"},{"ID":108651,"user_firstname":"Jeffrey","user_lastname":"Swain","nickname":"Jeff Swain","user_nicename":"jswain","display_name":"Jeff Swain","user_email":"JSwain@esri.com","user_url":"https:\/\/www.esri.com\/arcgis-blog\/?s=#&author=jswain","user_registered":"2020-10-05 20:10:08","user_description":"A Product Engineer on the Raster Team, who has been with Esri in various capacities since 2009, including as an Esri Support Analyst, and an Author for Esri Training Services. \r\n\r\nI find joy in solving problems through imagery and shared understanding, always driven by a passion to make things work better. I'm grateful for the creative minds I've met along the way\u2014collaboration has shown me that the best solutions are often born from many voices working together.","user_avatar":"
"}],"short_description":"Using Sentinel-2 Level-2A from Living Atlas and raster function template to detect flooded areas in Map Viewer of ArcGIS Online.","flexible_content":[{"acf_fc_layout":"content","content":"Change Detection Multispectral ArcGIS Online<\/h2>\n
Change Detection Multispectral ArcGIS Online<\/strong>\u00a0is a custom raster function template.\u00a0The workflow of detecting changes from two multispectral imagery involves multiple raster functions. We have consolidated these functions into this template and made it available to everyone. It takes analysis-ready multispectral images, either from Sentinel-2 Level-2A or Landsat Level-2 from ArcGIS Living Atlas as input. You don\u2019t need to prepare your own data to perform change analysis.<\/p>\n Detailed information about Change Detection Multispectral ArcGIS Online<\/strong>\u00a0is here<\/a>.<\/p>\n"},{"acf_fc_layout":"image","image":{"ID":2899622,"id":2899622,"title":"rft-layout3","filename":"rft-layout3.jpg","filesize":34134,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/rft-layout3.jpg","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-living-atlas\/imagery\/detect-changes-with-arcgis-living-atlas-and-raster-function-template-in-arcgis-online\/rft-layout3","alt":"change detection multispectral AGOL","author":"370032","description":"","caption":"Change Detection Multispectral AGOL","name":"rft-layout3","status":"inherit","uploaded_to":2737082,"date":"2025-07-16 21:04:51","modified":"2025-07-18 17:10:47","menu_order":0,"mime_type":"image\/jpeg","type":"image","subtype":"jpeg","icon":"https:\/\/www.esri.com\/arcgis-blog\/wp-includes\/images\/media\/default.png","width":1192,"height":374,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/rft-layout3-213x200.jpg","thumbnail-width":213,"thumbnail-height":200,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/rft-layout3.jpg","medium-width":464,"medium-height":146,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/rft-layout3.jpg","medium_large-width":768,"medium_large-height":241,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/rft-layout3.jpg","large-width":1192,"large-height":374,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/rft-layout3.jpg","1536x1536-width":1192,"1536x1536-height":374,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/rft-layout3.jpg","2048x2048-width":1192,"2048x2048-height":374,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/rft-layout3-826x259.jpg","card_image-width":826,"card_image-height":259,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/rft-layout3.jpg","wide_image-width":1192,"wide_image-height":374}},"image_position":"center","orientation":"horizontal","hyperlink":""},{"acf_fc_layout":"content","content":" In this blog, we use this template to detect changes caused by floods in Asheville, North Carolina. Hurricane Helene hit this area on September 27, 2024. To achieve this goal, we need two image layers, before and after Helene, to retrieve the changes. We call them “before image” and “after image”. They are selected from Sentinel-2 Level-2A in ArcGIS Living Atlas. The analysis is done in Map Viewer. The workflow is suitable for detecting other types of changes as well with proper spectral index and band indexes set in Band Arithmetic<\/strong>.<\/p>\n"},{"acf_fc_layout":"content","content":" Note: Cloud removal is not included in this blog. We are able to find the best scenes for the before and after images . If clear scenes are not available for your area of interest (AOI) for certain dates, you can adjust the dates to try. If you still cannot obtain clear images, you will need to remove clouds first before performing change detection.<\/p>\n"},{"acf_fc_layout":"content","content":" To detect changes in ArcGIS Online, we need the tools below. They are in the right side tool pane in Map Viewer.<\/p>\n Map Viewer is an integrated app within ArcGIS Online. You can use it to display web maps and create new ones by adding all kinds of layers. The truly cool aspect is that it also provides powerful tools that allow you to perform various analyses. The change detection here is completed entirely within Map Viewer. To do analysis, your user type in ArcGIS Online must be Professional or Professional Plus.<\/p>\n We are detecting floods in Asheville, North Carolina. So, our AOI is the Asheville area.<\/p>\n Follow the steps below to add data source Sentinel-2 Level-2A to the map. If you need to know more about adding data from ArcGIS Living Atlas, read this tutorial<\/a>.