To give you an advice, I would need to know what real environment you have; what types and sizes of obstacles, etc.
If the wireless modules are specified to transmit over 500 M over line of sight, including antennas, then they often can do it also without LOS.
You possibly can consider using more directive antennas, and locating them so that the RF signal can reflect from a building, etc., to get through.
To cover 500 M, it may be easy to locate the transmitter and receiver with antennas to places with LOS or such that the RF signal can pass. Then you will need only DC and data lines longer from your "base" which may be easier to install.
Most wireless modules at 915 MHz promise several mile range with < 1 W RF power, at 2.45 GHz, 0.1 W is often OK, at 5.8 GHz, even less. Using good antennas and terrain survey is the secret of a successful transmission. Be ready to experiment!