Ice velocity and thickness of the world's glaciers

###Global mapping of surface ice flow velocity and ice thickness of glaciers around the world from Millan et al. (2022) The dataset presented here contains a global mapping of surface ice flow velocity and the ice thickness of glaciers around the world. Glacier surface flow velocities were calculated using *Sentinel-2/ESA*, *Landsat-8/USGS*, *Venμs/CNES-ISA*, *Pléiades/AirbusD&S* and radar data from *Sentinel-1/ESA*. *Reference and link to RGI*: The Randolph Glacier Inventory (RGI) is used to define the glacier outlines. This inventory provides global glacier outlines compiled from maps, aerial photographs and satellite images and can be found [here](https://www.glims.org/RGI/rgi60_dl.html). *Projections* : UTM (EPSG:326XX for the northern hemisphere and EPSG:327XX for the southern hemisphere) and Polar Stereographic (EPSG:3031 for Antarctica and EPSG:3414 for Greenland) Data are posted at 50 m horizontal spacing. Data are provided as geotiff `.tif` that can be opened in geographic information system. The naming convention is `VAR_RGI-X.Y_date.tif`, where: - `VAR` is the type of variable contained in the geotiff, - `RGI-X.Y` indicates the RGI region number with `X` (1 to 19) and sub-region with `Y`, and - `date` gives the date of the file generation. ###Ice velocity product Optical satellite images from [Landsat-8](https://www.usgs.gov/landsat-missions/landsat-8), [Sentinel-2](https://sentinel.esa.int/web/sentinel/missions/sentinel-2), [Venμs](https://venus.cnes.fr/fr) and synthetic aperture radar images from [Sentinel-1](https://sentinels.copernicus.eu/web/sentinel/missions/sentinel-1) were used globally to map glacier surface flow velocity in 2017 and 2018. 5 different variables (`VAR`) are provided to describe : - `V` the magnitude of the ice velocity in m/year, - `VX` the component of velocity in m/year in x direction (east-west; positive toward east), - `VY` the component of velocity in m/year in y direction (north-sourth; positive toward north), - `STDX` the standard deviation of `VX` individual measurements in m/year, and - `STDY` the standard deviation of `VY` individual measurements in m/year. No data values are set to NaN and zero for all layers. Note : the ice velocity of the ice sheets are not provided here. The ice velocity map of Antarctica can be found here https://nsidc.org/data/NSIDC-0754/versions/1 , and the ice velocity map of Greenland can be found here https://nsidc.org/data/NSIDC-0646/versions/1 ###Ice thickness product Data are posted at 50 m horizontal spacing in georeferenced geotiff format `.tiff`. 2 different variables (`VAR`) are provided to describe : - `THICKNESS` the ice thickness model in m, - `ERRTHICKNESS` the estimated error on the ice thickness model in m Note : the ice thickness of glaciers connected to the coast or ice shelves of the Antarctic ice sheet are not provided here. Thickness map for these areas can be found here https://nsidc.org/data/NSIDC-0756/versions/1 Surface reference used : access the Arctic DEM at https://www.pgc.umn.edu/data/arcticdem/ ; the ASTER GDEM v3 is available at https://search.earthdata.nasa.gov and the TanDEM-X global DEM at https://geoservice.dlr.de

### 基于Millan等人（2022）研究的全球冰川表面冰流速度与冰厚度制图数据集
本数据集包含全球范围内冰川的表面冰流速度与冰厚度制图成果。冰川表面冰流速度的计算采用了*哨兵-2号/欧洲空间局（Sentinel-2/ESA）*、*陆地卫星8号/美国地质调查局（Landsat-8/USGS）*、*Venμs/法国国家空间研究中心-ISA（Venμs/CNES-ISA）*、*Pléiades/空客防务与航天（Pléiades/AirbusD&S）*的数据，以及*哨兵-1号/欧洲空间局（Sentinel-1/ESA）*的雷达数据。

*数据集参考与伦道夫冰川目录（Randolph Glacier Inventory, RGI）链接*：本数据集采用伦道夫冰川目录（RGI）来界定冰川边界。该目录汇总了基于地图、航空照片与卫星影像编制的全球冰川边界数据，可通过[此链接](https://www.glims.org/RGI/rgi60_dl.html)获取。

*投影方式*：采用通用横轴墨卡托投影（UTM，北半球对应EPSG:326XX，南半球对应EPSG:327XX）与极方位立体投影（Polar Stereographic，南极洲对应EPSG:3031，格陵兰岛对应EPSG:3414）。数据以50米的水平分辨率发布，格式为可在地理信息系统中打开的GeoTIFF（.tif）文件。文件命名规则为`VAR_RGI-X.Y_date.tif`，各部分含义如下：
- `VAR`：代表GeoTIFF文件中包含的变量类型；
- `RGI-X.Y`：表示伦道夫冰川目录的区域编号，其中`X`取值为1至19，`Y`为子区域编号；
- `date`：代表文件生成日期。

### 冰流速度数据集
本数据集采用来自[陆地卫星8号（Landsat-8）](https://www.usgs.gov/landsat-missions/landsat-8)、[哨兵-2号（Sentinel-2）](https://sentinel.esa.int/web/sentinel/missions/sentinel-2)、[Venμs](https://venus.cnes.fr/fr)的光学卫星影像，以及来自[哨兵-1号（Sentinel-1）](https://sentinels.copernicus.eu/web/sentinel/missions/sentinel-1)的合成孔径雷达影像，完成了2017年与2018年全球冰川表面冰流速度制图。本次共提供5种不同的变量（`VAR`）用于描述冰流速度信息：
- `V`：冰流速度幅值，单位为米/年；
- `VX`：冰流速度在x方向（东西向，东向为正）的分量，单位为米/年；
- `VY`：冰流速度在y方向（南北向，北向为正）的分量，单位为米/年；
- `STDX`：`VX`单次测量值的标准差，单位为米/年；
- `STDY`：`VY`单次测量值的标准差，单位为米/年。
所有图层中的无数据值均设置为NaN与0。
注意：本数据集未提供冰盖的冰流速度数据。南极洲冰流速度图可通过https://nsidc.org/data/NSIDC-0754/versions/1 获取，格陵兰岛冰流速度图可通过https://nsidc.org/data/NSIDC-0646/versions/1 获取。

### 冰厚度数据集
数据以50米水平分辨率发布，格式为带地理参考的GeoTIFF（.tiff）文件。本次共提供2种变量（`VAR`）用于描述冰厚度信息：
- `THICKNESS`：冰厚度模型值，单位为米；
- `ERRTHICKNESS`：冰厚度模型的估算误差，单位为米。
注意：本数据集未提供与南极冰盖海岸或冰架相连的冰川的冰厚度数据。此类区域的冰厚度图可通过https://nsidc.org/data/NSIDC-0756/versions/1 获取。
本数据集采用的地表参考数据包括：北极DEM（Arctic DEM）可通过https://www.pgc.umn.edu/data/arcticdem/ 获取；ASTER GDEM v3可通过https://search.earthdata.nasa.gov 获取；TanDEM-X全球DEM可通过https://geoservice.dlr.de 获取。