<\/p>\n The Sentinel layer has thousands of scenes. We need to create a subset from it based on the AOI and filter the scenes based on the dates near the hurricane so that we can easily select the best scenes for before image and after image in step 5 and step 6.<\/p>\n We first inspect the candidate scenes in September, then select the best one from them.<\/p>\n These selected scenes can be saved within the web map or you can save them to your organization to use them in other web maps. Select the image in the Layers pane, click the More Properties button, and select Save As to save it in your organization. This saved imagery layer is a version of the Sentinel 2A layer saved to your organization. This process is useful if you want to maintain access to that scene in the future. <\/p>\n"},{"acf_fc_layout":"content","content":" Now, we add Oct 2, 7, 12, 17, 22, and 27 to the map and select the best one from them using the same methods from step 5.<\/p>\n <\/p>\n"},{"acf_fc_layout":"content","content":" Zoom into the Asheville Regional Airport area in the south of Asheville, and switch between Before image<\/strong><\/em> and After image<\/strong><\/em>. The flooding areas on After image<\/em><\/strong> are striking. Now we have layers like this below. We will use this area as the processing extent.<\/p>\n"},{"acf_fc_layout":"image","image":{"ID":2887932,"id":2887932,"title":"Asheville","filename":"Asheville.jpg","filesize":398022,"url":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/Asheville.jpg","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-living-atlas\/imagery\/detect-changes-with-arcgis-living-atlas-and-raster-function-template-in-arcgis-online\/asheville","alt":"","author":"370032","description":"","caption":"Asheville south on After image","name":"asheville","status":"inherit","uploaded_to":2737082,"date":"2025-07-09 21:10:56","modified":"2025-07-09 21:11:43","menu_order":0,"mime_type":"image\/jpeg","type":"image","subtype":"jpeg","icon":"https:\/\/www.esri.com\/arcgis-blog\/wp-includes\/images\/media\/default.png","width":1661,"height":847,"sizes":{"thumbnail":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/Asheville-213x200.jpg","thumbnail-width":213,"thumbnail-height":200,"medium":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/Asheville.jpg","medium-width":464,"medium-height":237,"medium_large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/Asheville.jpg","medium_large-width":768,"medium_large-height":392,"large":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/Asheville.jpg","large-width":1661,"large-height":847,"1536x1536":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/Asheville-1536x783.jpg","1536x1536-width":1536,"1536x1536-height":783,"2048x2048":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/Asheville.jpg","2048x2048-width":1661,"2048x2048-height":847,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/Asheville-826x421.jpg","card_image-width":826,"card_image-height":421,"wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/Asheville.jpg","wide_image-width":1661,"wide_image-height":847}},"image_position":"center","orientation":"horizontal","hyperlink":""},{"acf_fc_layout":"content","content":" To do raster analysis, we need raw data without any template applied. Processing templates apply other raster functions on the input images to alter the display. Depending on the raster analysis you want to perform, the input raster bands may not be available for analysis. For example, the Natural Color processing template uses only 3 of the available 11 raster bands (Red, Green, and Blue). Since you will be using a raster band calculation that includes the short wave infrared and near infrared bands, you will need to remove the processing template so that those bands are available for analysis.\u00a0 To remove the applied template, follow these steps:<\/p>\n Add Change Detection Multispectral ArcGIS Online<\/strong> to the map by following these steps. For how to create a raster function template in ArcGIS Pro, reference this document<\/a>. To create a raster function template in ArcGIS Online, reference this document<\/a>. To download the raster function, find it here<\/a>.<\/p>\n Click one Band Arithmetic<\/strong>, and select Properties<\/strong>.<\/p>\n As you’ll see, the spectral index NDWI is pre-selected for Method<\/strong> because the template will detect floods. It uses band 8 (NIR) and band 3 (Green) from Sentinel imagery for Band indexes<\/strong>. We don’t need to change anything for this demo. Close the Properties window.<\/p>\n Now, we provide parameters for the template, then run it.<\/p>\n Before image<\/strong> and After image<\/strong> are currently gray. We need to display them in natural colors so we can see the result layer nicely overlapped on them, which helps to better interpret and evaluate the result layer.<\/p>\n <\/p>\n"},{"acf_fc_layout":"content","content":" We have demonstrated how to detect flooded areas by using Change Detection Multispectral ArcGIS Online <\/strong>with imagery layers from Sentinel-2 Level-2A in ArcGIS Living Atlas as input in Map Viewer of ArcGIS Online.