@conference {, title = {Testing an Ultrasonic Local Positioning System for 3D Spaces}, booktitle = {International Conference on Indoor Positioning and Indoor Navigation (IPIN 2018).}, year = {2018}, month = {09/2018}, pages = {1-4}, publisher = {IPIN}, organization = {IPIN}, address = {Nantes, Francia}, author = {K. Mannay and Ure{\~n}a, J. and A. Hernandez and J. M. Villadangos} }