{"id":187771,"date":"2008-09-26T21:39:09","date_gmt":"2008-09-27T04:39:09","guid":{"rendered":"http:\/\/www.esri.com\/arcgis-blog\/?post_type=blog&p=187771"},"modified":"2018-12-18T11:59:26","modified_gmt":"2018-12-18T19:59:26","slug":"some-best-practices-for-working-with-dems","status":"publish","type":"blog","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems","title":{"rendered":"Some best practices for working with DEMs"},"author":4351,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","format":"standard","meta":{"_acf_changed":false,"_searchwp_excluded":""},"categories":[22941],"tags":[38211,24131,24141,23211],"industry":[],"product":[36991],"class_list":["post-187771","blog","type-blog","status-publish","format-standard","hentry","category-mapping","tag-arcgis-methods","tag-dem","tag-elevation","tag-map-data","product-arcgis-desktop"],"acf":{"short_description":"\r\n\r\nMost of us use digital elevation models (DEMs) which are raster data sets that represent a continuous elevation surface in which each cell","flexible_content":[{"acf_fc_layout":"content","content":"

\"\"<\/p>\n

Most of us use digital elevation models (DEMs) which are raster data sets that represent a continuous elevation surface in which each cell represents the elevation at its location. DEM data are typically available in tiles that are sized to balance ease of data sharing with coverage so that those who need several tiles to cover their area of interest are not overburdened with extensive post-download data processing.<\/p>\n

<\/span>We are frequently asked a variety of questions about managing DEM datasets and how to derive other datasets like hillshade or slope. Here are some of the best practices that have come from these discussions and our thoughts on them:<\/p>\n

Manage DEMs in their native geographic coordinate system as opposed to a projected coordinate system<\/strong><\/p>\n

Always strive to obtain and maintain a \u201cgold\u201d copy or master of the DEM dataset \u2014 this is the data in the geographic coordinate system, for example, WGS84 or NAD83, that was used when the data were originally collected. In terms of data fidelity, this is the most accurate representation of the elevation model you have because it will not have undergone transformations, like projection, which can degrade the data for further display or analysis.<\/p>\n

Naming DEMs and derived datasets<\/strong><\/p>\n

I include either \u201c_ft\u201d or \u201c_m\u201d at the end of my DEM\u2019s name to indicate the units of elevation. I do the same for contours that I derive from my DEMs. This is important to know because if the elevation units are different from the linear (x,y) units, you will likely have to use the z factor to make sure your derived rasters (hillshade, slope, etc.) are correct \u2014 see the blog entry \u201cSetting the Z Factor Parameter Correctly<\/a>\u201d for more on this.<\/p>\n

I use \u201c_per\u201d or \u201c_deg\u201d for my slope output to indicate whether the slope is expressed in degrees or as a percentage.<\/p>\n

Avoid projecting DEMs that already use a projected coordinate system<\/strong><\/p>\n

When a\u00a0raster dataset is projected<\/a>,it is distorted, sometimes greatly, and if the original dataset is deleted, some data are lost. For example, for a raster DEM that has been projected into UTM Zone 11 North, each of the northern-most cells contain elevation values that are a result of averaging\/sampling a run of several cells from a row in the original dataset. If you were to project that dataset into a geographic coordinate system, the run of cells representing one northern edge UTM cell would be stretched into an evenly averaged range of elevation values.<\/p>\n

In other words, it is only possible to maintain fidelity in the DEM data when the data are projected from a geographic to a projected coordinate system. An equivalent of the original data can never be obtained by additional projecting the data back \u2013 some of the accuracy in the measurement will always be lost.<\/p>\n

Mosaic DEM tiles first before projecting or producing derivative datasets<\/strong><\/p>\n

If your area of interest covers more than one DEM tile, use the\u00a0Mosaic tool<\/a>\u00a0to combine the tiles first before producing other datasets and projecting them, otherwise you will introduce error into the derived datasets. If you want to test this, try first projecting a DEM dataset and then producing a hillshade \u2013 you\u2019ll typically see stripes in the resulting hillshade. On the other hand, if you first produce the hillshade from the original unprojected DEM and then project the hillshade, the result will look right. The same goes for all other derived products including slope and aspect datasets and more complex products, like watersheds or flow analyses that are the result of some fo the hydrographic analysis tools.<\/p>\n

