Surveying Calculations

This module provides various surveying calculation commonly used in geodetic and surveying applications.

EDM Corrections

geodepy.survey.va_conv(zenith_angle, slope_dist, height_inst=0, height_tgt=0)

Function to convert vertical angles (zenith distances) and slope distances into horizontal distances and changes in height. Instrument and Target heights can be entered to allow computation of zenith and slope distances between ground points.

Parameters:

• zenith_angle – Zenith Angle from Instrument to Target, expressed in decimal degrees

• slope_dist – Slope Distance from Instrument to Target in metres

• height_inst – Height of Instrument. Optional - Default Value of 0m

• height_tgt – Height of Target. Optional - Default Value of 0m

Returns:

• vert_angle_pt - Vertical Angle between Ground Points, expressed in decimal degrees

• slope_dist_pt - Slope Distance between Ground Points in metres

• hz_dist - Horizontal Distance

• delta_ht - Change in height between Ground Points in metres

geodepy.survey.first_vel_params(wavelength, frequency, n_REF=None, unit_length=None)

Calculates the constant First Velocity Correction Parameters C and D for a given set of standard instrument settings

Reference Rueger, J.M., 2012, Electronic Distance Measurement: An Introduction, 4rd edition, Springer, Berlin

Parameters:

• wavelength – Instrument Carrier Wavelength (Micrometers) - Mandatory

• frequency – Instrument modulation frequency (Hz) - Optional

• n_REF – manufacturers reference refractive index - Recommended

• unit_length – unit length of instrument - Optional

Returns:

First Velocity Correction Parameters C and D

geodepy.survey.part_h2o_vap_press(dry_temp, pressure, rel_humidity=None, wet_temp=None)

Reference Rueger, J.M., 2012, Electronic Distance Measurement: An Introduction, 4rd edition, Springer, Berlin

Parameters:

• dry_temp – Observed Dry Temperature (degrees Celsius)

• pressure – Observed Pressure (hectopascals or millibars)

• rel_humidity – Observed Relative Humidity (percentage) - Optional if wet_temp supplied

• wet_temp – Observed Wet Temperature (degrees Celsius) - Optional if rel_humidity supplied

Returns:

Partial water vapour pressure

geodepy.survey.first_vel_corrn(dist, first_vel_param, temp, pressure, rel_humidity=None, wet_temp=None, CO2_ppm=None, wavelength=None)

Carries out First Velocity Correction of Electronic Distance Measurement, given correction parameters and atmospheric observations

Parameters:

• dist – Uncorrected Observed Slope Distance

• first_vel_param – Tuple of First Velocity Parameters C and D (see function first_vel_params)

• temp – Observed Temperature (degrees Celsius)

• pressure – Observed Pressure (hectopascals or millibars)

• rel_humidity – Observed Relative Humidity (percentage)

Returns:

First Velocity Correction

geodepy.survey.mets_partial_differentials(group_ref_Index=1.00028, temp=15, pressure=1013.25, rel_humidity=60)

Calculates the sensitivity coefficients for temp, pressure and humidity in ppm

Parameters:

• group_ref_Index – manufacturers group refractive index of light

• temp – Observed Dry Temperature (degrees Celsius)

• pressure – Observed Pressure (hectopascals or millibars)

• rel_humidity – Observed Relative Humidity (percentage) - Optional if wet_temp supplied

Returns:

Sensitivity Coefficients K, L and M in ppm

geodepy.survey.refractivity_constants()

Returns:

Refractivity constants used in the refractivity calculations.

geodepy.survey.phase_refractivity(LAMDA, TC, P, PV, XC=420)

Calculates the phase refractivity of moist air using Ciddor’s equations

Parameters:

• LAMDA – wavelength (micrometre)

• TC – temperature (degrees Celcius)

• P – pressure (hPa)

• PV – partial water vapour pressure (Pa)

• XC – carbon dioxide content (ppm)

Returns:

NPROPP_1 - phase refractivity = (NPROPphase-1)10E8

geodepy.survey.group_refractivity(LAMDA, TC, P, PV, XC=420)

Calculates the group refractivity of moist air using Ciddor’s equations

Parameters:

• LAMDA – wavelength (micrometre)

• TC – temperature (degrees Celcius)

• P – pressure (hPa)

• PV – partial water vapour pressure (Pa)

• XC – carbon dioxide content (ppm)

Returns:

NPROPG_1 - group refractivity = (NPROPgroup-1)10E8

geodepy.survey.humidity2part_water_vapour_press(H, TC)

Calculates the partial water vapour pressure from relative humidity and temperature

Parameters:

• H – humidity (%)

• TC – temperature (degrees Celcius)

Returns:

PV - partial water vapour pressure (Pa)

Angle Calculations

geodepy.survey.joins(east1, north1, east2, north2)

Calculates the bearing and distance from point 1 to point 2

Parameters:

• east1 – Easting of Point 1

• north1 – Northing of Point 1

• east2 – Easting of Point 2

• north2 – Northing of Point 2

Returns:

Distance and Bearing from Point 1 to Point 2

geodepy.survey.radiations(east1, north1, brg1to2, dist, rotation=0, psf=1)

Calculates the coordinates of Point 2 given Point 1, bearing and distance

Parameters:

• east1 – Easting of Point 1

• north1 – Northing of Point 1

• brg1to2 – Bearing from Point 1 to Point 2 (decimal degrees)

• dist – Distance from Point 1 to Point 2 (metres)

• rotation – Rotation to be applied to bearing (decimal degrees) - Optional

• psf – Prism Scale Factor to be applied to distance - Optional

Returns:

Easting and Northing of Point 2