<\/p>\n You can use the same template to detect floods in other areas in the world. You just need to select two new images according to the AOI and the date when the flood happens, then execute the template.<\/p>\n"},{"acf_fc_layout":"content","content":" With this raster function template, you can also detect other changes that use spectral indexes for example, burn scars. In the Properties<\/strong> of Band Arithmetic<\/strong>, you just need to choose NBR for Method<\/strong>, and specify 12(SWIR) and 8 (NIR) for Band indexes<\/strong>. (Reference the document<\/a> for Sentinel-2 band description, the document<\/a> for spectral indexes).\u00a0 Save the changes. If you use Landsat Level-2<\/strong> from ArcGIS Living Atlas as the data source, band indexes will be different. For NDWI, band 5 and 3 will be used, and for NBR, band 6 or 7 and 5 will be used. (Reference the description of Landsat Level-2 at here<\/a>). You also can try different values for mask criteria, instead of 0.09.<\/p>\n In summary, by using ArcGIS Living Atlas and the power of raster function templates, you can do many kinds of change detection analysis in Map Viewer of ArcGIS Online.<\/p>\n"}],"related_articles":[{"ID":552882,"post_author":"5991","post_date":"2019-07-10 13:48:08","post_date_gmt":"2019-07-10 20:48:08","post_content":"","post_title":"Use raster function templates to assess vegetation for wildlife habitat","post_excerpt":"","post_status":"publish","comment_status":"closed","ping_status":"closed","post_password":"","post_name":"use-raster-function-templates-to-assess-vegetation-for-wildlife-habitat","to_ping":"","pinged":"","post_modified":"2022-08-25 13:53:55","post_modified_gmt":"2022-08-25 20:53:55","post_content_filtered":"","post_parent":0,"guid":"https:\/\/www.esri.com\/arcgis-blog\/?post_type=blog&p=552882","menu_order":0,"post_type":"blog","post_mime_type":"","comment_count":"0","filter":"raw"},{"ID":1932982,"post_author":"108651","post_date":"2023-12-05 06:00:48","post_date_gmt":"2023-12-05 14:00:48","post_content":"","post_title":"New to raster analysis in ArcGIS Online? Here are five tips to get you started.","post_excerpt":"","post_status":"publish","comment_status":"open","ping_status":"closed","post_password":"","post_name":"tips-to-use-raster-analysis-tools-wisely","to_ping":"","pinged":"","post_modified":"2024-08-20 09:02:35","post_modified_gmt":"2024-08-20 16:02:35","post_content_filtered":"","post_parent":0,"guid":"https:\/\/www.esri.com\/arcgis-blog\/?post_type=blog&p=1932982","menu_order":0,"post_type":"blog","post_mime_type":"","comment_count":"0","filter":"raw"},{"ID":2743462,"post_author":"7641","post_date":"2025-04-08 12:18:17","post_date_gmt":"2025-04-08 19:18:17","post_content":"","post_title":"Learn to explore Sentinel-2 imagery using Sentinel-2 Explorer","post_excerpt":"","post_status":"publish","comment_status":"closed","ping_status":"closed","post_password":"","post_name":"learn-sentinel-2-explorer","to_ping":"","pinged":"","post_modified":"2025-07-07 16:37:58","post_modified_gmt":"2025-07-07 23:37:58","post_content_filtered":"","post_parent":0,"guid":"https:\/\/www.esri.com\/arcgis-blog\/?post_type=blog&p=2743462","menu_order":0,"post_type":"blog","post_mime_type":"","comment_count":"0","filter":"raw"}],"show_article_image":true,"card_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/08\/original-screenshot-16-9-826by465.png","wide_image":"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/08\/original-screenshot-16-9-1920by1080.png"},"yoast_head":"\nKey steps<\/h2>\n
\n
Tools needed<\/h2>\n
\n
Detailed steps<\/h2>\n
Step 1: Open Map Viewer<\/h3>\n
\n
Step 2: Decide area of interest (AOI)<\/h3>\n
\n
\n
Step 3: Add the Sentinel-2 Level-2A layer to map<\/h3>\n
\n
![\"\"](\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/add-sentinel-2.jpg\")
![\"\"](\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/save.jpg\")
Step 4: Use Filter to select a subset of the Sentinel-2 Level-2A layer<\/h3>\n
\n
![\"\"](\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/filters-by-acquisition-date.jpg\")
Step 5: Select a scene from the subset as before image<\/h3>\n
\n
![\"\"](\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/add-tile2.jpg\")
![\"\"](\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/rename-layer.jpg\")
Step 6: Select a scene from the subset as after image<\/h3>\n
\n
Step 7: Remove Natural Color template from Before image and After image<\/h3>\n
\n
![\"\"](\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/processing-none.jpg\")
Step 8: Add the change detection template to the map<\/h3>\n
\n
![\"\"](\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/browse-rft.jpg\")
![\"BA](\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/rft-properties-1.jpg\")
![\"band](\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/band-arithmetic2.jpg\")
Step 9: Detect flooded areas by running the template<\/h3>\n
\n
![\"rft](\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/rft-open3.jpg\")
![\"rft](\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/rft-input2.jpg\")
![\"\"](\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/rft-result-1.jpg\")
Step 10: Resume the display of the two input layers<\/h3>\n
\n
![\"floods\"](\"https:\/\/www.esri.com\/arcgis-blog\/app\/uploads\/2025\/07\/rft-result-display.jpg\")
Summary<\/h2>\n