True Color - Surface 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 represents a natural looking view of the Earth's surface without the presence of aerosols (e.g. clouds and dust). At its highest resolution, this visualization represents the underlying data scaled to a resolution of 500m per pixel at the equator. The MODIS Surface Reflectance product is created by an atmospheric correction algorithm that includes aerosol correction and is designed to derive land surface properties. By contrast, the MODIS Corrected Reflectance product, which is also available in the Living Atlas, provides more natural-looking images by only removing gross atmospheric effects such as Rayleigh scattering from the visible bands. 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 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"波段组合方案（红色波段对应波段1、绿色对应波段4、蓝色对应波段3）。该影像呈现了地表的自然视觉效果，未受气溶胶（如云、沙尘）干扰。在最高分辨率下，本可视化成果的原始数据经缩放后，在赤道区域的像素分辨率为500米。 MODIS地表反射率产品（Surface Reflectance）通过包含气溶胶校正的大气校正算法生成，旨在反演地表属性参数。与之相比，同样可在全球动态地图集（Living Atlas）中获取的MODIS校正反射率产品（Corrected Reflectance）仅通过去除可见光波段的瑞利散射等显著大气效应，即可生成视觉效果更自然的影像。在大气通透的条件下，校正反射率产品与地表反射率产品效果相近，但当存在气溶胶时，二者的输出结果会出现差异。 多光谱波段 下表列出了用于生成本可视化成果的MODIS波段，如需查看所有MODIS波段的完整说明，请点击此处。 | 波段 | 描述 | 波长（μm） | 分辨率（m） | |------|------|------------|------------| | 1 | 可见光（红） | 0.620 - 0.670 | 250 | | 3 | 可见光（蓝） | 0.459 - 0.479 | 500 | | 4 | 可见光（绿） | 0.545 - 0.565 | 500 | 时间覆盖范围 默认情况下，本图层将显示当日可用的最新影像。该影像的更新频率为"每日合成"，由数百份独立数据文件拼接而成。当查看"当日"影像时，您可能会发现仅部分地图区域显示了影像，这是因为可视化成果会随着卫星采集更多数据而持续更新。如需查看不同时段的影像，您可通过更新图层属性启用时间动画功能并配置时间参数。本图层的当前版本可获取的时间范围为自任务启动之日（2002年7月3日）起至今。 数据来源：NASA全球影像浏览服务（GIBS）、NASA Worldview平台及NASA LANCE系统 本可视化成果由NASA全球影像浏览服务（GIBS）提供，该服务是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。依托该服务体系与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，采集到的卫星数据可在3小时内生成影像成果。 Esri与NASA合作服务 本可视化成果通过部署于Esri服务器的ArcGIS影像服务提供，便于用户访问NASA GIBS服务端点。针对每一次影像服务请求，Esri服务器将向GIBS服务发起多轮请求，对返回结果进行处理与拼接后，向用户返回完整的镶嵌影像。所有请求均采用实时动态处理模式，以确保GIBS影像的任何更新均可立即向用户开放。因此，本可视化成果的可用性同时依赖于Esri服务与NASA GIBS服务。