survey.design: Generate Survey Sampling Stations

In TobieSurette/gulf.spatial: DFO Gulf Region Spatial Functions

Generate Survey Sampling Stations

Description

Returns a set of randomly-selected snow crab survey sampling stations. Each station is drawn from a square grid, a lattice which overlays the survey area. Longitude and latitude coordinates of the survey polygon's vertices are converted to UTM coordinates (NAD83). A square grid lattice is overlaid over the survey area. The dimensions of the grid vary according to number of required sampling stations and the area of the survey polygon.

Usage

scs(n, longitude, latitude, hole = NULL, alternates = 0, grids = FALSE)

nss(n, alternates = 0, stations, type)

Arguments

n	Integer specifying the desired number of sampling stations.
longitude, latitude	Numeric vector specifying, in decimal degrees, the longitude coordinate of each vertex of the survey polygon, which specifies the survey area. Multiple, disjoint polygons may be separated by NA values. If not specified, then the snow crab survey polygon is used.
hole	Logical vector. When multiple polygons are specified in longitude and latitude, then hole may be used to specify if some are ‘holes’. The length of hole may be the length of the coordinate vectors or the number of polygons defined within them.
alternates	Integer specifying the number of additional, alternate sampling stations per grid to be generated. The default value is zero.
grids	Logical value specifying whether the grid coordinates are to be included in the output for the snow crab survey. Alternatively, the output from a previous call of scs may be used. Specifically, the grid definitions specified in the grids element of the output is used to generate points within each element. Alternately, if the complete of grids which overlay the sGSL survey area is dersired, set grids = ‘complete’ or‘all’. The default value is FALSE.
stations	Data frame specifying the set of survey stations to be sampled.
type	Character string specifying the 'type' label to be assigned in the resulting sample.

Value

If grids is FALSE, a data frame is returned with sampling station coordinates (longitude and latitude), the station type (whether the station is a primary or alternate station) and a grid label which identifies from which grid the sample was drawn.

If grids is TRUE, then a two-element list is returned. The first element contains the station table described above, while the second element contains a list defining the coordinates of each grid vertex as well as the grid label.

Functions

• scs(): Snow crab survey station design.

• nss(): Northumberland Strait survey station design.

Examples

# Snow crab survey:
x <- scs(355) # Generate 355 survey stations.
x <- scs(355, alternates = 2) # Include 2 alternate station in the output.
x <- scs(355, alternates = 2, grids = TRUE) # Include grids in the export.

# Northumberland Strait survey:
x <- nss(100) # Generate 100 survey stations.
x <- nss(80, alternates = 2) # Generate 80 x survey stations plus 2 alternates sets

TobieSurette/gulf.spatial documentation built on Sept. 26, 2024, 7:41 p.m.