The Excel Resection by Angles Computation is a surveying calculation method used to determine the coordinates of an unknown point (station) by measuring angles and distances from three or more known points (reference objects or ROs) with known coordinates.
The input data required for this computation include the measured azimuth, the known coordinates of the reference objects (ROs), and the angles observed between the ROs and the unknown point (station).
The computation involves several steps, including converting the measured azimuth to a computed bearing, calculating the interior angles between the ROs and the unknown point, and applying trigonometric functions to determine the unknown point's coordinates.
The computation is performed using an Excel spreadsheet, which simplifies the calculations and allows for easy manipulation of the input data and results.
It is important to note that the known RO coordinates must be entered or observed in a clockwise direction to ensure the correct computation of the interior angles.
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What's never pointed out when discussing three-point resection is, fromĀ https://en.wikipedia.org/wiki/Position_resection_and_intersection,
When planning to perform a resection, the surveyor must first plot the locations of the known points along with the approximate unknown point of observation. If all points, including the unknown point, lie close to a circle that can be placed on all four points, then there is no solution or the high risk of an erroneous solution. This is known as observing on the "danger circle". The poor solution stems from the property of a chord subtending equal angles to any other point on the circle.
This is my Excel sheet from 2009 and can be found here (along with others):
https://www.engineeringsurveyor.com/utilities/index.htm#Excel