{ "id": "18a291917a2b49e88177e028d0b126ad", "item": "18a291917a2b49e88177e028d0b126ad", "itemType": "text", "owner": "esri_en", "uploaded": 1527739811000, "modified": 1527739811000, "guid": null, "name": null, "title": "Image Mask", "type": "Web Mapping Application", "typeKeywords": [ "Configurable", "createAppWithoutMap", "interpret", "JavaScript", "Map", "Mapping Site", "Online Map", "sourceId#8e3a6ab7b10c449bbfa0fa72b2b820af", "Web Map" ], "description": "
Image Mask is a configurable app template for identifying areas of an image that have changed over time or that meet user-set thresholds for calculated spectral indexes. The template also includes tools for measurement, recording locations, and more.<\/div>

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App users can zoom to bookmarked areas of interest (or search for their own), select any of the imagery layers from the associated web map to analyze, use a time slider or dropdown menu to select images, then choose between the Change Detection or Mask tools to produce results.<\/div>

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Image Mask users can do the following:<\/span><\/div>
  • Zoom to bookmarked areas of interest (or bookmark their own)<\/li>
  • Select specific images from a layer to visualize (search by date or another attribute)<\/li>
  • Use the Change Detection tool to compare two images in a layer (see options, below)<\/li>
  • Use the Mask tool to highlight areas that meet a user-set threshold for common spectral indexes (NDVI, SAVI, a burn index, and a water index). For example, highlight all the areas in an image with NDVI values above 0.25 to find vegetation.
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  • Annotate imagery using editable feature layers<\/li>
  • Perform image measurement on imagery layers that have mensuration capabilities<\/li>
  • Export an imagery layer to the user's local machine, or as a layer in the user\u2019s ArcGIS account<\/li><\/ul>
    Use Cases<\/span><\/div>
    • A student investigating urban expansion over time using Esri\u2019s Multispectral Landsat image service<\/li>
    • A farmer using NAIP imagery to examine changes in crop health<\/li>
    • An image analyst recording burn scar extents using satellite imagery<\/li>
    • An aid worker identifying regions with extreme drought to focus assistance<\/li><\/ul>
      Change detection methods<\/span><\/span><\/div>
      <\/span><\/span>For each imagery layer, give app users one or more of the following change detection options:<\/div>
      • Image Brightness (calculates the change in overall brightness)<\/li>
      • Vegetation Index (NDVI) (requires red and infrared bands)<\/li>
      • Soil-Adjusted Vegetation Index (SAVI) (requires red and infrared bands)<\/li>
      • Water Index (requires green and short-wave infrared bands)<\/li>
      • Burn Index (requires infrared and short-wave infrared bands)
        <\/li><\/ul>
        For each of the indexes, users also have a choice between three modes:<\/div>
        • Difference Image: <\/b> calculates increases and decreases for the full extent <\/li>
        • Difference Mask: <\/b> users can focus on significant change by setting the minimum increase or decrease to be masked\u2014for example, a user could mask only areas where NDVI increased by at least 0.2<\/li>
        • Threshold Mask: <\/b> The user sets a threshold and magnitude for what is masked as change. The app will only identify change that\u2019s above the user-set lower threshold and bigger than the user-set minimum magnitude.<\/li><\/ul>

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          Supported Devices<\/span><\/div>
          This application is responsively designed to support use in browsers on desktops, mobile phones, and tablets.<\/div><\/div>

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          Data Requirements<\/span>
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          Creating an app with this template requires a web map with at least one imagery layer.
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          Get Started<\/span> <\/div>
          This application can be created in the following ways:<\/div>
          1. Click the Create a Web App button on this page
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          2. Share a map and choose to create a web app
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          3. On the Content<\/b> page, click Create - App - From Template <\/b>
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          4. Click the Download<\/b> button to access the source code. Do this if you want to host the app on your own server and optionally customize it to add features or change styling.
            <\/li><\/ol><\/div><\/div><\/div><\/div>

            <\/span><\/div><\/div>

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