Preparing SDR Data for Processing

Corrections to MC observations

The SDR does not provide a facility for the in-field editing of measurement data. When observations are stored by the SDR in MC form, various corrections are made to the observed measurements including an adjustment for difference between the height of instrument and the height of prism/target, so that the values stored are the true slope distance and vertical angle between the actual points on the ground. If an incorrect prism height was input, it may be quite tedious to recompute and correct the observation during office-editing, because of the various corrections applied by the SDR. It is for this reason that RAW mode is suggested as perhaps the best for the Topography program (for single-face observations), as data in this form will permit straight-forward editing without complications, and Geoida will apply the various corrections as necessary. However, if errors due to incorrect prism heights result when data in MC form (either Topography, Traverse or Set Collection programs) is processed, corrections may be made by applying one of the following procedures :

  1. Adjust the heights of the computed points by the amount of the prism height error
  2. Compute original raw observation values from MC observations in data, and then re-compute the MC slope distance and vertical angle values based on the correct prism heights.

Traverse sets

Where multiple sets of angles have been observed at any particular instrument station and collected using the SDR Traverse or Set Collection programs, the last set recorded in the data is a mean of all previous sets. If any of the observed sets is in error, the meaned set will incorporate that error and will also be in error - therefore care will be required to correct for the error during editing. When reading SDR data using the Sokkia SDR2x/33 option, if the Mean control obsv'ns; read final MC sets only check-box is crossed, only the last of the sets at a setup will be read.

However, if it is suspected that a set may be in error (SDR2x), UNcrossing this check-box will cause all of the sets to be read and no observation meaning will be applied - the Extract file created may then be edited to correct the error and the reduction of the data may be continued by processing the Extract file through the Process Extracted Observations option where the meaning of observations may then be applied if required. But since Geoida recognises the 'Bad Marker' in any type 12 'Set' record in data collected with the SDR33, it will not include any sets marked as bad in the extracted observations.

Collimation observations

Radiated observations may be collected without exiting from the Collimation program - these are processed as normal radiation observations and the collimation values are incorporated into subsequent single-face observations.

Coordinates program

After reading an initial CO derivation code, Geoida provides the choice of reading coordinate details or of computing new values from the raw data (See Processing SDR), since the data usually consists of two lines of data for each observation - the first is the 09 observation record, and the second is the 08 record of computed coordinates for the point.

Resection program

After the first reading of a 02RS code which has blank coordinate values (the Resection program inserts such a line into the data when commenced, since it does not have any coordinates for the instrument station until computed), Geoida (in Radiations mode) does not compute coordinates for points subsequently observed until it reads a 02RS line with valid coordinate values and an accompanying 07 record or the 02 record for a new setup. When resections have been observed, the data should be first processed in Traverse/network mode and adjusted with the LS Network option so that coordinates for the resected point/s may be computed prior to reducing again in Radiations mode. Geoida computes resected points ONLY when set for LS Network adjustment in any of the traverse/network options. If no provisional coordinate values are otherwise available for the resected points, the Digitise Provisional Points option may be used to create the points in their approximate positions prior to the adjustment.

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