{"id":970,"date":"2012-03-26T19:47:44","date_gmt":"2012-03-27T00:47:44","guid":{"rendered":"http:\/\/tmackinnon.com\/?p=970"},"modified":"2019-01-10T13:15:32","modified_gmt":"2019-01-10T13:15:32","slug":"digital-elevation-models","status":"publish","type":"post","link":"https:\/\/tmackinnon.com\/digital-elevation-models.php","title":{"rendered":"Digital Elevation Models (DEMS)"},"content":{"rendered":"\n<style type=\"text\/css\" data-created_by=\"avia_inline_auto\" id=\"style-css-av-jpy10qwc-dfcf010f7cc70dfdf79a162a296ddaa9\">\n.avia-section.av-jpy10qwc-dfcf010f7cc70dfdf79a162a296ddaa9 .av-parallax .av-parallax-inner{\nbackground-repeat:no-repeat;\nbackground-image:url(https:\/\/tmackinnon.com\/wp-content\/uploads\/bouctouche.jpg);\nbackground-position:50% 100%;\nbackground-attachment:scroll;\n}\n.avia-section.av-jpy10qwc-dfcf010f7cc70dfdf79a162a296ddaa9 .av-section-color-overlay{\nopacity:0.7;\nbackground-color:#7d6f4f;\n}\n<\/style>\n<div id='av_section_1'  class='avia-section 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itemprop=\"headline\"  ><\/p>\n<p>Digital Elevation<br \/>\nModels (DEMS)<br \/>\n<\/h1><div class=\"special-heading-border\"><div class=\"special-heading-inner-border\"><\/div><\/div><\/div><\/div>\n<style type=\"text\/css\" data-created_by=\"avia_inline_auto\" id=\"style-css-av-3pci3-cad892e7f90b3a722543bccb76e2e1a7\">\n.flex_column.av-3pci3-cad892e7f90b3a722543bccb76e2e1a7{\nborder-radius:0px 0px 0px 0px;\npadding:0px 0px 0px 0px;\n}\n<\/style>\n<div  class='flex_column av-3pci3-cad892e7f90b3a722543bccb76e2e1a7 av_one_fifth  avia-builder-el-4  el_after_av_three_fifth  avia-builder-el-last  flex_column_div av-zero-column-padding  '     ><\/div>\n\n<\/div><\/div><\/main><!-- close content main element --><\/div><\/div><\/div><div class='clear'><\/div><div id='sub_menu1'  class='av-submenu-container av-qi0vu-ffedd9a33410f7020f845f6c16e0503a main_color  avia-builder-el-5  el_after_av_section  el_before_av_textblock  av-sticky-submenu submenu-not-first container_wrap sidebar_right' style='z-index:301' ><div class='container av-menu-mobile-disabled av-submenu-pos-center'><ul id=\"menu-mid-page-menu-1\" class=\"av-subnav-menu\" role=\"menu\"><li role=\"menuitem\" id=\"menu-item-47937\" class=\"menu-item menu-item-type-custom menu-item-object-custom menu-item-home menu-item-top-level menu-item-top-level-1\"><a href=\"https:\/\/tmackinnon.com\/\" itemprop=\"url\" tabindex=\"0\"><span class=\"avia-bullet\"><\/span><span class=\"avia-menu-text\">Home<\/span><span class=\"avia-menu-fx\"><span class=\"avia-arrow-wrap\"><span class=\"avia-arrow\"><\/span><\/span><\/span><\/a><\/li>\n<li role=\"menuitem\" id=\"menu-item-47792\" class=\"menu-item menu-item-type-post_type menu-item-object-page menu-item-top-level menu-item-top-level-2\"><a href=\"https:\/\/tmackinnon.com\/geographic-information-systems-gis\" itemprop=\"url\" tabindex=\"0\"><span class=\"avia-bullet\"><\/span><span class=\"avia-menu-text\">GIS<\/span><span class=\"avia-menu-fx\"><span 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menu-item-top-level menu-item-top-level-7\"><a href=\"https:\/\/canadiangis.com\/data.php\" itemprop=\"url\" tabindex=\"0\" rel=\"nofollow noopener\" target=\"_blank\"><span class=\"avia-bullet\"><\/span><span class=\"avia-menu-text\">Canadian Open Data<\/span><span class=\"avia-menu-fx\"><span class=\"avia-arrow-wrap\"><span class=\"avia-arrow\"><\/span><\/span><\/span><\/a><\/li>\n<\/ul><\/div><\/div><div