To make changes to the corrections prior to performing reductions use the Corrections option from the Settings menu, or press the Parameters button in the Reduction dialog box.
Select the corrections you wish to apply by checking the appropriate tick box. For more information regarding the corrections please click an area of interest on the picture above.
Universal Transverse Mercator (UTM)
If your calculations are based on an Ordinance Survey co-ordinate system you will require this correction to correctly modify the observed slope distances. The following equation is used to calculate the scale factor:
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Where |
Fp |
Scale factor to be applied to observed slope distances. |
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Sm |
Indicated value for Scale at Meridian. |
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Es |
Eastings of the set-up station in National Grid coordinates. |
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Eo |
Easting of the National Grid Origin. |
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Re |
Earth's Radius. |
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Cl |
Local Correction is location dependent. |
The OS Projection is based on a central meridian 2° WEST of Greenwich.
Curvature and Refraction Correction
The following equation is used to correct for the effect of curvature and refraction errors in a survey:
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Where |
VA |
Vertical Angle. |
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Sd |
Slope distance observed to target. |
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Cr |
Curvature & Refraction Coefficient. |
Mean Sea Level
This Mean sea level correction is applied as follows:
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Where |
HD |
Horizontal radial distance from instrument to target used for calculating coords. |
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PD |
Distance to target observed as plan length. |
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Ih |
Height of instrument relative to OS Datum. |
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δTH |
Height difference from EDM to target prism. |
Scale Factor
The Scale factor to be applied to the co-ordinate calculation.
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