True Color - Corrected Reflectance (VIIRS / NOAA-20)

Overview and Intended Use This visualization represents a "true color" band combination (Red = I1, Green = M4, Blue = M3) of data collected by the VIIRS instrument on NOAA’s Joint Polar Satellite System (JPSS-1) satellite, which was renamed to NOAA-20 once on orbit. The imagery is most similar to how we see the Earth’s surface with our own eyes. It is a natural looking image that is useful at a global and regional scale. At its highest resolution, this visualization represents the underlying data scaled to a resolution of 250m per pixel at the equator. The VIIRS Corrected Reflectance product provides natural-looking images by removing gross atmospheric effects such as Rayleigh scattering from the visible bands. By contrast the VIIRS Surface Reflectance product, also available in the Living Atlas, provides a more complete atmospheric correction algorithm that includes aerosol correction and is designed to derive land surface properties. In clear atmospheric conditions the Corrected Reflectance product is similar to the Surface Reflectance product, but they depart from each other in the presence of aerosols. Multi-Spectral Bands The following table lists the VIIRS bands that are utilized to create this visualization. See here for a full description of all VIIRS bands. Band Description Wavelength (µm) Resolution (m) I3 Shortwave IR (Red) 1.58 - 1.64 375 M3 Visible / Reflective 0.478 - 0.488 750 M4 Visible / Reflective 0.545 - 0.565 750 Temporal Coverage and Limitations of Use By default, this layer will display the imagery currently available for today’s date. The update frequency of the imagery is a "daily composite" that is assembled from hundreds of individual data files. When viewing imagery for “today,” you may notice that only a portion of the map has imagery. This is because the visualization is continually updated as the satellite collects more data. To view imagery over time, you can update the layer properties to enable time animation and configure time settings. The current version of this layer is available from present back to April 25th, 2020. In the coming months, this will be extended to the start of the mission (November 18th, 2017). Source: NASA Global Imagery Browse Services (GIBS), NASA Worldview, & NASA LANCE This visualization is provided through the NASA Global Imagery Browse Services (GIBS), which are a set of standard services to deliver global, full-resolution satellite imagery for hundreds of NASA Earth science datasets and science parameters. Through its services, and the NASA Worldview client, GIBS enables interactive exploration of NASA's Earth imagery for a broad range of users. The data and imagery are generated within 3 hours of acquisition through the NASA LANCE capability. Esri and NASA Collaborative Services This visualization is made available through an ArcGIS image service hosted on Esri servers and facilitates access to a NASA GIBS service endpoint. For each image service request, the Esri server issues multiple requests to the GIBS service, processes and assembles the responses, and returns a proper mosaic image to the user. Processing occurs on-the-fly for each and every request to ensure that any update to the GIBS imagery is immediately available to the user. As such, availability of this visualization is dependent on both the Esri and the NASA GIBS services.概述与预期用途 本可视化展示了搭载于美国国家海洋和大气管理局（NOAA）联合极地卫星系统（JPSS-1，入轨后更名为NOAA-20）的可见光红外成像辐射仪（Visible Infrared Imaging Radiometer Suite，VIIRS）采集的“真彩色”波段组合数据，波段设置为红通道I1、绿通道M4、蓝通道M3。该影像与人类肉眼观测到的地球地表观感高度一致，属于自然逼真的图像，适用于全球及区域尺度的分析。在最高分辨率下，该可视化的原始数据在赤道处被缩放至每像素250米的分辨率。 VIIRS校正反射率产品通过去除可见光波段的瑞利散射等显著大气效应，生成观感自然的影像。与之相对，同样可在Living Atlas中获取的VIIRS地表反射率产品采用了更完整的大气校正算法，包含气溶胶校正，旨在反演陆地地表属性。在大气洁净的条件下，校正反射率产品与地表反射率产品效果相近，但在存在气溶胶时，二者的结果会出现差异。 多光谱波段 下表列出了用于生成本可视化的VIIRS波段，完整的VIIRS波段说明可参见此处。 | 波段 | 波段描述 | 波长（μm） | 分辨率（m） | |------|----------|-----------|------------| | I3 | 短波红外（红通道） | 1.58 - 1.64 | 375 | | M3 | 可见光/反射波段 | 0.478 - 0.488 | 750 | | M4 | 可见光/反射波段 | 0.545 - 0.565 | 750 | 时间覆盖范围与使用限制 默认情况下，该图层将显示当前日期可用的最新影像。影像更新频率为“每日合成”，由数百个独立数据文件拼接而成。当查看“今日”的影像时，可能仅能看到地图的部分区域有影像，这是因为该可视化会随着卫星采集更多数据而持续更新。若要查看随时间变化的影像，可更新图层属性以启用时间动画并配置时间设置。当前版本的该图层可获取的时间范围为2020年4月25日至今，未来数月内，该时间范围将扩展至任务起始日（2017年11月18日）。 数据来源：美国国家航空航天局（NASA）全球影像浏览服务（Global Imagery Browse Services，GIBS）、NASA Worldview及NASA LANCE 本可视化通过NASA全球影像浏览服务（GIBS）提供，该服务是一套标准服务集，可为数百个NASA地球科学数据集及科学参数提供全球全分辨率卫星影像。通过其服务及NASA Worldview客户端，GIBS可支持广大用户交互式探索NASA地球影像。数据及影像在采集后3小时内即可通过NASA LANCE功能生成。 Esri与NASA合作服务 本可视化通过托管于Esri服务器的ArcGIS影像服务提供，可对接NASA GIBS服务端点。每一次影像服务请求时，Esri服务器都会向GIBS服务发起多个请求，处理并拼接响应结果，最终向用户返回完整的镶嵌影像。每次请求均实时处理，以确保GIBS影像的任何更新均可立即对用户可见。因此，本可视化的可用性同时依赖于Esri与NASA GIBS两项服务。