Depending on what options you have in your van, your shark fin antenna on top of your van can have multiple features built into it. On my van, I have qty = 3, shark fin antennas mounted on top of the front of the van. My antennas are 3-in-1 antennas: 3G/4G-LTE cellular, 2.4 & 5Ghz WiFi, and active 1575 Mhz GPS.
Shark fin antennas require a large circle around them, often up to 42" in diameter in order to create the proper ground plane to achieve the best reception.
Many people that are dependent on using the cellular or GPS antennas often have to raise the antenna up to the plane of the solar panels or roof rack in order to get good antenna reception.
On my van, my original antenna, was a 2-in-1 antenna: GPS and 4G.