Options sightshot points calculation

Options for station points table:

For station points table there is possibility that when adding a coordinates file only points with a certain code to be taken over. Identification code of station points is also used to form file name in which stations are saved. Code is added, in parenthesis, to file name so that coordinates file with saved stations will not be confounded with coordinates file with calculated sightshot points.

Options for measurements table:

When measured points are introduced manually there is possibility to increment point’s number with a value.

To import measurements from an instrument you can use codes to identify stations and vises to backsight points (for stations orientation). These codes are not used for instruments that have station or points measured forward or backward defined in data format. You can find examples about this matter at “C:\Program Files\TopoLT\Example\PolarPoints\”. Read files given as example to understand how these codes must be introduced when measurements are made.

Options for table with calculated sightshot points:

When calculation is made the station points existing in station points table can be added at the beginning of table with calculated sightshot points.

At this function you can also choose if you calculate elevations for sightshot points. In case not then column with Z elevations will be 0.000 for all points.

Corrections used at calculation:

There can be applied angular corrections to eliminate horizontal collimation and index error for measured angles (Hz, V). This possibility was introduced because, usually, sightshot points are measured in a single telescope position. If you know the values of horizontal collimation and index value for the instrument with what measurements were made you can introduce them to correct measured angles. In order to avoid applying these corrections twice check if the instrument does nor apply them when measurements are recorded.

There can be applied corrections to eliminate the influence of earth curvature and atmospheric refraction at the calculation of horizontal distances and of height differences.

Horizontal distances can be reduced to projection plan by using a scale factor or by introducing value in cm/Km or feet/miles.

When distances are measured stadimetrical, using classical theodolites, horizontal distances and height differences are corrected with sin(V).

Tolerances:

Tolerances are used in case of multiple determinations to indicate if a measured value exceeded media.

Orientation tolerance is used when a station’s orientation is determined from several points and N, E, Z tolerance is used when a point is measured several times.

Calculation formulas for corrections:

Index error:

V = V0 + Eidx;

Horizontal collimation:

Hz = Hz0 + Ecol / sin(Eidx);

Influence of earth curvature and atmospheric refraction (k = 0.13):

dH = Di * cos(V) + (Di * sin(V))² * 6.8E-8;

Do = Di * sin(V + 6.5E-7 * Di * sin(V)) – 1.57E-7 * dH * Di * sin(V);

For distances measured stadimetrical:

dH = dH * sin(V);

Do = Do * sin(V);

To reduce distances to projection plan:

Do = Do * m;

Where:

V - corrected value of zenithal angle;

V0 - measured value of zenithal angle;

Hz - corrected value of horizontal angle;

Hz0 - measured value of horizontal angle;

Eidx - index error;

Ecol - horizontal collimation;

Di - measured value of slope distance;

Do - calculated horizontal distance;

dH - calculated slope distance;

m - scale factor.