Goniometry is the science of radio direction finding. All electromagnetic energy has polarity, and that polarity can be detected. The funny-looking antenna on the truck right there is designed to detect the compass bearing of radio energy sources. When Americans arrived in France during 1917, the French introduced them to the technologies and systems they had already developed. Unsatisfied to simply learn the French way, which included a sort of mobile home-radio station, the doughboys put their all-American love of motor vehicle tinkering to use and invented the signals intelligence truck.
That is, of course, a truck up there. No red-blooded American would think to call it a “tractor.” Nevertheless, American farm boys were still calling all vehicles larger than a motorcar “tractors” at the time, since traction was their primary purpose. Wheels left this system road-bound but that was acceptable in France, where roads were still relatively modern compared to American ones at the time. What mattered is that an operator could drive the “gonio tractor” to a convenient point, use the equipment in place, report what they learned with their own radio, and then move to a new location.
I doubt they used an internal generator. There is probably a towed electric generator out of frame, with a chase vehicle to pull it, or to help dig this monster out of French mud. The windows are painted over to remove glare and keep out spying eyes, so I imagine there is electric lighting inside. I don’t know about air conditioning, but the funny-looking roof might have sliding or shuttered covers to set up/break down the antenna and let a breeze inside. Although they broke down and got stuck as often as one might expect, at least three of these vehicles did important service during the Second Battle of the Marne, which broke the back of the German army.
Americans motorized tactical SIGINT. Future generations of US Army vehicles ended up in the same role. I have written a post about this topic before. It is linked below. Compare the “gonio tractor” to the Jeep-mounted and Humvee-mounted systems below. All of them were built to do essentially the same job, one that the Army has almost always done well.
