makemaps: Generate maps of Pleistocene island extents

In g33k5p34k/PleistoDistR: Calculating Island Geomorphologies Over Pleistocene Time

Generate maps of Pleistocene island extents

Description

This function generates a series of map outputs based on the interval bins contained in the interval file (see getintervals_time() and getintervals_sealvl()). This function takes a user-supplied input bathymetry raster and generates a series of island extents based on the mean sea levels specified in the interval file. This function generates maps in three formats: ESRI shapefile format, a flat raster format (with no topography), and a topographic raster format that preserves the original bathymetric elevations of each island pixel, reprojected to the user-specified projected coordinate system.

Usage

makemaps(inputraster, epsg, intervalfile, outdir, offset = 0)

Arguments

inputraster	An input bathymetry raster in ASCII (.asc) format. Although PleistoDist should theoretically be able to use any type of ASCII-formatted bathymetry grid as input, this tool has been tested specifically with data from the General Bathymetric Chart of the Oceans (GEBCO: https://www.gebco.net). Locality-specific bathymetric maps can be downloaded from https://download.gebco.net/.
epsg	The projected coordinate system in EPSG code format. Because of the curvature of the Earth's surface, we need to apply a map projection to accurately calculate straight-line distances between points instead of using the default WGS84 geographical coordinate system. Users should specify a projected coordinate system appropriate to the geographic region being analysed using the projection's associated EPSG code (https://epsg.org/home). Geographic coordinate system projections are not recommended as those will result in distance matrices calculated in decimal degrees rather than in distance units.
intervalfile	This is the master control file generated using either the getintervals_time() or getintervals_sealvl() function. Users can also specify their own custom interval file (with nice round mean sea level values, for example) although the file will need to have a column named MeanDepth and be in CSV format.
outdir	The output directory for storing the maps generated by this function. If the specified output directory does not exist, PleistoDist will create the folder and all necessary subsidiary folders. The makemaps() function creates three folders, one containing the output maps in flat raster format (without preserving topography), one folder with maps in topographic raster format, and another folder with maps in ESRI shapefile format.
offset	A correction factor to account for constant-rate tectonic uplift or subsidence in the study area. A positive offset value results in PleistoDist assuming a constant rate of uplift from the past to the present (e.g. an offset of 1 causes the map for each subsequent interval to be corrected by subtracting 1 * TimeInterval metres from all pixel values as PleistoDist moves backward in time). A negative offset therefore forces a constant rate of subsidence from the past to the present (e.g. an offset of -1 adds 1 *TimeInterval metres to the map for each subsequent interval as PleistoDist moves backward in time). If the offset is set to the default value of 0, PleistoDist will not account for tectonic uplift or subsidence.

Value

This function generates map outputs corresponding with the sea levels specified in the interval file. Maps are generated in flat ASCII raster (without topography), topographic ASCII raster, and ESRI shapefile formats.

Examples

#create temp directory
path <- file.path(tempdir())
#load bathymetry file
fiji <- system.file("extdata","FJ.asc",package="PleistoDist")
#generate interval file for 2 intervals and 20 kya cutoff time, binning by time
getintervals_time(time=20,intervals=2,outdir=path)
#generate maps of the Fiji Archipelago with the EPSG:3141 projection,
#with default interval file and a subsidence offset of 0 m per kya
makemaps(inputraster=fiji,epsg=3141,intervalfile=paste0(path,"/intervals.csv"),
    outdir=path,offset=0)

g33k5p34k/PleistoDistR documentation built on Oct. 9, 2022, 5:27 a.m.