To reach this tower, you have to make it to the top of the parking building southeast of the tower marker in the map. From there, climb up the ledge near the tower so you can drop down to the ledge below. Climb up the ladder nearby to reach the tower perimeter. The switch console for the gate is located inside the building.
First, you have to find the other switch console. Follow the signal on foot and you'll find it in the side of the building. Once that's unlocked, backtrack and hack the security router to get a camera feed inside the room. Switch to the laptop camera to see the switch console. Unlock it to gain access to the tower.
This tower is located on top of a residential building. Before going there, open your Profiler to immediately see where the signal is leading. You should find the switch console at ground level. Now, find the scissor lift beside a building to the south and ride it up.
Make your way to the rooftop where you'll find the now unlocked security gate. Go inside and find the second switch console to unlock it. Climb over the fence and go through the gate. Cross the glass skyview and jump inside the tower perimeter. You can now access the ctOS tower.
You can't jump over the fences of this tower since they're barbed or sharp. Make your way to the docks north of the tower location and you open your Profiler. Use the camera nearby to trace the signal and find the switch console. After unlocking it, the gate near the docks should be open now. Head inside the perimeter and trace the second signal leading to the next switch console. Go through the gate and you should be able to access the tower.