Publishing and sharing DEM datasets<\/strong><\/p>\n

Last, if you are a producer\/publisher of DEM rasters for your area, please do not publish\u00a0only\u00a0<\/strong><\/em>a projected edition of your data. Doing so severely limits what your customers can do with your data. First and foremost, publish your DEM data in the original geographic coordinate system so that is appropriate for general use. Then, if there is a standard projected coordinate system in use for your area, and you want to save your customers some time, additionally publish derived products like combined DEM tiles, hillshades, slope datasets, and so on, that you have created by first generating the derived raster data\u00a0THEN\u00a0<\/strong>projecting it.<\/p>\n"}],"authors":[{"ID":4351,"user_firstname":"Charlie","user_lastname":"Frye","nickname":"Charlie Frye","user_nicename":"cfrye","display_name":"Charlie Frye","user_email":"cfrye@esri.com","user_url":"","user_registered":"2018-03-02 00:15:58","user_description":"I am the Chief Cartographer at Esri and work on the Living Atlas Team. I have been with Esri in Software Products since 1994. I specialize in GIS engineering and information product design. I am the author of many global scientific and thematic layers on topics that include ecosystems, landforms, population, climate, emissions, etc. Contact me at cfrye@esri.com with questions or feedback.","user_avatar":""}],"related_articles":"","card_image":false,"wide_image":false},"yoast_head":"\nSome best practices for working with DEMs<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Some best practices for working with DEMs\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems\" \/>\n<meta property=\"og:site_name\" content=\"ArcGIS Blog\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/esrigis\/\" \/>\n<meta property=\"article:modified_time\" content=\"2018-12-18T19:59:26+00:00\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:site\" content=\"@ESRI\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":[\"Article\",\"BlogPosting\"],\"@id\":\"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems#article\",\"isPartOf\":{\"@id\":\"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems\"},\"author\":{\"name\":\"Charlie Frye\",\"@id\":\"https:\/\/www.esri.com\/arcgis-blog\/#\/schema\/person\/cb24d44b9b7464f8eafd9fde29ae5c7a\"},\"headline\":\"Some best practices for working with DEMs\",\"datePublished\":\"2008-09-27T04:39:09+00:00\",\"dateModified\":\"2018-12-18T19:59:26+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems\"},\"wordCount\":7,\"publisher\":{\"@id\":\"https:\/\/www.esri.com\/arcgis-blog\/#organization\"},\"keywords\":[\"ArcGIS Methods\",\"digital elevation model (DEM)\",\"elevation\",\"Map Data\"],\"articleSection\":[\"Mapping\"],\"inLanguage\":\"en-US\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems\",\"url\":\"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems\",\"name\":\"Some best practices for working with DEMs\",\"isPartOf\":{\"@id\":\"https:\/\/www.esri.com\/arcgis-blog\/#website\"},\"datePublished\":\"2008-09-27T04:39:09+00:00\",\"dateModified\":\"2018-12-18T19:59:26+00:00\",\"breadcrumb\":{\"@id\":\"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/www.esri.com\/arcgis-blog\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Some best practices for working with DEMs\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/www.esri.com\/arcgis-blog\/#website\",\"url\":\"https:\/\/www.esri.com\/arcgis-blog\/\",\"name\":\"ArcGIS Blog\",\"description\":\"Get insider info from Esri product teams\",\"publisher\":{\"@id\":\"https:\/\/www.esri.com\/arcgis-blog\/#organization\"},\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/www.esri.com\/arcgis-blog\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-US\"},{\"@type\":\"Organization\",\"@id\":\"https:\/\/www.esri.com\/arcgis-blog\/#organization\",\"name\":\"Esri\",\"url\":\"https:\/\/www.esri.com\/arcgis-blog\/\",\"logo\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/www.esri.com\/arcgis-blog\/#\/schema\/logo\/image\/\",\"url\":\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/04\/Esri.png\",\"contentUrl\":\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/04\/Esri.png\",\"width\":400,\"height\":400,\"caption\":\"Esri\"},\"image\":{\"@id\":\"https:\/\/www.esri.com\/arcgis-blog\/#\/schema\/logo\/image\/\"},\"sameAs\":[\"https:\/\/www.facebook.com\/esrigis\/\",\"https:\/\/x.com\/ESRI\",\"https:\/\/www.linkedin.com\/company\/5311\/\"]},{\"@type\":\"Person\",\"@id\":\"https:\/\/www.esri.com\/arcgis-blog\/#\/schema\/person\/cb24d44b9b7464f8eafd9fde29ae5c7a\",\"name\":\"Charlie