Standardize formatting and file names (#12)

Always use "location-type" for the file and folder names to be
consistent. Includes the information from individual folder README.md
files in the main README instead to make it more accessible. Add a
preview figure to each folder to make it easier to inspect without
having to open the notebooks. Clarify the license information.

README.md

@@ -1,33 +1,113 @@
 # Curated collection of open geophysics data for tutorials and documentation
 
-This is a place to format and prepare public open-licensed datasets for
-use in our tutorials and documentation. 
+This is a place to format and prepare public **open-licensed** datasets for
+use in our tutorials and documentation.
+
 We include the source code that prepares the datasets for redistribution
 by filtering, standardizing, converting coordinates, compressing, etc.
-The goals is to make loading the data as easy as possible (e.g., a single
+The goal is to make loading the data as easy as possible (e.g., a single
 call to `pandas.read_csv` or `xarray.load_dataset`).
-When possible, the code also downloads the original data (otherwise the
+Whenever possible, the code also downloads the original data (otherwise the
 original data are included in this repository).
 
-The curated datasets will be published in a Zenodo or figshare archive
-and downloaded with Pooch in tutorial notebooks and source code.
+The curated datasets are published in a Zenodo archive:
+https://doi.org/10.5281/zenodo.5167357
+
+## Datasets
+
+| File name | Size | Hashes |
+|:----------|:-----|:-------|
+| `alps-gps-velocity.csv.xz` | 0.005 Mb | `md5:195ee3d88783ce01b6190c2af89f2b14` `sha256:77f2907c2a019366e5f85de5aafcab2d0e90cc2c378171468a7705cab9938584` |
+| `britain-magnetic.csv.xz` | 2.7 Mb | `md5:8dbbda02c7e74f63adc461909358f056` `sha256:4e00894c2e0fa5b9c547719c8ac08adb6e788a7074c0dae9fb1b2767cf494b38` |
+| `british-columbia-lidar.csv.xz` | 4.4 Mb | `md5:354c725a95036bd8340bc14e043ece5a` `sha256:03c6f1b99374b8c00c424c788cb6956bc00ab477244bb69835d4171312714fe1` |
+| `caribbean-bathymetry.csv.xz` | 7.8 Mb | `md5:a7332aa6e69c77d49d7fb54b764caa82` `sha256:9adaa2ead1cd354206235105489b511c4c46833b2e137a3eadc917243d16f09e` |
+| `earth-gravity-10arcmin.nc` | 2.5 Mb | `md5:56df20e0e67e28ebe4739a2f0357c4a6` `sha256:d55134501da0d984f318c0f92e1a15a8472176ec7babde5edfdb58855190273e` |
+| `earth-geoid-10arcmin.nc` | 1.3 Mb | `md5:39b97344e704eb68fa381df2eb47da0f` `sha256:e98dd544c8b4b8e5f11d1a316684dfbc2612e2860af07b946df46ed9f782a0f6` |
+| `earth-topography-10arcmin.nc` | 2.7 Mb | `md5:c43b61322e03669c4313ba3d9a58028d` `sha256:e45628a3f559ec600a4003587a2b575402d22986651ee48806930aa909af4cf6` |
+| `southern-africa-gravity.csv.xz` | 0.14 Mb | `md5:1dee324a14e647855366d6eb01a1ef35` `sha256:f5f8e5eb6cd97f104fbb739cf389113cbf28ca8ee003043fab720a0fa7262cac` |
+
+### GPS velocities for the Alpine region
+
+This is a compilation of 3D GPS velocities for the Alps.
+The horizontal velocities are reference to the Eurasian frame.
+All velocity components and even the position have error estimates,
+which is very useful and rare to find in a lot of datasets.
+
+* Original source: [Sánchez et al. (2018)](https://doi.org/10.1594/PANGAEA.886889)
+* Original license: CC-BY
+
+### Airborne magnetic survey of Britain
+
+This is a digitized version of an airborne magnetic survey of Britain.
+Contains British Geological Survey materials © UKRI 2021.
+
+* Original source: [British Geological Survey](https://www.bgs.ac.uk/datasets/gb-aeromagnetic-survey/)
+* Original license: Open Government Licence
+
+### LiDAR point cloud of the Trail Islands in British Columbia, Canada
+
+This is a point cloud sliced to the small
+[Trail Islands](https://apps.gov.bc.ca/pub/bcgnws/names/21973.html) North of
+Vancouver to reduce the data size.
+The islands have some nice looking topography and their isolated nature creates
+problems for some interpolation methods.
+
+* Original source: [LidarBC](https://www2.gov.bc.ca/gov/content/data/geographic-data-services/lidarbc)
+* Original license: Open Government Licence - British Columbia
+
+### Single-beam bathymetry of the Caribbean
+
+This dataset is a compilation of several single-beam bathymetry surveys.
+The data are originally in MGD77 format and include a header with metadata on
+each survey (`MGD77_921744.h77t`).
+The original data file was compressed with LZMA to save space and make it
+possible to upload it to this GitHub repository.
+
+* Original source: [NOAA NCEI](https://ngdc.noaa.gov/mgg/geodas/trackline.html)
+* Original license: Public domain
+
+### Global gravity, geoid height, and topography grids
+
+This dataset includes global 10 arc-minute resolution grids of
+gravity acceleration (gravitational and centrifugal), geoid height,
+and topography/bathymetry.
+
+* Original source: [EIGEN-6C4](https://doi.org/10.5880/icgem.2015.1) (gravity
+  and geoid) and [ETOPO1](https://doi.org/10.7289/V5C8276M) ice surface
+  (topography) generated by the
+  [ICGEM calculation service](http://icgem.gfz-potsdam.de/home)
+* Original license: CC-BY (EIGEN-6C4) and public domain (ETOPO1)
+
+### Ground gravity of Southern Africa
+
+This is a public domain compilation of ground measurements of gravity from
+Southern Africa.
+The horizontal datum is not specified and heights are referenced to "sea
+level", which we will interpret as the geoid (which realization is likely not
+relevant since the uncertainty in the height is probably larger than geoid
+model differences).
+Heights were not converted to geometric since that can be done in tutorials for
+better educational purposes.
+
+* Original source:[NOAA NCEI](https://www.ngdc.noaa.gov/)
+* Original license: Public domain
 
