Algorithm 1 BIB algorithm.
Input: Region R, threshold T, the four coordinates $(x_A,y_A)$, $(x_B,y_B)$, $(x_C,y_C)$, and $(x_D,y_D)$, and the four sensor values $f_A$, $f_B$, $f_C$, and $f_D$ of all $S_i$, the heights and the widths of all $S_i$
Output:${\widehat{C}}_T$
1:	for$i\leftarrow 1,m$do
2:	$S\leftarrow S_i$.
3:	Calculate $a_{11}$, $a_{10}$, $a_{01}$, and $a_{00}$ with reference to S.
4:	if $a_{11}\ne 0$ then
5:	$\widehat{u}\leftarrow u+\frac{a_{01}}{a_{11}}$
6:	$\widehat{v}\leftarrow v+\frac{a_{10}}{a_{11}}$
7:	$Q\leftarrow \frac{a_{00}{a}_{11}-a_{01}{a}_{10}}{a_{11}}$
8:	$E\leftarrow \frac{T-Q}{a_{11}}$
9:	Calculate $H_E(\widehat{A})$, $H_E(\widehat{B})$, $H_E(\widehat{C})$, $H_E(\widehat{D})$.
10:	$S^{\prime }\leftarrow H_E(\widehat{A})-H_E(\widehat{B})+H_E(\widehat{C})-H_E(\widehat{D})$.
11:	if $a_{11}>0$ then
12:	$\left|{\widehat{S}}_T\right|\leftarrow W·H·\left|S^{\prime }\right|$
13:	else
14:	$\left|{\widehat{S}}_T\right|\leftarrow W·H·(1-\left|S^{\prime }\right|)$
15:	end if
16:	else
17:	$U\leftarrow \left\{\right\}$
18:	for $j\leftarrow [A,\overline{AB},B,\overline{BC},C,\overline{CD},D,\overline{DA}]$ do
19:	if j in $[A,B,C,D]$ then
20:	if $\widehat{f}(u_j,v_j)\ge T$ then
21:	Add j to U.
22:	end if
23:	end if
24:	if j in $[\overline{AB},\overline{BC},\overline{CD},\overline{DA}]$ then
25:	if j is intersected with the line $\widehat{f}(u,v)=T$ then
26:	Add the intersection to the ordered set U.
27:	end if
28:	end if
29:	end for
30:	if $U=⌀$, $|{\widehat{S}}_T|=0$ then
31:	$|{\widehat{S}}_T|\leftarrow 0$
32:	else
33:	$|{\widehat{S}}_T|$ is equal to the area of the polygon of which the vertexes are listed in set U.
34:	end if
35:	end if
36:	$\left|{\widehat{S}}_{Ti}\right|\leftarrow \left|{\widehat{S}}_T\right|$
37:	end for
38:	${\widehat{C}}_T\leftarrow \frac{1}{\left|R\right|}·{\displaystyle \sum _{i=1}^m}\left|{\widehat{S}}_{Ti}\right|$