1 數(shù)據(jù)下載

根據(jù)時(shí)間選擇不同的Landsat衛(wèi)星傳感器

PS：2003 年5 月31 日(21:42:35 GMT)，Landsat-7ETM+ 機(jī)載掃描行校正器(ScanLinesCorrector, 簡稱SLC) 突然發(fā)生故障，導(dǎo)致獲取的圖像出現(xiàn)數(shù)據(jù)重疊和大約25% 的數(shù)據(jù)丟失，因此2003.5.31日之后Landsat 7的所有數(shù)據(jù)都是異常的，需要采用SLC-off模型校正。另外，2003.05.31-2003.07.14以及2003.07.03-2003.09.17之間的數(shù)據(jù)是沒有獲得。對(duì)于已經(jīng)丟失的數(shù)據(jù)，沒有可能找回實(shí)際數(shù)據(jù)，因此，只能利用縫隙填充的方式進(jìn)行差值，盡量彌補(bǔ)缺失的數(shù)據(jù)部分，并且使相對(duì)完好的70-80%數(shù)據(jù)可用。可以用數(shù)據(jù)修補(bǔ)補(bǔ)丁Tm_Destripe修復(fù)丟失的數(shù)據(jù)

Landsat8數(shù)據(jù)介紹

根據(jù)經(jīng)緯度選擇對(duì)應(yīng)的條帶：

Lansdat Analysis Ready Data (ARD) Tile Conversion Tool:把 Landsat WRS-2 path/rows 或者 latitude/longitude 坐標(biāo)轉(zhuǎn)換為對(duì)應(yīng)的Landsat ARD tiles.

Landsat Path/Row - Latitude/Longitude Conversion Tool:把 latitude/longitude 坐標(biāo)轉(zhuǎn)換為對(duì)應(yīng)的 Landsat path/rows 條帶

Spectral Characteristics Viewer 光譜特征瀏覽器

Spectral Characteristics Viewer: 輔助用戶針對(duì)他們的研究領(lǐng)域選擇最合適的衛(wèi)星波段，例如：

Landsat Data Access Portals 數(shù)據(jù)下載入口

	Landsat Collections Level-1 Scenes1	U.S. Landsat Analysis Ready Data Tiles2	Landsat Level-2 Scenes3 (Global)	U.S. Landsat Level-3 Tiles4
EarthExplorer 圖形界面，用于通過地址、郵政編碼、地名或使用地圖來定義感興趣的區(qū)域 查詢條件可以同時(shí)應(yīng)用于多個(gè)數(shù)據(jù)集，比較全，一般用這個(gè)即可	X	X	X*	X
GloVis 可視化瀏覽 可以選擇USGS遙感數(shù)據(jù)檔案的數(shù)據(jù)集	X
LandsatLook Viewer used to access Landsat data in the USGS archive	X
ESPA On-Demand Interface 能夠接受高級(jí)別數(shù)據(jù)處理要求的處理系統(tǒng)			X*
AppEEARS 允許用戶使用空間、時(shí)間和波段參數(shù)對(duì)地面反射率和像素級(jí)質(zhì)量評(píng)估數(shù)據(jù)進(jìn)行子集處理		X
BULK DATA ACCESS OPTIONS
EarthExplorer API (Request access to the APIHERE) Allows users to search and download imagery as well as retrieve metadata from the EROS inventory by using simple HTTP communications throughvarious programming languages	X	X		X
EarthExplorer Bulk Download Application (BDA) Useful for downloading large quantities of Landsat Level-1 scenes and can be used to automatically retrieve them with little to no user interaction	X	X		X
ESPA API Allows users to interact with using simple HTTP communications through the programming language of their choice			X*
ESPA Bulk Downloader Can be utilized to automatically download completed scenes			X*
*Processing required; immediate downloads not available 需要處理 不能立刻下載 1Landsat Collections Level-1 Scenes include:Top of Atmosphere (TOA) Reflectance 大氣層頂反射率 2U.S. Landsat Analysis Ready Data Tiles include:Top of Atmosphere (TOA) Reflectance,TOA Brightness Temperature,Surface Reflectance,Provisional Surface Temperature, and Pixel Quality Assessment 3Landsat Level-2 Scenes include:Surface Reflectance (on-demand processing), SR-derived Spectral Indices 4Landsat Level-3Tiles include:Dynamic Surface Water Extent, Burned Area, and Fractional Snow Covered Area
BULK METADATA ACCESS
Landsat Bulk Metadata Service Extract scene metadata from the Landsat inventory for Landsat-related datasets.	X	X