Frye\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/www.esri.com\/arcgis-blog\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/04\/CF_R3.png\",\"contentUrl\":\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/04\/CF_R3.png\",\"caption\":\"Charlie Frye\"},\"description\":\"I am the Chief Cartographer at Esri and work on the Living Atlas Team. I have been with Esri in Software Products since 1994. I specialize in GIS engineering and information product design. I am the author of many global scientific and thematic layers on topics that include ecosystems, landforms, population, climate, emissions, etc. Contact me at cfrye@esri.com with questions or feedback.\",\"knowsAbout\":[\"ArcGIS\"],\"knowsLanguage\":[\"English\"],\"jobTitle\":\"Distinguished GIS Engineer and Chief Cartographer\",\"worksFor\":\"Environmental Systems Research Institute, Inc.\",\"url\":\"https:\/\/www.esri.com\/arcgis-blog\/author\/cfrye\"}]}<\/script>\n<!-- \/ Yoast SEO Premium plugin. -->","yoast_head_json":{"title":"Some best practices for working with DEMs","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems","og_locale":"en_US","og_type":"article","og_title":"Some best practices for working with DEMs","og_url":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems","og_site_name":"ArcGIS Blog","article_publisher":"https:\/\/www.facebook.com\/esrigis\/","article_modified_time":"2018-12-18T19:59:26+00:00","twitter_card":"summary_large_image","twitter_site":"@ESRI","schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":["Article","BlogPosting"],"@id":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems#article","isPartOf":{"@id":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems"},"author":{"name":"Charlie Frye","@id":"https:\/\/www.esri.com\/arcgis-blog\/#\/schema\/person\/cb24d44b9b7464f8eafd9fde29ae5c7a"},"headline":"Some best practices for working with DEMs","datePublished":"2008-09-27T04:39:09+00:00","dateModified":"2018-12-18T19:59:26+00:00","mainEntityOfPage":{"@id":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems"},"wordCount":7,"publisher":{"@id":"https:\/\/www.esri.com\/arcgis-blog\/#organization"},"keywords":["ArcGIS Methods","digital elevation model (DEM)","elevation","Map Data"],"articleSection":["Mapping"],"inLanguage":"en-US"},{"@type":"WebPage","@id":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems","url":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems","name":"Some best practices for working with DEMs","isPartOf":{"@id":"https:\/\/www.esri.com\/arcgis-blog\/#website"},"datePublished":"2008-09-27T04:39:09+00:00","dateModified":"2018-12-18T19:59:26+00:00","breadcrumb":{"@id":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/mapping\/some-best-practices-for-working-with-dems#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.esri.com\/arcgis-blog\/"},{"@type":"ListItem","position":2,"name":"Some best practices for working with DEMs"}]},{"@type":"WebSite","@id":"https:\/\/www.esri.com\/arcgis-blog\/#website","url":"https:\/\/www.esri.com\/arcgis-blog\/","name":"ArcGIS Blog","description":"Get insider info from Esri product teams","publisher":{"@id":"https:\/\/www.esri.com\/arcgis-blog\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.esri.com\/arcgis-blog\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-US"},{"@type":"Organization","@id":"https:\/\/www.esri.com\/arcgis-blog\/#organization","name":"Esri","url":"https:\/\/www.esri.com\/arcgis-blog\/","logo":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.esri.com\/arcgis-blog\/#\/schema\/logo\/image\/","url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/04\/Esri.png","contentUrl":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/04\/Esri.png","width":400,"height":400,"caption":"Esri"},"image":{"@id":"https:\/\/www.esri.com\/arcgis-blog\/#\/schema\/logo\/image\/"},"sameAs":["https:\/\/www.facebook.com\/esrigis\/","https:\/\/x.com\/ESRI","https:\/\/www.linkedin.com\/company\/5311\/"]},{"@type":"Person","@id":"https:\/\/www.esri.com\/arcgis-blog\/#\/schema\/person\/cb24d44b9b7464f8eafd9fde29ae5c7a","name":"Charlie