Dashcam

A dashboard camera or simply dashcam, also known as car digital video recorder (car DVR), driving recorder, or event data recorder (EDR), is an onboard camera that continuously records the view through a vehicle's front windscreen and sometimes rear or other windows. Some dashcams include a camera to record the interior of the car in 360 degrees inside camera, usually in a ball form and can automatically send pictures and video using 4G. 
EDRs and some dashcams also record acceleration/deceleration g-force, speed, steering angle, GPS data, etc. 
A wide-angle 130, 170° or more front camera may be attached to the interior windscreen, to the rear-view mirror (clip on), or to the top of the dashboard, by suction cup or adhesive-tape mount. A rear camera is usually mounted in the rear window or in the registration plate, with a RCA video output to the display monitor/screen.
The resolution will determine the overall quality of the video. Full HD or 1080p (1920×1080) is standard for dash HD cams. Dash cameras may have 1080p, 1296p, 1440p, or higher definition for a front camera and 720p for a back camera and include f/1.8 aperture and night vision mode. 
Dashcams can provide video evidence in the event of a road accident. When parked, dashcams can capture video and picture evidence if vandalism is detected by 360° parking monitor and send it to the owner usually employing 4G.
Types.
By targeted field of view: 
Some cabin cams include a screen also known as a rear view mirror dash cam) that can be attached to the rear-view mirror employing usually rubble rings or straps or as a direct replacement of the rear view mirror itself. Others attach to the windshield, dash, or other suitable interior surfaces
Many dashcams include rechargeable batteries not needed when connected to car battery wire or capacitors.
Functions.
To ensure that recorded video files are not tampered with once they have been recorded, videos can be timestamped in a tamper-proof manner, a procedure termed trusted timestamping.
To ensure a reliable 24/7 parking surveillance when capacity is an issue, a motion detector may be used to record only when an approaching human/vehicle is detected, in order to save power and storage media.
Advanced driver assistance system ADAS and park location save can be included.
G-sensor.
Dashcams with a G-sensor ensure that recordings of a collision are not overwritten by new data usually by storing them in a separate folder and/or making them read-only. The G-sensor ensures that the dashcam makes separate recordings.
Radar detector.
The integrated radar detector responds to police radars and warns the driver about approaching them, as a rule, with a sound signal.
Screen.
Some dashcams include touch screens, which vary in size the wider ones are usually mounted on the rearview mirror.
SD, satellite and wireless.
Dashcams usually use class 10 or above MicroSDHC or MicroSDXC cards usually 16 GB or higher or internal memory to save videos.
The port to connect the GPS antenna can use a micro USB or 3.5 mm jack connection. The antenna is usually 1575 to 1568 MHz and 3.0 to 5.0 V.
GPS coordinate stamping capability is included in most dashcams (some need an external GPS antenna, but other dashcam systems have built-in GPS), and others include GPS (online and offline) navigation.
Some dashcams include Wi-Fi, Bluetooth, and 4G connectivity.
For Bluetooth and voice commands and recording, a built-in microphone is included.
4G triple-cam (also called triple-lens and three-way-cams) sets on rearview mirror are becoming more available (2 front cameras - one 170° to mainly record road, one 360° for sides and doors and a rear camera).
4G is used to send messages, calls, pictures, and videos in parking surveillance mode. Usually a second 360° camera is employed to record the car's sides front doors and windows and inside.
Also, 4G is used to send message when car battery is low.
Hardwire.
Dashcam units usually operate via the vehicle electrical system, converting the 13.8V to a 5V USB connector. Dashcams can be plugged in via the cigarette lighter socket, or may be hardwired directly into the electrical system, freeing up the power outlet for other uses.
In order to store files and properly format the media card when power is turned off, dashcams use either a Lithium Polymer (LiPo) battery or a capacitor. While both provide power for a very short period of time, they have very different operating capabilities and limitations. LiPo batteries have an estimated life of 2-3 years or roughly 300-500 cycles. Over time, the material inside the battery will start to degrade resulting in out-gassing. This can be observed in a swollen or puffy looking battery case. When a LiPo battery reaches this point, the battery is no longer able to hold a charge. The result is a camera that may randomly turn on or off, or register format errors if it can't shut down correctly when power is turned off since it can only function when using the power from the vehicle. Capacitors can also store a temporary charge and will last much longer. They are also more resistant to higher operating temperatures, but are more expensive and require additional hardware or software support. Generally the LiPo batteries are found in less expensive dashcams and capacitors are used in more expensive dashcams.
Culture.
Dashcams are widespread in Russia as a guard against police corruption and insurance fraud, where they provide additional evidence. They have been called "ubiquitous" and "an on-line obsession," and are so prevalent that dashcam footage was the most common footage of the February 2013 Chelyabinsk meteor, which was documented from at least a dozen angles. Thousands of videos showing automobile and aircraft crashes, close calls, and attempts at insurance fraud have been uploaded to social sharing websites such as YouTube, Facebook, Twitter, Yandex, and other websites.
In the United Kingdom, sales of dashcams rocketed in 2015, which was the fastest growing consumer electronic, with sales increasing by 395%.
In China, dashcams were well known by a dramatic event of a road rage.
Dashcams have also captured numerous aviation accidents, such as National Airlines Flight 102 in 2013, TransAsia Airways Flight 235 in 2015,the Shoreham Airshow crash in 2015, and a catastrophic engine failure of United Airlines Flight 328 in 2021.
Dashboard cameras have become the top feature wanted by future vehicle buyers and more car manufacturers are incorporating built-in camera systems.
Legality.
While dashcams are gaining in popularity as a way of protection against distortion of facts, they also attract negative attitudes for privacy concerns. This is also reflected in the laws of different countries in different and conflicting ways:
Police use.
Police departments use dashcams in police vehicles to gather evidence during traffic stops and car chases. Some dashcam systems can be automatically activated when a police car's emergency lights or siren are turned on. Freedom of information laws mean that the footage can be released under some circumstances, and this can be an important tool in reporting on police actions. TV shows like "World's Wildest Police Videos" have frequently featured car chase videos shot from dashcams.
Some police officers accused of police brutality tamper with their cameras to disable audio or video recording. A report in 2016 showed that in Chicago, 80% of the police dashcams did not work properly. Among the causes were that officers destroyed antennas, hid microphones, and removed batteries.