鏈接：https://www.usgs.gov/land-resources/nli/landsat/landsat-data-access?qt-science_support_page_related_con=0

也可以在地理空間數(shù)據(jù)云中下載

下載過程

選擇 時(shí)間范圍、區(qū)域（或者是圖像條帶號(hào)）、數(shù)據(jù)集、云的范圍 等對(duì)影像進(jìn)行篩選

結(jié)果最大返回?cái)?shù)量可是設(shè)置大一些，當(dāng)下載量較大時(shí)以免漏掉一些數(shù)據(jù)

Level-2級(jí)別產(chǎn)品則通過提交訂單下載

直接選擇最大的數(shù)據(jù)（最后一個(gè)）下載即可

產(chǎn)品信息

鏈接：https://www.usgs.gov/land-resources/nli/landsat/product-information

Landsat Collection 1

Landsat Collection 1 包括了來自Landsat 8 Operational Land Imager (OLI)/Thermal Infrared Sensor (TIRS), Landsat 7 Enhanced Thematic Mapper Plus (ETM+), Landsat 4-5 Thematic Mapper (TM)*和Landsat 1-5 Multispectral Scanner (MSS) 的Level-1 級(jí)別數(shù)據(jù)產(chǎn)品。Collection 確保了跨時(shí)間、儀器、文件名等的數(shù)據(jù)質(zhì)量一致性

Collection 1 Tiers

Landsat Collection Tiers 為一級(jí)數(shù)據(jù)產(chǎn)品的庫存結(jié)構(gòu)，基于數(shù)據(jù)質(zhì)量和處理水平。層定義的目的是支持更容易識(shí)別合適的場景進(jìn)行時(shí)間序列像元級(jí)分析，并提供臨時(shí)數(shù)據(jù)，這些數(shù)據(jù)在下行時(shí)立即處理，以便在有限校準(zhǔn)的緊急響應(yīng)情況下快速分發(fā)。

Real-Time (RT)

最近獲取的 Landsat 7 ETM+ 和 Landsat 8 OLI/TIRS 數(shù)據(jù)，但使用預(yù)測(cè)星歷(Landsat 7)、初始緩沖模式參數(shù)(Landsat 7)或初始TIRS視線模型參數(shù)(Landsat 8)。數(shù)據(jù)放置在實(shí)時(shí)層，可在12小時(shí)內(nèi)下載(通常為4-6小時(shí))。一旦使用確定的星歷、更新的緩沖模式參數(shù)和精化的TIRS參數(shù)對(duì)數(shù)據(jù)進(jìn)行了重新處理，產(chǎn)品將被轉(zhuǎn)換為第一層或第二層，并從實(shí)時(shí)層中刪除。從實(shí)時(shí)到第1層或第2層的轉(zhuǎn)換延遲在14到26天之間。后續(xù)處理細(xì)節(jié)如下所述。

Landsat 7 ETM+ 使用預(yù)測(cè)的星歷和初始緩沖模式參數(shù)立即處理獲取，并將其放入實(shí)時(shí)層。在初始處理后不久(大約1天)，使用確定的星歷對(duì)數(shù)據(jù)進(jìn)行重新處理，但保留實(shí)時(shí)層。在儀器走向/表征期間(約26天)，校準(zhǔn)參數(shù)調(diào)整完成幾何校正模型，并對(duì)數(shù)據(jù)進(jìn)行重新處理，將其放入Tier 1或Tier 2。
Landsat 8 TIRS 數(shù)據(jù)可能不符合與OLI共同注冊(cè)的規(guī)范。TIRS瞄準(zhǔn)線模型參數(shù)是根據(jù)兩周校準(zhǔn)演習(xí)期間獲得的數(shù)據(jù)進(jìn)行細(xì)化的，場景在獲取后的14到16天內(nèi)重新處理，并放置到第1層或第2層。

