Long distance power & data transmission

I’m looking to power (and transmit data to and from) the cam from distances greater than 50 ft. How can I best boost the UART/USB/SPI to RS-485 levels? Or is there another better way to go about this?

I’ve found a few things that may help. Curious as to what anyone thinks in terms of which may work best.

  1. USB to RS-485
    http://www.robotshop.com/en/devantech-usb-rs-485-interface.html

  2. UART to RS-485
    http://www.robotshop.com/en/sfe-uart-to-rs-485-converter.html

  3. PoE possibly? The original idea for the project was to make the camera PoE-enabled, but to be honest I’m struggling mightily to accomplish this. I’ve had a few ideas, like using a PoE Network switch and then mounting an ethernet port on the board, but I’m not an experienced prototyper and don’t know how I’d do this.

I think CAN easily works over this distance and at 1 Mbit/s. For PC/host side data you could use a USB to CAN like this:

Will this take care of transferring power from the computer to the cam as well?

No, just CAN high/low and GND you still need to provide power (could hack it to find the 5V) and a transceiver chip or diodes on the cam end. This is similar to your solution, but I think it’s more reliable for longer distances and supports many nodes on the same network if you need that.