4.5. Observatory Operations
INTERMAGNET recommends:
Making weekly absolute observations, avoiding intervals of magnetic activity. If any baselines are changing rapidly increase the frequency of observations.
Making regular physical inspections of all observatory buildings to ensure that no magnetic materials which would cause jumps in baselines are present, inside or outside the absolute or variometer buildings.
Ensuring that absolute instruments and their supporting piers are free from contaminating magnetic materials.
Establishing an external-reference-site in an undisturbed area outside the absolute building; determining the absolute vector difference between that site and the main absolute pier. INTERMAGNET recommends annual comparison to check for magnetic contamination of either site. The external-reference-site may be a permanent pier, or a tripod site. If a tripod site is used, the location of the absolute instruments must be repeatable in latitude, longitude and height. The relocation precision depends on the distance to the azimuth mark and on the magnetic gradients at the site. Aim for a precision of 1mm in all three coordinates.
Ensuring that piers and azimuth marks are physically stable. Do not lean on piers during observations.
Comparing periodically the angles between multiple (non-collinear) azimuth marks to check that both the pier and marks are stable. If there is any change in any of the angles redetermine the azimuth to the primary azimuth mark independently (by means of astronomical observation, or differential-GPS for example). INTERMAGNET recommends annual checks.
Maintaining an up-to-date diary of absolute measurements, visits, repairs and other actions at the observatory.
Periodically reviewing procedures for absolute observations and adopting best practices; this may be facilitated by visiting other institutes and by attending the biannual IAGA observatory workshop.