You can only change the minimap image to a static image, by importing it under specific name (I think it's war3mapMap.blp)
I did a radar like this once. I disabled minimap display of all units in map, aside from a special, invisible, dummy unit. Then I created a line of these units and rotated it around the center of the map. All "detected" units were displayed using pings. That's the only way I could think of.