Frye","image":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.esri.com\/arcgis-blog\/#\/schema\/person\/image\/","url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/04\/CF_R3.png","contentUrl":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2018\/04\/CF_R3.png","caption":"Charlie Frye"},"description":"I am the Chief Cartographer at Esri and work on the Living Atlas Team. I have been with Esri in Software Products since 1994. I specialize in GIS engineering and information product design. I am the author of many global scientific and thematic layers on topics that include ecosystems, landforms, population, climate, emissions, etc. Contact me at cfrye@esri.com with questions or feedback.","knowsAbout":["ArcGIS"],"knowsLanguage":["English"],"jobTitle":"Distinguished GIS Engineer and Chief Cartographer","worksFor":"Environmental Systems Research Institute, Inc.","url":"https:\/\/www.esri.com\/arcgis-blog\/author\/cfrye"}]}},"text_date":"September 26, 2008","author_name":"Charlie Frye","author_page":"https:\/\/www.esri.com\/arcgis-blog\/author\/cfrye","custom_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/08\/Newsroom-Keyart-Wide-1920-x-1080.jpg","primary_product":"ArcMap","tag_data":[{"term_id":38211,"name":"ArcGIS Methods","slug":"arcgis-methods","term_group":0,"term_taxonomy_id":38211,"taxonomy":"post_tag","description":"","parent":0,"count":48,"filter":"raw"},{"term_id":24131,"name":"digital elevation model (DEM)","slug":"dem","term_group":0,"term_taxonomy_id":24131,"taxonomy":"post_tag","description":"","parent":0,"count":32,"filter":"raw"},{"term_id":24141,"name":"elevation","slug":"elevation","term_group":0,"term_taxonomy_id":24141,"taxonomy":"post_tag","description":"","parent":0,"count":57,"filter":"raw"},{"term_id":23211,"name":"Map Data","slug":"map-data","term_group":0,"term_taxonomy_id":23211,"taxonomy":"post_tag","description":"","parent":0,"count":35,"filter":"raw"}],"category_data":[{"term_id":22941,"name":"Mapping","slug":"mapping","term_group":0,"term_taxonomy_id":22941,"taxonomy":"category","description":"","parent":0,"count":2690,"filter":"raw"}],"product_data":[{"term_id":36991,"name":"ArcMap","slug":"arcgis-desktop","term_group":0,"term_taxonomy_id":36991,"taxonomy":"product","description":"","parent":36981,"count":325,"filter":"raw"}],"primary_product_link":"https:\/\/www.esri.com\/arcgis-blog\/?s=#&products=arcgis-desktop","_links":{"self":[{"href":"https:\/\/www.esri.com\/arcgis-blog\/wp-json\/wp\/v2\/blog\/187771","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.esri.com\/arcgis-blog\/wp-json\/wp\/v2\/blog"}],"about":[{"href":"https:\/\/www.esri.com\/arcgis-blog\/wp-json\/wp\/v2\/types\/blog"}],"author":[{"embeddable":true,"href":"https:\/\/www.esri.com\/arcgis-blog\/wp-json\/wp\/v2\/users\/4351"}],"replies":[{"embeddable":true,"href":"https:\/\/www.esri.com\/arcgis-blog\/wp-json\/wp\/v2\/comments?post=187771"}],"version-history":[{"count":0,"href":"https:\/\/www.esri.com\/arcgis-blog\/wp-json\/wp\/v2\/blog\/187771\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.esri.com\/arcgis-blog\/wp-json\/wp\/v2\/media?parent=187771"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.esri.com\/arcgis-blog\/wp-json\/wp\/v2\/categories?post=187771"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.esri.com\/arcgis-blog\/wp-json\/wp\/v2\/tags?post=187771"},{"taxonomy":"industry","embeddable":true,"href":"https:\/\/www.esri.com\/arcgis-blog\/wp-json\/wp\/v2\/industry?post=187771"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/www.esri.com\/arcgis-blog\/wp-json\/wp\/v2\/product?post=187771"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}