What prisms or targets should I use to achieve optimal range and best accuracy with PLT 400?

If you are tracking a prism during layout, it is ideal to use a 360° prism from Hilti. The two choices and recommended tracking distances are:

1. POA 25 cat-eye prism: ideal for tracking up to 50m (shorter distances). In perfect conditions you might achieve 120m.
2. POA 20 glass prism: ideal for tracking up to 300m (longer distances). In perfect conditions you might achieve 400m.

For more distance and prism Information, please see the remainder of this article. Note that if you are using the PLT 300, your prism connectivity range will likely cap around 100m for glass prisms, and 50 meters for reflective foils and cat-eye prisms, but environmental conditions could allow further or shorter ranges.

Which prisms and targets are best for up to 100m range?

At a 100m range, the PLT 400 should be able to measure to the following targets:

1. POA 25 - This prism will likely be the primary prism you use with the PLT 300 and PLT 400.
   • Note - while measuring to this prism is possible at 100m, the software will prompt you to switch to a glass prism like the POA 20 (see below) if you are trying to track the prism beyond 50m.
2. POA 102 - a reflective target that can be used as a control point for stationing or reference.
3. POA 26 - a reflective target that can be used as a control point for stationing or reference.
4. POA 101 - a reflective foil that can be used as a control point for stationing or reference. Note - while you likely can lock on to this prism up to 30m away, beyond 30m would require that this target be manually centered with the camera.

Note - the POA 25 can also be purchased as the POA 16 when it is connected to the POA 10 plate (HCW plate).

Which prisms and targets are best for up to 300m range?

If needed, you can achieve even greater range for stationing by using a glass prism target, like the POA 103 (5). This prism can be reached at a range up to 300m. While the tablet itself cannot maintain connection to the tool at this range when using WiFi, the tool can still measure in targets at this distance if you have the appropriate prism to lock on to.

If you are consistently working at longer distances, especially if you are tracking a prism, utilizing the Bluetooth range extender POA 68 (6) and the POA 20 round glass prism (7) should help you get up to 300m range distance between the tablet and tool, as well as achieving up to 300m range for layout. Note that the Bluetooth range extender is not available in all regions, and when in use, the video feed from the tool will not be available, as that requires a WiFi connection rather than Bluetooth.

Is there a recommended vertical angle range I should be in when using prisms and targets?

Yes - there is a "recommended incident angle" for target locking. Limit the maximum vertical angle to 25°. While it is possible to lock onto a target at a 45° vertical angle, maintaining the center point of your targets and prisms is much more consistent when limiting your maximum vertical angle to 25°.

Which Prisms are best to be used as Control Points during Stationing?

As mentioned above in this article, it is recommended that you establish a stationing procedure that uses mountable prisms for their respective ranges (POA 101, POA 102, POA 103, POA 26). Perhaps the most popular option is the POA 103 glass prism because it can be reached at the longest range and can be locked onto automatically when in line of sight of your head unit.

The POA 25 and POA 20 prisms are typically designed to be used while performing layout with a prism rod. While you can use these prisms when measuring control points, you risk any instability or inaccuracies from manually positioning the prism rod. Remember, you want stationing to be a consistent and accurate process every time. If you are using the prism rod during your stationing procedure, make extra effort to keep your prism rod plumb and free of vibration.

What additional specifications can I use to help me identify the best targets to use?

According to the specification sheet for the PLT 400, the following information may also help you. Note, that these specifications are maximum measurement distances that can be achieved in perfect conditions.

Measuring to reflective targets when not in prism tracking mode:

Note - reflective means that the laser is targeting reflective targets like prisms or foils.

Single prism 50mm diameter: 900m (2,953ft)

Single prism 25mm diameter: 400m (1,312ft)

Cat-eye reflector 85mm: 300m (984ft)

Foil reflector 60mm: 300m (984ft)

Shortest possible range: 1m (3.3ft)

Measuring to non-reflective targets when not in prism tracking mode:

Note - non-reflective simply means that the instrument is measuring a target that is different from a prism or reflective foil. Real-world surfaces like concrete, asphalt, and soil usually have reflectivity values somewhere between these two extremes.

Kodak White (90% reflective): 840m / 150m (2,758ft / 492ft)

Kodak Gray Card (18% reflective): 375 m / 150m (1,230ft / 492ft)

Shortest possible range:0.5m (1.6ft)

Remember, external factors can affect range as well - please see this article regarding the overall accuracy of the PLT 400.