AR Indoor Navigation using AR Foundation

hello..
I am working on project to create a navigation system inside buildings(indoor)..and used AR Foundation to map my physical area..
mapping process: i walked to each position in my physical area and placed an anchor for each to save all positions on cloud , After that i want to load all anchors into 2D floor plan (my physical world plan) and to do that i add each anchor position into a list and make the first anchor is a reference position on 2D Map (start mapping process at this position )and apply this code ..

Code (CSharp):

1.  
2.  
3. public void loadMap()
4.         {
5.      
6.             if (list == null)
7.             {
8.                 Debug.Log("list is empty");
9.                 return;
10.             }
11.             //  Vector3 initialPoint = cam.WorldToScreenPoint(list[0].position);
12.             Vector3 initialPoint=transform.InverseTransformPoint(list[0].position);// reference point
13.           //  Vector3 initialPoint = list[0].position;
14.             Vector3 secondPoint;
15.             Vector3 newAnc;
16.             for (int i = 1; i < list.Count; i++)
17.             {
18.               // i found the distance vector between each anchor and first anchor(reference) and then add it to the reference position in 2D map in unity scene
19.                 secondPoint = transform.InverseTransformPoint(list[i].position);//t
20.        
21.  
22.                 float x = (this.transform.position.x + (secondPoint.x- initialPoint.x));//this.transform has the same position of reference
23.                 float y = (this.transform.position.y + (secondPoint.y - initialPoint.y));
24.                 float z =100;
25.                 newAnc = new Vector3(x, y, z);
26.    
27.                 Instantiate(sphere, newAnc, Quaternion.identity);
28.        
29.             }

but always loading anchors into wrong position on 2D Map ..
and i dont know reason ..
can you solve my problem please ..
thank you