Conventional surveying, UAV photogrammetry, airborne radar surveying, which one is more cost-effective?

It depends on what you are using it for. In terms of performance, radar is the best, drones are second but the most intuitive. Conventional measurement is low-cost but time-consuming. In addition, the overall integrity is not as good as the other two methods. .

There are many types of radars, depending on your use. Drones are currently relatively cost-effective and easy to buy. Just buy a rotor drone and add a camera, and it can be operated remotely