A still of a CNN video showing a thermal imaging captured by Ukraine, where some of the white dots show Russian landmines.CNN Ukraine is using thermal imaging and drones to find mines left by Russian forces. Ukraine's counteroffensive is being hindered by dense Russian minefields. Ukrainian soldiers showed CNN their anti-mine strategy from the trenches on the front line. Ukraine is using thermal imaging to try to locate mines that Russian forces have placed to slow, injure, and kill its troops.CNN visited frontline Ukrainian soldiers near the village of Robotine, where they were working from trenches to try to make progress against Russian forces positioned less than three miles away.In their way are dense minefields placed by Russia.The outlet filmed soldiers using a drone with a thermal camera, which clearly showed the mines, glowing, on the soldiers' screen.The mines showed up because they retain the heat from the sun while the earth cools, experts told CNN, adding that they're most visible at dawn and dusk.It's not a "precise science," but helps Ukraine see an "invisible enemy," CNN's Nick Paton Walsh, who was in the trenches with Ukraine's soldiers, said.The soldiers told CNN that after locating mines, they use special charges to blow them up so that their colleagues can move through the area.