Instrument Section

This section lists the instruments whose measurements are included in the USMN network solution. Instruments can have different weights applied. So, for example, if one instrument station was set up in an unstable location, i.e. near a HVAC blower, up high on a large tripod, on a separate concrete pad, etc. The influence of that particular station on the entire network could be reduced by reducing the instrument’s weight relative to the other stations.

Each instrument has a checkbox indicating whether that instrument is allowed to move during the calculation. A USMN bundle (or any bundle, or that matter) is a relative solution. That is, the solution can be reached relative to any instrument. As a result, all instruments may be checked (meaning all instruments will be perturbed to find the solution) or one may be unchecked (so that the solution is reached by perturbing all instruments EXCEPT the unchecked instrument). In both cases, the same end result is reached for the network itself, although the networks will end up in different places in space (and the uncertainties will be relative to different baselines). Regardless, al- lowing all instruments to move will typically take longer to solve, but the resulting point uncertainties will be more uniform and representative of a network in which no one instrument is more important than another. Although the network solution is the same, the calcu- lated uncertainties for the USMN Composite points will be different, because they are relative to different baselines. However, the relative uncertainties (differences between uncertainties) between each pair of points will remain the same.

More than one instrument may be fixed (unchecked) during a solution, although this is typically only done in rare cases and is generally not recommended, as the end result is a solution that is not an ideal spatial representation of an instrument network.

An individual instrument in this list may be double-clicked to access specific instrument properties. This instrument Proper- ties dialog provides access to the following settings:

In addition to individual instrument configurations there is also and option to choose between two Instrument Solution Reference Frame set- tings.