Tier 1 (T1) 一層

有最高可用數(shù)據(jù)質(zhì)量的Landsat影像被置于Tier 1，并適合用于進(jìn)行時(shí)間序列分析，Tier 1包括Level-1 精度和地形(L1TP)校正數(shù)據(jù)，這些數(shù)據(jù)具有良好的輻射測(cè)量特征，并在不同的Landsat儀器之間進(jìn)行過定標(biāo)。

Tier 2 (T2) 二層

處理中沒有達(dá)到 Tier 1 標(biāo)準(zhǔn)的Landsat 影像為 Tier 2. Tier 2 和 Tier 1 的輻射標(biāo)準(zhǔn)相同, 沒有達(dá)到 Tier 1 的幾何標(biāo)準(zhǔn)，這是由于缺少準(zhǔn)確的軌道信息 (特別是Landsat較老的傳感器), 大范圍的云層覆蓋, 地面控制點(diǎn)不夠等. 它包括 Systematic Terrain (L1GT) and Systematic (L1GS) 處理數(shù)據(jù). 用戶可以查詢 RMSE等屬性來決定該數(shù)據(jù)的適用性。

Collection 1產(chǎn)品名字標(biāo)識(shí)

Landsat Level-1 Processing Levels

Processing Level	Description
Terrain Precision Correction 地形精度校正 (L1TP)	利用地面控制點(diǎn)(GCPs)和數(shù)字高程模型(DEM)數(shù)據(jù)進(jìn)行輻射和正射校正，以校正地形位移。 最適合像元級(jí)時(shí)間序列分析的質(zhì)量最高的一級(jí)產(chǎn)品。 GCPs 來自于 Global Land Survey 2000 (GLS2000)數(shù)據(jù)集. Landsat 處理 DEM 源包括: Shuttle Radar Topography Mission (SRTM) National Elevation Dataset (NED) Canadian Digital Elevation Data (CDED) Digital Terrain Elevation Data (DTED) Global 30 Arc-Second Elevation Data Set (GTOPO30) Greenland Ice sheet Mapping Project (GIMP)
Systematic Terrain Correction 系統(tǒng)地形校正 (L1GT)	Radiometrically calibrated with systematic geometric corrections applied using the spacecraft ephemeris data and DEM data to correct for relief displacement. Note: L1GT 對(duì)于 Landsat 7 和Landsat 8 scenes是最高級(jí)別的輻射定標(biāo)和系統(tǒng)校正 The L1GT product uses the high-resolution Radarsat Antarctic Mapping Project (RAMP) Version 2 as the elevation correction source.
Geometric Systematic Correction 幾何系統(tǒng)校正 (L1GS)	Radiometrically calibration with only systematic geometric corrections applied using the spacecraft ephemeris data

Standard Processing Parameters

所有Landsat 1-8 Collection 1 Level-1產(chǎn)品由 Landsat Product Generation System (LPGS) 使用以下參數(shù)生產(chǎn):

Georeferenced Tagged Image File Format (GeoTIFF)
Cubic convolution (CC)
Universal Transverse Mercator (UTM) map projection (Stereographic is used for scenes with a center latitude greater than or equal to -63.0 degrees)
World Geodetic System (WGS) 84 datum

MAP (North-up) image orientation

Landsat Level-1 數(shù)據(jù)原始為經(jīng)過縮放和定標(biāo)的 digital numbers (DN)值。可以根據(jù)公式轉(zhuǎn)換為大氣層頂反射率、輻亮度、溫度等。

參考https://www.usgs.gov/land-resources/nli/landsat/using-usgs-landsat-level-1-data-product

Conversion to TOA Radiance 大氣層頂輻亮度

Landsat Level-1 數(shù)據(jù)可以通過MTL文件中的參數(shù)轉(zhuǎn)為 TOA 輻亮度：

Conversion to TOA Reflectance 大氣層頂反射率

反射波段的 DN 值可以通過MTL文件中的參數(shù)轉(zhuǎn)為 TOA 反射率:

Conversion to Top of Atmosphere Brightness Temperature 大氣層頂亮度溫度

Landsat Collection 2

(包括L1和L2級(jí)別的產(chǎn)品)

Landsat Level-2Scenes (Global)

