Trying to keep an object 1.5 above the terrain at all times

I am working on unit movement for an RTS and I want to be able to keep my unit a set distance above the terrain which varies in height with hills and such. I was using a raycast from the bottom of the unit and then adjusting the height based on that. Below is the coroutine from where the function containing the height check is called:

 IEnumerator Move(GameObject Unit, float targetX, float targetZ, float targetY) 
     {
         Vector3 clickedPosition = new Vector3 (targetX, targetY + 2.5f, targetZ);
         Vector3 startPosition = transform.position;
         while(Vector3.Distance(startPosition, clickedPosition)>1f) 
         {
             transform.position=Vector3.MoveTowards(transform.position, clickedPosition, 6 * Time.deltaTime);
             HeightCheck();
             yield return null;
         }
         Debug.Log("The object has reached the destination");
     }

And here is the code for HeightCheck void HeightCheck () {

         RaycastHit hit = new RaycastHit();
         
         if (Physics.Raycast (transform.position, Vector3.down, Mathf.Infinity))
         {
             Vector3 tempPos = transform.position;
             if(hit.distance > 1.5)
             {
                 //float aboveOnePointFive = transform.position.y - hit.distance + 2.5f;
                 tempPos.y = transform.position.y - hit.distance + 2.5f;
                 Debug.Log("The distance is not right from the ground");;
             }
 
             if(hit.distance < 1.5)
             {
                 //float belowOnePointFive = transform.position.y - hit.distance + 2.5f;
                 tempPos.y = transform.position.y - hit.distance + 2.5f;
                 Debug.Log("The distance is not right from the ground");;
             }
         }
     }

This isn't working and I am unsure of why. I am also unsure if this is the most efficient way to go about doing something like this. Any help is much appreciated :)