You can save the turtle's current heading, turn it 90-degrees left and see what's on the left side of the original heading with
scan x 180
then turn it 90-degrees right from original heading and see what's on the right side of the original heading with
scan x 180
then turn it back to its original heading.
Here's code that illustrates this. Set the scan angle to something smaller than 180 to see more clearly what's happening. As you step through the go step it rotates and highlights what it is seeing.
globals [ scan-angle]
turtles-own [ actual-heading ]
to setup
clear-all
set scan-angle 180
create-turtles 1 [ set size 4 set heading 0 set actual-heading heading]
reset-ticks
end
to go
ask turtle 0 [ set heading (heading + 30) set actual-heading heading]
scansides scan-angle
tick
end
to scansides [ angle ]
ask patches [ set pcolor black]
ask turtle 0
[
;; scan left side
set heading (actual-heading - 90)
ask patches in-cone 10 angle [ set pcolor red]
;; scan right side
set heading (actual-heading + 90)
ask patches in-cone 10 angle [ set pcolor green]
set heading actual-heading
]
end