Convert lines to transects (strips)

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Description

Convert lines (center) with transect widths to strips and compute rotation angle from vertical. With the intersect function in gpclib, it also now clips the portions of the transects that are outside the study area.

Usage

1
lines_to_strips(lines, study.area, width = NULL)

Arguments

lines

dataframe with fields named label,x0,x1,y0,y1 and optionally width

study.area

owin class giving study area window

width

optional; if all lines have the same width it can be specified here

Details

The function assumes that the intersection of the strip and the study area only results in a single intersection polygon. That means the entire strip cannot pass outside the study area and then come back into the study area as in an aerial transect that passes over water to over land and then back over water. In this case, the line should end when it passes out of the sampled area and restarted when back in the sampled area.

Value

lines

a psp class of lines with label and angles for rotation added

transects

a list of dataframes with polygon coordinates

Author(s)

Jeff Laake

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