class='sticky_placeholder'><\/div><div id='after_submenu_1'  class='main_color av_default_container_wrap container_wrap sidebar_right'  ><div class='container av-section-cont-open' ><div class='template-page content  av-content-small alpha units'><div class='post-entry post-entry-type-page post-entry-970'><div class='entry-content-wrapper clearfix'>\n<section  class='av_textblock_section av-jqqmsykj-cedb9c801983dddc725b999f4f6e4a36 '   itemscope=\"itemscope\" itemtype=\"https:\/\/schema.org\/BlogPosting\" itemprop=\"blogPost\" ><div class='avia_textblock'  itemprop=\"text\" ><p><img loading=\"lazy\" decoding=\"async\" class=\"alignright wp-image-971\" style=\"margin: 11px;\" title=\"Digital elevation model (DEM) of Lismore, Nova Scotia\" src=\"https:\/\/tmackinnon.com\/wp-content\/uploads\/lismore-dem1.jpg\" alt=\"Digital elevation model (DEM) of Lismore, Nova Scotia\" width=\"300\" height=\"300\" \/><\/p>\n<h2 align=\"justify\">Digital Elevation Models (DEMS)<\/h2>\n<p align=\"justify\">A digital elevation model (DEM) or sometimes referred to as a digital terrain model (DTM) is a quantitative representation of the topography of the Earth (or sometimes other surfaces) in a digital format. They are a common component of <a href=\"https:\/\/tmackinnon.com\/x\/gis\">geographic information systems<\/a> \/<a href=\"https:\/\/tmackinnon.com\/x\/rs\">remote sensing<\/a> and are usually represented by cartesian coordinates and numerical descriptions of altitude. In contrast with topographical vector maps, the information is stored in a raster format. That is, the map will normally divide the area into a rectangular grid of cells or pixels and store the elevation of each one as a DN value.<\/p>\n<p>Traditionally most common DEMs used in the Geomatics industry only contain elevation values of the true ground\u2019s surface but DEMs can also sometimes contain other features found upon the ground\u2019s surface as well. When it contains all features it is often referred to as a digital surface (DSM). Digital surface models contain elevation values representing the ground as well as any other objects such as buildings and trees.<\/p>\n<p>The resolution of the DEM, or the distance between adjacent grid points (often the size of the cell or pixel), is a critical parameter in determining the amount of detail that a user should except to represent in the DEM. The smaller the resolution, the more details or features that will be present, e.g. a 1 m resolution DEM will contain more details then a 20 m one and be better suited for hydrological analyses.<\/p>\n<p align=\"justify\">DEMs are used as a source of elevation (and to create other <a href=\"https:\/\/tmackinnon.com\/x\/rs\/digital-elevation-models\">digital terrain models<\/a>) for many different purposes such as:<\/p>\n<ul>\n<li>to orthorectify imagery<\/li>\n<li>as a source of topographic information and to create contour lines from<\/li>\n<li>to identify geological structures in topography<\/li>\n<li>to identify risk areas and hydrological flow patterns<\/li>\n<li>to <a href=\"https:\/\/tmackinnon.com\/3d-flood-modeling-with-high-resolution-lidar.php\">identify flood risk<\/a> areas<\/li>\n<li>to determine accessibility<\/li>\n<li>to identify regions of visibility for radio or cell towers<\/li>\n<li>to predict how the terrain can effect signal strength and reflection<\/li>\n<li>and many more uses<\/li>\n<\/ul>\n<p align=\"justify\">Digital elevation models may be prepared in a number of ways, but they are frequently obtained by remote sensing rather than direct survey. Older methods of generating DEMs often involved interpolating digital contour maps from aerial photography produced by direct survey and interpretation of the surface.