Instruments
A list appears under instruments showing those instruments that have been selected when importing one or more survey data files. The type of Instrument can then be selected for each observation under the observations tab in the Instrument column.
Data on the instruments can be obtained from the relevant supplier. The weights are calculated from these values, which means that an observation with a good instrument will affect the result more than the observations with an inferior result. The values you enter are the instrument's factory tested apriori mean error (see Report).
In general you could say that it is the standard mean error in particular that is directly influenced by the instrument data, as it is a comparison with the capacity of the instrument (1.000 means that you have measured exactly at a level the instrument can handle). As a result of this, the standard and observation mean errors as well as the sigma levels vary depending on the instrument data we choose. It should also be noted that the instrument data affects how the various observations are weighted in relation to each other, i.e. how much they affect the results. NOTE: It is therefore of the utmost importance that we have specified the correct values for the instrument's data if we want reliable assessments of the quality of the net. Note that you may not specify a value to 0.0000 as this is an unreasonable value that would apply to a completely error free instrument, which makes the weights impossible to calculate.
Settings
Instr.type
Different makes of instrument handle the corrections for pressure and temperature in different ways, which is taken into consideration under this setting. See also Atm. corr in the observations chapter.
HA Accuracy
Horizontal angle accuracy. Entered in GON (adjustable to mgon or degrees)
VA Accuracy
Vertical angle accuracy. Entered in GON (adjustable to mgon or degrees)
Length accuracy (constant)
Specified in meters (adjustable to millimeters)
Length accuracy (PPM)
Entered in PPM
centring error in plane
A centring error can either be specified for each point or generally for from and to points where the instrument is used. The centring error will give all observations that have been made using the instrument and offset in the accuracies specified above. E.g. the length accuracy will be calculated as a bit worse depending on the effect the centring errors have. If a field is blank in the centring error columns X and Y under the Points tab, the centring error specified for the instrument will be used.
centring error in height
See above.
Note that you may not specify a value to 0.00000 as this is an unreasonable value that would apply to a completely error free instrument, which makes the weights impossible to calculate.