\"; } function hideFunct2() { document.getElementById(\"hideshow2\").style.display = \"none\"; }\r\n\/\/ ]]><\/script>\r\n<\/p>\r\n<p style=\"text-decoration: underline; color: #336699;\" onclick=\"showFunct2()\">Show Answer<\/p>\r\n<div id=\"hideshow2\" style=\"display: none;\">\r\n<p>NIR is far more abundant in sunlight than far infrared so this is wavelength commonly used in day time measurement of reflected sunlight.   Far infrared is the wavelength that cool night time objects emit light in so this is the wavelength commonly used for passive measurements of temperature at night.<\/p>\r\n<p style=\"text-decoration: underline; color: #336699; text-align: right;\" button=\"\" onclick=\"hideFunct2()\">Hide Answer<\/p>\r\n<\/div>\n<hr \/>\n<p><strong>Microwaves<\/strong><\/p>\n<p>Microwave remote sensing can be active as with radar but can also be a passive system.\u00a0 One of its main advantages is that it is unaffected by clouds unlike visible light.\u00a0 Rainfall measurements shown on weather forecasts are often radar measurements of rainfall.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Sources There are four main affects to the signal in a remote sensing system: The source of radiation Atmospheric effects Interaction with the target Sensor There are three main sources of radiation as can be seen in the diagram: The sun (passive systems) The target itself (also a passive system) A source on the remote [&hellip;]<\/p>\n","protected":false},"author":1726,"featured_media":0,"parent":35,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-61","page","type-page","status-publish","hentry"],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/generic.wordpress.soton.ac.uk\/rs4eo\/wp-json\/wp\/v2\/pages\/61","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/generic.wordpress.soton.ac.uk\/rs4eo\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/generic.wordpress.soton.ac.uk\/rs4eo\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/generic.wordpress.soton.ac.uk\/rs4eo\/wp-json\/wp\/v2\/users\/1726"}],"replies":[{"embeddable":true,"href":"https:\/\/generic.wordpress.soton.ac.uk\/rs4eo\/wp-json\/wp\/v2\/comments?post=61"}],"version-history":[{"count":13,"href":"https:\/\/generic.wordpress.soton.ac.uk\/rs4eo\/wp-json\/wp\/v2\/pages\/61\/revisions"}],"predecessor-version":[{"id":901,"href":"https:\/\/generic.wordpress.soton.ac.uk\/rs4eo\/wp-json\/wp\/v2\/pages\/61\/revisions\/901"}],"up":[{"embeddable":true,"href":"https:\/\/generic.wordpress.soton.ac.uk\/rs4eo\/wp-json\/wp\/v2\/pages\/35"}],"wp:attachment":[{"href":"https:\/\/generic.wordpress.soton.ac.uk\/rs4eo\/wp-json\/wp\/v2\/media?parent=61"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}