Data Recorder Configuration

Geoida requires data files down-loaded from the SDR2/20/22 or SDR33 using the Comms Output data-transfer mode (i.e., not Printer Output mode), and caters for most variations of data collected using the Traverse, Topography, Coordinates, Resection and Collimation programs in either the 4-digit point number (SDR2x) or 14-character alpha-numeric point ID (SDR33) formats. However it is essential that the SDR is correctly initialised for the particular theodolite/EDM combination or total station - parameters incorrectly set may cause unresolvable errors.

SDR parameter settings supported by Geoida are :

* The N setting is recommended for these corrections, as Geoida is able to apply the spheroidal distance and curvature-refraction corrections. However, if these parameters in the SDR were already set to Y, the Apply Curv/Refrac and the Reduce Dists to Spheroid check boxes must be UNcrossed to avoid applying the corrections a second time.


Supported record types

The following record types are supported.

00 - Header record
01 - Instrument details
02 - Station details
03 - Target details
04 - Collimation values
05 - Environment (atmospheric) details
06 - Scale factor
07 - Back-bearing details
08 - Coordinates
09 - Observation
10 - Job identifier
11 - Reduced measurements
12 - Set of observations
13 - Note
24 - GPS coordinates

The data may be in two different formats, namely the SDR2x 4-digit point number format or the SDR33 14-character alpha-numeric point ID format. The SDR33 is able to record in either format which is defined at the time of the initial job definition in the instrument. The two formats are similar except that the SDR33 format has larger record fields which are particularly suited to recording longer grid coordinate values without truncation.

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Vertical and horizontal tolerances

Vertical and horizontal tolerances should be entered, so that bad sets of observed traverse angles may be rejected by the data recorder. However, if the survey accuracy is low (eg sighting to hand-held targets), the tolerance values should be reset to appropriately larger values.

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Atmospheric corrections

The atmospheric-corrections parameter is not supported. Therefore, either

  1. the corrections must be dialed-in on the EDM or total station - set the SDR Atmosp. Correction parameter to N and manually set the dial-in corrections on the instrument


  2. the SDR must be set to correct for atmospherics - Set the SDR Atmosp. Correction parameter to Y and set the EDM dial-in corrections to zero. With this setting, the SDR will prompt for pressure and temperature but it is essential that the SDR INSTRUMENT parameter be set to the correct total station or EDM/theodolite combination. With this setting, it is important that the Topography Program mode (see heading below) be set to MC obsvn, Reduced, or Coords (rather than Raw), or if using the Coordinates Program (see heading Coordinates Program under Preparing SDR Data for Processing) that coordinate values always be stored - the reason for this is that Geoida does not make atmospheric corrections to the raw observations collected by either of these programs.

Thus, it is strongly recommended that point (i) be the practice adopted.

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Collimation program

It is recommended that the Collimation program be used at the start of each job with the SDR.

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Traverse and Set Collection programs

When computing in Traverse/Network mode, Geoida reads only meaned and corrected (MC) traverse or set-collection observations from the data file following a 12TV or 12SC code - raw observations are by-passed. Observations in MC format may be a configurable download option (SDR33).

It is recommended that the Direction method of angle collection be used for traverse or set observations, as the Repetition method can make editing of data difficult, especially if the horizontal and vertical tolerances were not set and bad angles have been observed. When a job is to consist of both traversing and detail pick-up, the SDR Traverse, Set Collection and Topography programs may be used in any order at a setup, although the traverse or set observations should be made first as a matter of practice, to avoid the superfluous re-calculation of raw traverse observations during the reduction in Radiations mode in Geoida.

Geoida recognises the 'Bad Marker' in any type 12 'Set' record (SDR33 only) and will not include any sets marked as bad in the extracted observations.

Note - MC records collected by the Topography program as means of Face1/Face2 pairs are not processed as radiations but as traverse or network observations. These observations are read and computed when either of the All data or Traverse/Network modes is selected but not in Radiations only mode.

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Topography program

Any one of the Coords, Reduced, MC obsvn or Raw obsvn modes may be used for pick-up observations - however, it is suggested that, for single-face observations, the RAW obsvn mode be used whenever possible, so that in the event of errors having been made, the data may be easily edited.

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Unsupported options

Although the SDR Scale Factor record is read by Geoida and may be recorded in the reduction log file, it is otherwise not used in any computations. A value for Scale Factor might be specified during the field survey as an approximate value for the grid point scale factor to permit the data recorder to compute 'pseudo' grid projection coordinates for checking closures etc in the field, but since Geoida computes coordinates using rigorous algorithms, the scale factor is otherwise of no value as Geoida computes its own, relative to the current location. Care should be taken by the SDR operator to make certain that data is collected in raw (OBS) or corrected (MC) form as these can be further reduced and processed by Geoida to give accurate results. However, if the field data is collected as position (POS) or reduced (RED) records only, these cannot be further processed by Geoida as numerous corrections and reductions including scale factor will have irreversibly been applied by the SDR, and any point coordinate records read will then simply be entered directly into the Geoida database as-is.

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The scale factor used internally by the SDR is also applied in reverse to internally-stored point coordinates to derive set-out measurements. If spheroidal points have been computed by Geoida and then re-loaded to the SDR for setout, the SDR Scale Factor to be applied is NOT just the projection scale factor but must also take into account the terrain height.

For comprehensive listings of SDR codes, options and settings, refer to the appropriate SDR documentation (Eg, References, SDR2 Electronic Field Book - Application Guide and Interfacing with the SOKKIA SDR33 Electronic Field Book).

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