Transferring true north to a sensor pit

When deploying a seismometer in the field, it must be aligned with true north. If for any reason you need to orient your sensor to anything other than true north, contact SEIS-UK for assistance.

Once you have found true north as described in previous sections, you need to transfer a true north line to the location that your sensor is going to be installed, e.g. a sensor pit. This can be done in a number of ways:

1. Score a line oriented to true north at the bottom of the sensor pit. If concrete is being put in the pit as a base for a sensor, the north/south line should be scribed in the concrete before it sets.
2. Place something straight oriented towards true north across the top of a sensor pit, e.g. a ruler, stake or fishing line.
3. Place a stake in the ground due north from your sensor installation location. When lying down to put the sensor in the pit, you should be able to sight the stake and align north on the sensor with the direction of the stake.

It should be noted that the components of the seismometer may affect a compass, and therefore any guide lines drawn in a pit or set out above the pit should be established with the seismometer away from the compass.