Snowsense

The SM4 snow sensor

What is SM4?

SM4 is a lightweight, solar-powered snow sensor made for remote mountain sites. You carry it in on foot and set it up without heavy equipment. Each unit includes:

  • Temperature cable, 3 m or 5 m long, with 16 or 26 sensors spaced 20 cm apart.Custom lengths and spacing on request.

  • Laser distance sensor that measures snow depth directly, with an optional heater that keeps the lens free of ice.

  • Optional, low-cost wind sensor that measures wind speed and direction.

  • Data logger that collects readings from every sensor.

  • Communication unit that sends data every 10 minutes over LTE-M or NB-IoT. The data is shown on snowsense.is and available through our REST API.

  • Solar panel with battery backup.

SM4 uses very little power and runs all winter without an external power source. If the battery runs low, data can be sent less often to save power.

SM4 sensor unit with its temperature cableTop of an SM4 mast with the laser sensor, on a mountain ridge
Left: the SM4 unit with its temperature cable. Right: an SM4 mast on a mountain ridge.

SM4 was designed for avalanche monitoring from day one. It follows snow depth as it changes and shows how the snowpack is layered.

The temperature cable is mounted on a mast near potential avalanche starting zones and records a vertical temperature profile through the snow. Air temperature swings far more than snow temperature, so the profile clearly shows where the snow surface is.

Our algorithm uses this to calculate snow depth automatically. The same data also tells you:

  • Air temperature, a key input for avalanche forecasting.
  • The temperature profile of the snowpack, which reveals:

Snow that has melted and refrozen is usually stable and stays at a steady temperature close to 0 °C. As winter goes on, Icelandic snowpacks typically build a stable base like this, often with less stable layered snow on top. SM4 data shows that boundary clearly.

During a thaw, you can see when the snow turns wet and how deep the thaw reaches into new snow, which is key for judging wet-snow avalanche risk.

When the temperature changes by more than 1 °C per 10 cm, snow grains turn angular instead of rounding and bonding. These faceted grains bond poorly and can form the weak layers that slab avalanches release on. Our charts on snowsense.is show where and at what depth this may be happening.

SM4 has proven itself in Icelandic avalanche monitoring, and the network keeps growing.

Reading the chartsProducts