I have done and redone the calibration and IMU reset and still get a reading of 20ft or so when sitting on the ground. I a using my vision to check vineyard drip lines and need to hover a foot or two over the vines . I need to be at six or seven feet however the display is showing 25 to 30ft. If I try and descend to the proper height, BAM, I am in the vine. How does one get an actual reading? Thanks in advance.