Prism Installation

Prism Mounting and Installation Guidelines and Best Practices

TotaLite detects movement using the reflections of retroreflectors. To hit the required accuracy and range, TotaLite works with standard surveying prisms (minimum 17mm diameter) at distances up to 70 meters. For the sake of the argument, we can refer to prisms as targets. Other retroreflectors, like foil prisms or reflective stickers, aren't supported.

Mount prisms rigidly to the structure you're monitoring, so any movement reflects real deformation rather than play in the mount — drill into concrete or another stable surface. Keep at least 2° of angular separation between targets as seen from the camera, since overlapping targets can't be distinguished. Prisms can be placed as close as 5 meters from the sensor, with LED power adjusted accordingly.

Avoid large distance differences between prisms in the same network. If one prism sits at 5m and another at 70m, the sensor needs full power to reach the 70m prism — which will overexpose the one at 5m and degrade its displacement data. Use the table below to match power to your prism distances:

Requirements for mounting the targets

• Use standard surveying prims (>17mm) made with reflectors; such as L-bar mini-prisms.
• Ensure rigid installation of the prisms such that any motion would reflect real displacement
• Maximum range 70m from TotaLite Sensor under direct sunlight exposure
• Use recommended retroflectors such as L-Bar prisms.
• Respect acceptable distances between farthest and closest target
• ⚠️ Mount the Prisms to guarantee >2° target separation in TotaLite Sensor field of view.

Minimum separations between targets

Get placement right, and the sensor does the rest.

Targets need to sit within the sensor's range and field of view, spaced far enough apart that they don't overlap. Because angular separation is fixed, targets further from the sensor need more physical space between them than targets close by.

Best practices for Target Mounting

• Ensure the centre of the target is facing directly the TotaLite Sensor
• Mount targets rigidly to ensure any motion reflects actual structural deformation
• Ensure stable connection to the monitored structure (e.g., drilled into concrete)
• Consider potential overlap between targets from the camera's perspective
• Plan target placement to avoid obstruction by site activities
• Clean targets regularly to maintain reflectivity
• Remove any reflectors that are not monitoring targets

Environmental considerations

• Weather conditions - Extreme weather such as torrential rain could obstruct reflections from the target
   
• Sunlight - Bright sunlight reduces the range for target detection and influences power settings (the brighter the sun, the more target exposure would be required, the higher the power should be set).
   
• Dirt and Debris -Dust, dirt and debris on a monitoring site, could potentially hinder the degree of reflectivity of the prisms.