Algorithm 1 Feature vector V_location

Input: positioning point ${\mathrm{P}}_{\mathrm{o}}({\mathrm{x}}_{\mathrm{o}},{\mathrm{y}}_{\mathrm{o}})$; collection of all scene boundaries $\mathrm{D}=\{{\mathrm{D}}_1,{\mathrm{D}}_2,\cdots ,{\mathrm{D}}_{\mathrm{n}}\}$.

Procedure: function $\mathrm{GetSceneCategory}({\mathrm{P}}_{\mathrm{o}},\mathrm{D})$

1: feature vector ${\mathrm{V}}_{\mathrm{location}}\leftarrow {\{0\}}^{{\mathrm{N}}_{\mathrm{category}}+1}$

2: For each scene ${\mathrm{D}}_{\mathrm{i}}=\{{\mathrm{T}}_1,{\mathrm{T}}_2,\cdots \}$ in collection D

3:  For each polygon ${\mathrm{T}}_{\mathrm{i}}=[({\mathrm{x}}_1,{\mathrm{y}}_1),({\mathrm{x}}_2,{\mathrm{y}}_2),\cdots ,({\mathrm{x}}_{\mathrm{n}},{\mathrm{y}}_{\mathrm{n}}),({\mathrm{x}}_1,{\mathrm{y}}_1)]$ in ${\mathrm{D}}_{\mathrm{i}}$

4:   For each pair of sequential points ${\mathrm{P}}_{\mathrm{i}},{\mathrm{P}}_{\mathrm{i}+1}$ in ${\mathrm{T}}_{\mathrm{i}}$

5:    calculate the angle ${\mathsf{\theta }}_{\mathrm{i}}$ between $\overrightarrow{{\mathrm{P}}_{\mathrm{o}}{\mathrm{P}}_{\mathrm{i}}}$ and $\overrightarrow{{\mathrm{P}}_{\mathrm{o}}{\mathrm{P}}_{\mathrm{i}+1}}$

6:    sum up angles ${\mathsf{\theta }}_{\mathrm{Sum}}\leftarrow {\mathsf{\theta }}_{\mathrm{Sum}}+{\mathsf{\theta }}_{\mathrm{i}}$

7:   End For

8:   If ${\mathrm{T}}_{\mathrm{i}}$ is the outer boundary and ${\mathsf{\theta }}_{\mathrm{Sum}}$ equals 2π

9:    element ${\mathrm{V}}_{\mathrm{k}}\leftarrow 1$ in feature vector ${\mathrm{V}}_{\mathrm{location}}$, where k represents the category of scene ${\mathrm{D}}_{\mathrm{i}}$

10:   Else If ${\mathrm{T}}_{\mathrm{i}}$ is the inner boundary and ${\mathsf{\theta }}_{\mathrm{Sum}}$ equals 2π

11:    element ${\mathrm{V}}_{\mathrm{k}}\leftarrow 0$ in feature vector ${\mathrm{V}}_{\mathrm{location}}$, where k is the category of scene ${\mathrm{D}}_{\mathrm{i}}$

12:   End If

13:   End For

14: End For

15: If elements of feature vector ${\mathrm{V}}_{\mathrm{location}}$ all equal to 0

16:  element ${\mathrm{V}}_0\leftarrow 0$ in feature vector ${\mathrm{V}}_{\mathrm{location}}$, means the point locates outside all the scenes

17: End If

Output: feature vector ${\mathrm{V}}_{\mathrm{location}}$