 ## Requirements for included datasets
 
 All source datasets must:
 
-1. Be either in the public domain or distributed under a permissive licence 
-   (e.g. CC-BY but not CC-BY-NC).    
+1. Be either in the public domain or distributed under a permissive licence
+   (e.g. CC-BY but not CC-BY-NC).
 1. Represent a common real-world application.
-1. Contain interesting features that lead to teachable moments for tutorials 
-   (e.g., interesting anomalies easily associated with geology, large gaps in 
+1. Contain interesting features that lead to teachable moments for tutorials
+   (e.g., interesting anomalies easily associated with geology, large gaps in
    bathymetry lead to interesting interpolation issues, etc).
 
-The curated output data should:
+The output datasets should:
 
 1. Contain standard and descriptive variable names ("longitude" instead of
    "LON", "gravity_disturbance_mgal" instead of "FAA")
-1. Include associated metadata (datum, license, source, etc.) if supported 
+1. Include associated metadata (datum, license, source, etc.) if supported
    by the format (e.g. netCDF following CF conventions, but not CSV).
 3. Specify units through appropriate metadata (CF conventions in netCDF or
    column names in CSV, like `gravity_disturbance_mgal`). Exceptions are
@@ -39,7 +119,11 @@ The curated output data should:
 
 ## License
 
-See individual data files or the notebooks that process them for the respective
-licenses. Unless otherwise noted, our output data are licensed CC-BY.
+All Python source code is made available under the BSD 3-clause license. You
+can freely use and modify the code, without warranty, so long as you provide
+attribution to the authors.
 
-All source code is available under the BSD 3-clause license.
+Unless otherwise specified, all data files and figures created by the code are
+available under the Creative Commons Attribution 4.0 License (CC-BY).
+The licenses for the original source data are specified in this `README.md`
+file and the Jupyter notebooks.