# PDU-4
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Introduced in **0.2.414**
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PDU-4 is a Russian binocular rangefinder with day optics with a 360° digital compass and a laser rangefinder. It provides distance measurements up to 9 km with 7x magnification.
PDU-4
The engraved reticle has a long line spacing of 10 mils and short line spacing of 5 mils. 1 mil corresponds to 1 m spacing at a distance of 1 km. In the image below you can see a 1 m cube being sighted at 100 m being exactly 10 mils.
PDU-4 Reticle Sighting a 1m Box at 100m
Due to unavailability of documentation, the functionality of the PDi in game is identical to that of [Vector-21](/rhs-status-quo-user-documentation/arma-reforger/rhs-status-quo/blufor/gadgets/vector-21.md). We suspect that in real life it is also close.
While looking through the binocular view you can perform the following actions:
| Keys | Description | Examples |
| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | -------------------------------- |
| Press and hold **`R`** key. Hold target for \~2 seconds in red targeting square. Release **`R`** key. | Measures distance in meters to target. |  |
| Press and hold **`V`** key. Hold target for \~2 seconds in red targeting square. Release **`V`** key. | Measures azimuth in degrees to target. |  |
| Press and hold **`R+V`** keys simultaneously. Hold target for \~2 seconds in red targeting square. Release **`R+V`** keys. | Measures distance in meters and azimuth in degrees to target. |  |
| Press and hold **`R`**, tap **`C`** to mark first point, move to second point and release **`R`** | Measure distance between 2 points. |  |
| Tap **`R`** once, press and hold **`R`**, tap **`C`** to mark first point, move to second point and release **`R`** | Measure horizontal and vertical distance between 2 points. The vertical distance is shown in the range indicator on the left. The horizontal distance in the azimuth indicator at the top. |  |
| Tap **`V`** once, press and hold **`V`** for \~2 seconds and release. | Measure azimuth and inclination to a point. Inclination, in degrees, is shown in the range indicator on the left. |  |
| Tap **`R`** once, press and hold **`R`** for \~2 seconds and release. | Measure horizontal and vertical distance to a point. The vertical distance is indicated in the range indicator on the left. |  |
| Press and hold **`V`**, tap **`C`** to mark first point, move to second and release **`V`**. | Measure distance and azimuth between two points. |  |
|
Tap V, press and hold V, tap C to mark first point (original target), move to second (arty impact) and release V.
The results are displayed together with letters (A. - add, d. - drop, L. - left, r. - right) which indicate the necessary correction terms together with the distance.
Example: If a shot is left and short, the correction is r.. and A.. with the appropriate value.
| Measure fall of shot between target and arty impact for correction. |  |
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