Some primary concerns with freehand 3D ultrasound are time-consuming calibration operations, overall accuracy, and computation time during the 3D reconstruction process. A procedure was developed to reduce the calibration time to only 10 seconds by planning the path of the probe. A decrease in marginal error may improve the overall accuracy by searching axial and lateral distances with a maximum correlation coefficient, and was based on constructing an adaptive decorrelation curve from images containing Rayleigh and coherent scatters. Marginal errors were reduced in the range of 3% to 11% when the distance estimation was between 0.15mm and 0.375mm in in-vitro studies. To save computation time within the 3D reconstruction, a low-resolution 3D reconstruction algorithm is proposed so that verification can be completed prior to computing a high-resolution reconstruction.