Algorithm 1: TGHM Exploration Algorithm
Input: Laser data X generated by LIDAR; Odometer data O generated by the mobile robot;
Process:
1:	Initialize the topology node set Tt with the origin position P0: T0 = {P0};
2:	Initialize the grid map M according to X and O and the topology map T according to T0;
3:	Initialize the candidate target point set C0, the candidate topology node set N0: C0, N0 = ∅;
4:	Initialize t as the round number of the exploration: t = 1;
5:	repeat
6:	Update Ct with candidate target points generated by geometry rules;
7:	if Ct ≠ ∅
8:	Update Nt with filtered candidate target points meet from Ct:Nt = Nt−1 ∪ Ct;
9:	Filter the candidate topology nodes according to Equations (10) and (11):      Nt = Nt\{Nt}unqualified;
10:	else
11:	Nt = Nt−1;
12:	end if
13:	if Nt ≠ ∅
14:	Choose the node with the highest value from Nt by Equation (9) as the next target point Pt;
15:	else
16:	The exploration finishes: return M and T;
17:	end if
18:	Motivate the robot towards Pt and update M according to Xt and Ot;
19:	Turn Pt into a topology node and update Tt accordingly: Tt = Tt−1 ∪ {Pt}, Nt = Nt\{Pt};
20:	Update the topology map T with Tt;
21:	t = t + 1;
22:	until return called
Output: The established map M and the topology map T;