A telepresence system including an array of cameras, a user interface device and at least one processor. 02 to 4% by mass and the ratio of a straight-chain fatty acid having a carbon number of 6 to 12 in the fatty acid is 80 to 100% by mass. The coordinates are converted to cell identifiers to look up corresponding residential parcels that have been visited by the mobile devices. A receiving frequency within the prescribed frequency range of the returned COTDR signal is detected to obtain the status information.