The GPS antenna cable that ships with every 3DM-GX3-35 and 3DM-GX3-45 is 3 meters in length.
Cable length is important. The longer the cable, the lower the signal strength. If the user lengthens the cable, the signal strength will diminish. The loss of signal strength can only be empirically determined by trying out a particular installation. Loss of signal strength will manifest itself in the number of satellites seen, quality of data reception from satellites, etc.