You can find the general key data locations in the hack menu. Some of them require you to find Key Data and can only be unlocked if you have them. Check your research App and press Y (Xbox One) / Triangle (PS4) on the Key Data you want to find and you will see the general location where you can find it.
Scan the world in your Quadcopter, RC Car or by yourself to get the exact location if you are near it. Many of the Key Data locations require you to have basic equipement like the RC Car or the Quadcopter. There are multiple solutions to some puzzles and only one or two require the "Environment RC" upgrade.
To get the Researcher Achievement / Trophy you need to collect all 24 Key Data upgrades. None of them are missable and they are saved instantly when you pick them up.
Here are the two timecode option. The first one shows it by area as shown in the video and the second one shows the timeline by Upgrades.
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COLLECT BY AREA (Order of the video)-------------------------------------------------------
MARIN1
00:03 Marksmanship / Steady Hands
2
00:32 Tinkering / Expert Tinkering
3
01:14 City Disruption / Massive System Crash
ALCATRAZ4
02:56 Remote CTRL / Speed Boost
OAKLAND5
04:00 Marksmanship / Fast Trigger Finger
6
04:30 Social Engineering / Gang War
7
05:13 City Disruption / System Crash Upgrade: Blackout
SAN FRANCISCO (Collected from top to bottom)8
06:03 City Disruption / Botnet Savings: City Hacking
9
08:07 Marksmanship / Target Weakness
10
08:43 Tinkering / Tweaked Blast
11
09:23 Vehicle Hacking / Massive Vehicle Hack
12
10:26 Marksmanship / Strong Grip
13
10:58 Vehicle Hacking / Engine Override
14
11:33 Remote CTRL / Remote Gadgets
15
12:10 Vehicle Hacking / Chopper Retreat Exploit
16
12:57 Marksmanship / Keen Eye
17
13:35 Remote CTRL / Expert RC Engineering
18
14:15 City Disruption / Security System Shutdown
19
14:56 Tinkering / Electro Shock Optimization
20
16:44 Remote CTRL / Enhanced Spring
21
17:47 Social Engineering / Botnet Savings: Personal Devices
22
18:27 Marksmanship / Stun Amp Up
23
22:00 Tinkering / Explosive Optimization
24
23:05 Vehicle Hacking / Botnet Savings: Vehicle Hacks
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COLLECT BY HACK UPGRADES-------------------------------------------------------
VEHICLE HACKING11
09:23 Massive Vehicle Hack
13
10:58 Engine Override
15
12:10 Chopper Retreat Exploit
24
23:05 Botnet Savings: Vehicle Hacks
SOCIAL ENGINEERING6
04:30 Gang War
21
17:47 Botnet Savings: Personal Devices
CITY DISRUPTION3
01:14 Massive System Crash
7
05:13 System Crash Upgrade: Blackout
8
06:03 Botnet Savings: City Hacking
18
14:15 Security System Shutdown
TINKERING2
00:32 Expert Tinkering
10
08:43 Tweaked Blast
19
14:56 Electro Shock Optimization
23
22:00 Explosive Optimization
MARKSMANSHIP1
00:03 Steady Hands
5
04:00 Fast Trigger Finger
9
08:07 Target Weakness
12
10:26 Strong Grip
16
12:57 Keen Eye
22
18:27 Stun Amp Up
REMOTE CTRL4
02:56 Speed Boost
14
11:33 Remote Gadgets
17
13:35 Expert RC Engineering
20
16:44 Enhanced Spring