eBook: R-scripts for Generation of 5, 8 and 16 Random Sampling Points

The Global Geochemical Reference Network consists in total of 19,833 grid cells of 160x160 km that cover the whole globe. The land surface of the Earth is covered by 7356 grid cells (Global Terrestrial Network, GTN), and the marine surface by 12,477 grid cells (Global Marine Network, GMN). Planning the sampling campaigns in both realms requires the generation of random sampling points within each of the 160x160 km grid cell. For this purpose, three R-scripts are made available for the generation of 5-, 8- and 16-random sampling points within each 160x160 km grid cell. The three R-scripts can be used to generate random sampling points within any other size rectangular grid cell. The following publication provides the R-scripts, instructions for their use, and the format of the input and output files:

 

He, J. & Geng, X., 2022. R-scripts for Generation of 5, 8 and 16 Random Sampling Points Within Predefined Rectangles. IUGS Commission on Global Geochemical Baselines, Athens, Hellenic Republic, Special Publication, 3, vi, 14 pp., 5 Figures, 3 Appendices, Supplementary material, ISBN: 978-618-85049-2-9;

https://doi.org/10.5281/zenodo.7307202. 

 

Supplementary material

 

The following files can be downloaded from different web pages of the IUGS Commission on Global Geochemical Baselines: -

 

(a) Executable R-scripts:

• randomSampling5PointsOnGrids.R (R script for the generation of 5 random points).
• randomSampling8PointsOnGrids.R (R script for the generation of 8 random points).
• randomSampling16PointsOnGrids.R (R script for the generation of 16 random points).

The source code of the 5, 8 and 16 random sampling points are in Appendices 1, 2 and 3, respectively.

The three executable R-scripts for the generation of 5-, 8- and 16-random points in predefined rectangles over the terrestrial and marine surfaces are in a zip file:

‘IUGS-CGGB_R-scripts_Generation_5-8-16_random_points.zip’, which can be downloaded from the ‘Publications/Software Programs’ web page.

 

(b) Global Reference Network grid cells of 160x160 km files:

• IUGS-CGGB_19833_GRN_160x160km_grid_cells.xlsx (Microsoft™ Excel workbook file with the 19,833 grid cells of the Global Reference Network each of 160x160 km).
• IUGS-CGGB_GRN_19833_160x160km_grid_cells.zip (same as above but in a Google Earth kml file format). When unzipped the file name is: IUGS-CGGB_19833_GRN_160x160km_grid_cells.kml.

The above two files can be downloaded from the ‘Sampling/GTN 160x160 km’ web page.

 

(c) Global Terrestrial Network grid cells of 160x160 km files: 

• IUGS-CGGB_7356_GTN_160x160km_grid_cells.xlsx (Microsoft™ Excel workbook file with the 7356 grid cells of the Global Terrestrial Network each of 160x160 km).
• IUGS-CGGB_7356_GTN_grid_cells_160x160km.zip (same as above but in a Google Earth kml file format). When unzipped the file name is: IUGS-CGGB_7356_GTN_grid_cells_160x160km.kml.

The above two files can be downloaded from the ‘Sampling/GTN 160x160 km’ web page.

 

(d) Randomly selected sampling points in each Global Terrestrial Network grid cell of 160x160 km files:

• IUGS-CGGB_5-random-points_per_GTN_160x160km-grid-cell.xlsx (Microsoft™ Excel workbook file with 5 random points in each of the 7356 grid cells of 160x160 km totalling 36,780 random sampling points).
• IUGS-CGGB_5-random-points_per_GTN_160x160km-grid-cell.zip (same as above but in a Google Earth kml file format). When unzipped the file name is: IUGS-CGGB_5-random-points_per_GTN_160x160km-grid-cell.kml.
• IUGS-CGGB_8-random-points_per_GTN_160x160km-grid-cell.xlsx (Microsoft™ Excel workbook file with 8 random points in each of the 7356 grid cells of 160x160 km totalling 58,848 random sampling points).
• IUGS-CGGB_8-random-points_per_GTN_160x160km-grid-cell.zip (same as above but in a Google Earth kml file format). When unzipped the file name is: IUGS-CGGB_8-random-points_per_GTN_160x160km-grid-cell.kml.
• IUGS-CGGB_16-random-points_per_GTN_160x160km-grid-cell.xlsx (Microsoft™ Excel workbook file with 16 random points in each of the 7356 grid cells of 160x160 km totalling 117,696 random sampling points). It is noted that this sampling density is not recommended for the Global Geochemical Reference Network.
• IUGS-CGGB_16-random-points_per_GTN_160x160km-grid-cell.zip (same as above but in a Google Earth kml file format). When unzipped the file name is: IUGS-CGGB_16-random-points_per_GTN_160x160km-grid-cell.kml.

The above six files can be downloaded from the ‘Sampling/Sampling Design’ web page.

 

 (e) Global Marine Network grid cells of 160x160 km:

• IUGS-CGGB_12477_GMN_160X160km_grid_cells.xlsx (Microsoft™ Excel workbook file with the 12,477 grid cells of the Global Marine Network each of 160x160 km).
• IUGS-CGGB_12477_GMN_160x160km_grid_cells.zip (same as above but in a Google Earth kml file format. When unzipped the file name is: IUGS-CGGB_12477_GMN_160x160km_grid_cells.kml).

The above two files can be downloaded from the ‘Sampling/GMN 160 x 160 km’ web page.

 

The following files are necessary for the planning of the Global Marine Network random sampling campaign:

• IUGS-CGGB_19833_GRN_160x160km_grid_cells.xlsx (File is the same as in (b)).
• IUGS-CGGB_19833_GRN_160x160km_grid_cells.zip (File is the same as in (b)).
• IUGS-CGGB_7356_GTN_160x160km_grid_cells.xlsx (File is the same as in (c)).
• IUGS-CGGB_7356_GTN_grid_cells_160x160km.zip (File is the same as in (c)).
• IUGS-CGGB_5-random-points_per_GTN_160x160km-grid-cell.xlsx (File is the same as in (d)).
• IUGS-CGGB_5-random-points_per_GTN_160x160km-grid-cell.zip (File is the same as in (d)).
• IUGS-CGGB_8-random-points_per_GTN_160x160km-grid-cell.xlsx (File is the same as in (d)).
• IUGS-CGGB_8-random-points_per_GTN_160x160km-grid-cell.zip (File is the same as in (d)).

The reason that the Global Terrestrial Network files are required for the planning of the Global Marine Network random sampling is pictorially explained in the following two figures. The left hand side figure shows the five random sampling points in the marine realm, and the right hand figure the five random sites within the 160x160 km grid cells of both the marine and terrestrial parts. It is obvious from these two figures that some of the random sampling points in coastal GTN grid cells fall in the sea (or water bodies in general). As these coastal GTN grid cells are not in the GMN database, the only way to have a complete set of random sampling points in the marine real is to plot on the same map the two databases.

 

 

 

 

 

 

 

 

 

 

 

 

(f) Randomly selected sampling points in each Global Marine Network grid cell of 160x160 km:

• IUGS-CGGB_5-random-points_per_GMN_160x160km-grid-cell.xlsx (Microsoft™ Excel workbook file with 5 random points in each of the 12,477 grid cells of 160x160 km totalling 62,385 random sampling points).
• IUGS-CGGB_8-random-points_per_GMN_160x160km-grid-cell.xlsx (Microsoft™ Excel workbook file with 8 random points in each of the 12,477 grid cells of 160x160 km totalling 99,816 random sampling points).

The above two files can be downloaded from the ‘Sampling/GMN 160 x 160 km’ web page.