Page 160 - ITU Journal Future and evolving technologies – Volume 2 (2021), Issue 2

ITU Journal on Future and Evolving Technologies, Volume 2 (2021), Issue 2

Algorithm 1 Extraction of shape features of the target.
1: procedure SHAPE‑FEATURES‑EXTRACTION
th
th
2: % Consider that we are at laser mesh at the steering position (see Fig. 5), and each intersection of the laser beams are unique
in the ( , , ) coordinate plane
3: for = − ∶ do
4: for = 1 ∶ do
5: if there is blockage at an intersection of the laser beams at ( , , ) detected using / < at respective RXs then
G
6: Assign area ( , , ) to each blocked laser mesh intersection position as shown in Fig. 5(b)
7: if blockage at same ( , ) position at different mesh then

8: Extend a 3D area using length (where = Δ ) across the mesh where the blocked positions have the same
e
e
( , ). Label this 3D area as the central section as shown in Fig. 6
9: After a central section has been identi ied, the area on the sides of it (i.e. different values) is labeled as wings
section (discussed in Section 4)
th
10: if the area of the wings decreases more than or equal to half at a later mesh then
11: It is identi ied as the tail section.
w
12: The 3D area of wings and tail section is obtained by extending the 2D area of the plane shown in Fig. 6 by ,
e
t
and , respectively, on both sides of the plane.
e
13: The 3D area for wings and tails is extended to later mesh, only if later mesh positions have same ( , ) coor‑
dinates
14: end if
15: end if
16: end if
17: end for
18: end for
19: return Estimated shape features of the target section‑wise (if the target is detected)
20: end procedure
2
of two beams) is represented as ( , , ) = ( , , ), is formed shown in Fig. 6. The length of the central sec‑

where is one edge of the squares shown in Fig. 5(b). An tion between any two laser meshes is = Δ given at
e
example blockage of four neighboring intersections, their line 8. After the central section has been identi ied, any
corresponding areas, and area of elements are illustrated laser mesh intersections that are blocked and not part of
in Fig. 5(b), where ≈ Δ (see Fig. 2). There is a single the central section and extend along the or ‑axes only
blocked intersection at = 1 laser mesh, whereas, ive is considered either as a wing or tail section. The 3D area
and three blocked intersections at = 2 and = 3, re‑ and lengths of the wings and tail sections are provided at
spectively. A 3D area of the target based on the blocked lines 9 to 13 of Algorithm 1.
laser beams at = 1, 2, 3 can be approximately calculated The 3D shape of a target can have a minimum of one sec‑
(Fig. 6). The overall procedure for 3D area calculation and tion and a maximum of three sections. These are cen‑
extraction of shape features of the target are given in Al‑ tral, wing, and tail sections as shown in Fig. 6. The to‑
gorithm 1. tal length of the central section of a target is given as
c
c
(c) = × ( − 1), where = Δ , and is the num‑
B
e
e
B
At lines 2, and 3 of Algorithm 1, we traverse over all the ber of meshes that have a blocked beam or beams. Four
steering positions and laser mesh at these steering posi‑
th
tions. We will focus on the steering position and cor‑ shape categories recognizable by the proposed method
responding = 1, 2, 3, laser mesh, shown in Fig. 5 for the are shown in Fig. 7. The width of the central section at
(c)
(c)
(c)
th
explanation of the algorithm. At lines 5 and 6, if there is a the mesh is = × ,B , where ,B are the num‑
blockage due to the presence of a target and the condition ber of the blocked laser beams at the center section of the
th
/ < is true (see Section 3.2), a ixed area ( , , ) mesh. The coordinates of the blocked positions at the
G
th
is assigned to each blocked laser mesh intersection posi‑ mesh constituting the width of the central section are
(c)
(c)
(c)
(c)
(c)
tion. The area assignment due to blockage is shown in ( , , ), where , and ,o are the constant coor‑
,o

,o
,o
Fig. 5(b). On line 7 it is checked whether the blockage dinates in the and planes, respectively, whereas (c)

is present at same points in the plane at different th varies. The height of the central section at the mesh
th
laser mesh. To understand that, consider that we have is obtained similarly as ℎ (c) = × (c) . The coordinates

blockages at the same points in the plane at = 1, 2, 3, of the blocked positions at the th ,B
laser mesh shown in Fig. 5(a) and (b), then we can draw mesh contributing to
(c)
(c)
(c)
a straight line passing through these points (along the ‑ the height of the central section are ( , , ) where

,o
,o
(c)
axis) at = 1, 2, 3, laser mesh and the line will be per‑ only varies and the other two coordinate values are
pendicular to the laser mesh plane. If instead of a line, constant. The width and height of the central section are
we consider blockage area ( , , ) extension across the shown in Fig. 6 for a particular target and in Fig. 7 for dif‑
laser mesh positions along the ‑axis, a 3D central section ferent categories of the targets. In Fig. 6, the length, width,
146 © International Telecommunication Union, 2021