GVR SDK for Unity v1.130.1

I am developing applications with MirageSolo using Unity 2017.4.2 f 2.
SDK uses GoogleVRForUnity_1.130.1.
I'd like to acquire the height of the floor now but it will not work.
As an execution result, bool: True float: -1.6 is returned.
Is this my problem? Or is it a problem with SDK?
Please tell me.

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class Test : MonoBehaviour {
6.  
7.     public TextMesh text;
8.     float height;
9.  
10.     // Use this for initialization
11.     void Start () {
12.        
13.     }
14.  
15.     // Update is called once per frame
16.     void Update () {
17.  
18.         bool test = GvrHeadset.TryGetFloorHeight(ref height);
19.         text.text = "bool:" + test + "float:" + height;
20.  
21.  
22.     }
23. }
24.  

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TryGetFloorHeight

bool TryGetFloorHeight(
ref float floorHeight
)

If a floor is found, populates floorHeight with the detected height.

Otherwise, leaves the value unchanged. Returns true if value retrieval was successful, false otherwise (depends on tracking state).
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