這一級(jí)別的產(chǎn)品在大氣層頂反射率產(chǎn)品基礎(chǔ)上使用來自MODIS的水蒸氣、臭氧、氣溶膠光學(xué)厚度等輔助數(shù)據(jù)進(jìn)行了大氣校正得到地表反射率

該數(shù)據(jù)進(jìn)行了大氣校正 用戶可以直接進(jìn)入 ESPA 或者使用eEarthExplorer來提交 Surface Reflectance 處理請(qǐng)求:

ESPA: Requests submitted directly toESPArequire scenes be listed one per line within a text file (.txt). Along with Surface Reflectance processing,

ESPA 允許用戶選擇幾種附加產(chǎn)品和基本處理服務(wù):

Source products (Original input Level-1 product or metadata)
Top-of-Atmosphere Reflectance, Surface Reflectance, or Band 6 Top-of-Atmosphere Brightness Temperature products
Surface Reflectance-based Spectral Indices: NDVI, NDMI, NBR, SAVI, EVI
Customizable output options: data format, reprojection, modifying the image extents, and pixel resizing
Inter-comparison and output product statistics plotting

所有通過 ESPA 的訂單一般在 2-5 天內(nèi)處理完

Landsat Collection 2 Level-2 Science Products

Landsat Collection 2 includes the distribution of scene-based global Level-2 surface reflectance and surface temperaturescience products.包括全球L2級(jí)別的地表溫度和反射率產(chǎn)品，預(yù)計(jì)2020年早期發(fā)布

Landsat Level-2 產(chǎn)品生成于 Collection 2 Level-1 inputs that meet the <76 degrees Solar Zenith Angle constraint and include the required auxiliary data inputs to generate a scientifically viable product.

Landsat 8 OLI 地表反射率產(chǎn)品通過 Land Surface Reflectance Code (LaSRC) 算法生成(Version 1.4.1) .

Landsat 4-5 TM 和 Landsat 7 ETM+ 地表反射率產(chǎn)品通過Landsat Ecosystem Disturbance Adaptive Processing System (LEDAPS) 算法生成(Version 3.4.0).

Landsat 4-8 地表溫度產(chǎn)品通過Landsat surface temperature 算法生成 (Version 1.3.0)

Surface Reflectance

Surface reflectance (unitless) measures the fraction of incoming solar radiation that is reflected from the Earth's surface to the Landsat sensor. The LEDAPS and LaSRC surface reflectance algorithms correct for the temporally, spatially and spectrally varying scattering and absorbing effects of atmospheric gases and aerosols, which is necessary to reliably characterize the Earth’s land surface.

Visit theLandsat Surface Reflectancewebpage for additional information and documentation.

Surface Temperature

Surface Temperature measures the Earth’s surface temperature (units Kelvin) and is an important geophysical parameter in global energy balance studies and hydrologic modeling. Surface temperature is also useful for monitoring crop and vegetation health, and extreme heat events such as natural disasters (e.g., volcanic eruptions, wildfires), and urban heat island effects . A surface temperature product cannot be generated if auxiliary data is missing, although a surface reflectance product will continue to be generated.

Visit theLandsat Surface Temperaturewebpage for additional information and documentation.

Landsat Level-2 Bulk Ordering and Downloading 批量下載

TheESPA Application Programming Interface (API)使用 HTTP 交互

TheESPA Bulk Downloader

EarthExplorer: 可以提交 Surface Reflectance 單幅影像的處理請(qǐng)求

U.S. Landsat Analysis Ready Data (ARD)

U.S. Landsat ARD 包括 Top of Atmosphere (TA) reflectance, top of atmosphere Brightness Temperature (BT), Surface Reflectance (SR), Provisional Surface Temperature (ST)and Quality Assessment (QA) 數(shù)據(jù)

這些數(shù)據(jù)的一致較好，均使用逐像元太陽天頂角校正。但是 Landsat ARD 產(chǎn)品只有美國的。

U.S.Landsat Level-3 Tiles

Landsat Level-3Burned Area,Dynamic Surface Water Extent, andFractional Snow Covered Area產(chǎn)品產(chǎn)生于 U.S. Landsat Analysis Ready Data (ARD) Surface Reflectance 數(shù)據(jù)

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