<\/p>\n<p>Many mapping agencies produce their own DEMs, often of a higher resolution and quality, but frequently these have to be purchased, sometimes at considerable cost. The two methods of creating DEMs that are covered on this web site deal with LIDAR and Photogrammetry methods.<\/p>\n<ul>\n<li>MacKinnon E (2003) <a href=\"https:\/\/tmackinnon.com\/2005\/rs\/lidar\/LIDAR-DEM-Modeling.pdf\" target=\"_blank\" rel=\"noopener\">Surface Modeling and LIDAR Validation<\/a> Middleton, Nova Scotia: Applied Geomatics Research Group, Centre of Geographic Sciences, 49 pages<\/li>\n<li>MacKinnon E, Sangster F &amp; Hynes D (1999) <a href=\"https:\/\/tmackinnon.com\/2005\/rs\/3d_modeling\/Labrador_presentation.pdf\" target=\"_blank\" rel=\"noopener\">Makkovik, Labrador &#8211; 3D modeling and Data Integration<\/a> presented at the Bedford Institute of Oceanography in Dartmouth, Nova Scotia<\/li>\n<\/ul>\n<\/div><\/section>\n<section  class='av_textblock_section av-8kn36-67fef207cd59dae3b3c32b23f20a7864 '   itemscope=\"itemscope\" itemtype=\"https:\/\/schema.org\/BlogPosting\" itemprop=\"blogPost\" ><div class='avia_textblock'  itemprop=\"text\" ><div align=\"center\"><script async src=\"\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js\"><\/script><br \/>\n<!-- tmackinnon-links --><br \/>\n<ins class=\"adsbygoogle\" style=\"display: block;\" data-ad-client=\"ca-pub-4620870266094734\" data-ad-slot=\"4956701146\" data-ad-format=\"link\"><\/ins><br \/>\n<script>\n(adsbygoogle = window.adsbygoogle || []).push({});\n<\/script><\/div>\n<\/div><\/section>\n<div  class='av-social-sharing-box av-4oh22v-a107746cbdd13688d845e9e41d6dc253 av-social-sharing-box-minimal  avia-builder-el-8  el_after_av_textblock  avia-builder-el-last  av-social-sharing-box-fullwidth'><div class=\"av-share-box\"><h5 class='av-share-link-description av-no-toc '>Share this entry<\/h5><ul class=\"av-share-box-list noLightbox\"><li class='av-share-link av-social-link-facebook avia_social_iconfont' ><a target=\"_blank\" aria-label=\"Share on Facebook\" href=\"https:\/\/www.facebook.com\/sharer.php?u=https:\/\/tmackinnon.com\/digital-elevation-models.php&#038;t=Digital%20Elevation%20Models%20%28DEMS%29\" data-av_icon=\"\ue8f3\" data-av_iconfont=\"entypo-fontello\" title=\"\" data-avia-related-tooltip=\"Share on Facebook\"><span class='avia_hidden_link_text'>Share on Facebook<\/span><\/a><\/li><li class='av-share-link av-social-link-twitter avia_social_iconfont' ><a target=\"_blank\" aria-label=\"Share on X\" href=\"https:\/\/twitter.com\/share?text=Digital%20Elevation%20Models%20%28DEMS%29&#038;url=https:\/\/tmackinnon.com\/?p=970\" data-av_icon=\"\ue932\" data-av_iconfont=\"entypo-fontello\" title=\"\" data-avia-related-tooltip=\"Share on X\"><span class='avia_hidden_link_text'>Share on X<\/span><\/a><\/li><li class='av-share-link av-social-link-pinterest avia_social_iconfont' ><a target=\"_blank\" aria-label=\"Share on Pinterest\" href=\"https:\/\/pinterest.com\/pin\/create\/button\/?url=https%3A%2F%2Ftmackinnon.com%2Fdigital-elevation-models.php&#038;description=Digital%20Elevation%20Models%20%28DEMS%29&#038;media=https%3A%2F%2Ftmackinnon.com%2Fwp-content%2Fuploads%2Flismore-dem1.jpg\" data-av_icon=\"\ue8f8\" data-av_iconfont=\"entypo-fontello\" title=\"\" data-avia-related-tooltip=\"Share