True Color - Corrected Reflectance (MODIS / Aqua)

Overview and Intended Use This visualization represents a "true color" band combination (Red = 1, Green = 4, Blue = 3) of data collected by the MODIS instrument on the NASA Aqua satellite. 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 MODIS Corrected Reflectance product provides natural-looking images by removing gross atmospheric effects such as Rayleigh scattering from the visible bands. By contrast, the MODIS Surface Reflectance product, which is 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 MODIS bands that are utilized to create this visualization. See here for a full description of all MODIS bands. Band Description Wavelength (µm) Resolution (m) 1 Visible (Red) 0.620 - 0.670 250 3 Visible (Blue) 0.459 - 0.479 500 4 Visible (Green) 0.545 - 0.565 500 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 the start of the mission (July 3rd, 2002). 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 本可视化成果基于美国国家航空航天局（NASA）Aqua卫星搭载的中分辨率成像光谱仪（MODIS）采集的数据，采用真彩色波段组合（红=1、绿=4、蓝=3）生成。该影像与人类肉眼观测地球表面的视觉效果高度一致，是一幅视觉效果自然的影像，适用于全球及区域尺度的研究与展示。在最高分辨率下，该可视化成果基于赤道处每像素250米的比例尺缩放后的原始数据生成。 MODIS校正反射率产品可通过去除可见光波段的瑞利散射等显著大气效应，生成视觉效果自然的影像。与之相比，ArcGIS生活地图集（Living Atlas）中提供的MODIS地表反射率产品采用了更完善的大气校正算法，包含气溶胶校正环节，旨在反演陆地表面属性。在大气条件晴朗时，校正反射率产品与地表反射率产品效果相近，但在存在气溶胶的场景下，二者会出现明显差异。 ## 多光谱波段 以下列出用于生成该可视化成果的MODIS波段。点击此处可查看所有MODIS波段的完整说明。 | 波段编号 | 描述 | 波长（μm） | 分辨率（m） | | :---: | :---: | :---: | :---: | | 1 | 可见光（红光） | 0.620-0.670 | 250 | | 3 | 可见光（蓝光） | 0.459-0.479 | 500 | | 4 | 可见光（绿光） | 0.545-0.565 | 500 | ## 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。该影像的更新频率为每日合成产品，由数百份独立数据文件拼接而成。当查看“今日”影像时，您可能会发现地图仅部分区域覆盖有影像，这是因为随着卫星收集更多数据，该可视化成果会持续更新。若需查看不同时段的影像，您可修改图层属性以启用时间动画功能，并配置时间参数。该图层的当前版本可获取的时间范围为自2002年7月3日任务启动至今。 ## 数据来源 NASA全球影像浏览服务（GIBS）、NASA Worldview及NASA LANCE 本可视化成果由NASA全球影像浏览服务（GIBS）提供，该服务为一套标准化服务体系，可面向数百项NASA地球科学数据集与科学参数提供全球全分辨率卫星影像。通过该服务及NASA Worldview客户端，GIBS可为广大用户提供NASA地球影像的交互式浏览功能。依托NASA LANCE系统，数据与影像可在采集后3小时内完成生成。 ## Esri与NASA合作服务 本可视化成果通过Esri服务器托管的ArcGIS影像服务提供，可便捷访问NASA GIBS服务端点。针对每一次影像服务请求，Esri服务器会向GIBS服务发起多次请求，对返回结果进行处理与拼接，最终向用户返回完整的镶嵌影像。每一次请求均会实时处理，以确保GIBS影像的任何更新都能立即对用户可见。因此，本可视化成果的可用性同时依赖于Esri与NASA GIBS两项服务。