Techniques for tracking physical assets are described. In one aspect, input indicating that an asset has been loaded on a conveyance is received. When a tag attached to the asset is unable to transmit position fix data describing a location of the asset to a server, alternative position fix data (e.g., from the conveyance or another tag coupled to another asset on the conveyance) is used to indicate the position of the asset and tag. In another aspect, a relay component is used to receive the tag position fix data from the tag and forward it to the server.