on Pinterest\"><span class='avia_hidden_link_text'>Share on Pinterest<\/span><\/a><\/li><li class='av-share-link av-social-link-linkedin avia_social_iconfont' ><a target=\"_blank\" aria-label=\"Share on LinkedIn\" href=\"https:\/\/linkedin.com\/shareArticle?mini=true&#038;title=Digital%20Elevation%20Models%20%28DEMS%29&#038;url=https:\/\/tmackinnon.com\/digital-elevation-models.php\" data-av_icon=\"\ue8fc\" data-av_iconfont=\"entypo-fontello\" title=\"\" data-avia-related-tooltip=\"Share on LinkedIn\"><span class='avia_hidden_link_text'>Share on LinkedIn<\/span><\/a><\/li><li class='av-share-link av-social-link-reddit avia_social_iconfont' ><a target=\"_blank\" aria-label=\"Share on Reddit\" href=\"https:\/\/reddit.com\/submit?url=https:\/\/tmackinnon.com\/digital-elevation-models.php&#038;title=Digital%20Elevation%20Models%20%28DEMS%29\" data-av_icon=\"\ue927\" data-av_iconfont=\"entypo-fontello\" title=\"\" data-avia-related-tooltip=\"Share on Reddit\"><span class='avia_hidden_link_text'>Share on Reddit<\/span><\/a><\/li><li class='av-share-link av-social-link-mail avia_social_iconfont' ><a  aria-label=\"Share by Mail\" href='mailto:?subject=Digital%20Elevation%20Models%20%28DEMS%29&#038;body=https:\/\/tmackinnon.com\/digital-elevation-models.php' data-av_icon='\ue805' data-av_iconfont='entypo-fontello'  title='' data-avia-related-tooltip='Share by Mail'><span class='avia_hidden_link_text'>Share by Mail<\/span><\/a><\/li><\/ul><\/div><\/div>\n","protected":false},"excerpt":{"rendered":"<p>A digital elevation model (DEM) or sometimes referred to as a digital terrain model (DTM) is a quantitative representation of the topography of the Earth. DEMs are used as a source of elevation (and to create other digital terrain models) for many different purposes <\/p>\n","protected":false},"author":1,"featured_media":971,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[172,173],"tags":[363,136,357,356,354,360,669,361,362,359,661,353,355,352,358],"class_list":["post-970","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-digital-elevation-models","category-terrain-analysis","tag-contour-lines","tag-dem","tag-digital-elevation-model","tag-digital-terrain-model","tag-dtm","tag-geomatics-industry","tag-gis","tag-grid","tag-imagery","tag-information","tag-lidar","tag-raster","tag-resolution","tag-vector","tag-vector-maps"],"_links":{"self":[{"href":"https:\/\/tmackinnon.com\/wp-json\/wp\/v2\/posts\/970","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/tmackinnon.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/tmackinnon.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/tmackinnon.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/tmackinnon.com\/wp-json\/wp\/v2\/comments?post=970"}],"version-history":[{"count":0,"href":"https:\/\/tmackinnon.com\/wp-json\/wp\/v2\/posts\/970\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/tmackinnon.com\/wp-json\/wp\/v2\/media\/971"}],"wp:attachment":[{"href":"https:\/\/tmackinnon.com\/wp-json\/wp\/v2\/media?parent=970"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/tmackinnon.com\/wp-json\/wp\/v2\/categories?post=970"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/tmackinnon.com\/wp-json\/wp\/v2\/tags?post=970"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}