Merge pull request #142 from KentWheeler/master

first velocity correction according to Rueger

Author: BatchelorJ

geodepy/survey.py

@@ -10,26 +10,66 @@
 from geodepy.convert import rect2polar, polar2rect
 
 
-def first_vel_params(wavelength, temp=12, pressure=1013.25, rel_humidity=60):
+def 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
-    :param wavelength: Instrument Carrier Wavelength (micrometres)
-    :param temp: Standard Temperature (degrees Celsius)
-    :param pressure: Standard Pressure (hectopascals or millibars)
-    :param rel_humidity: Standard Relative Humidity (percentage)
+    :param wavelength: Instrument Carrier Wavelength (Nanometers) - Mandatory
+    :param frequency: Instrument modulation frequency (Hz) - Mandatory
+    :param n_REF: manufacturers reference refractive index - Recommended
+    :param unit_length: unit length of instrument - Optional
     :return: First Velocity Correction Parameters C and D
+    Reference Rueger, J.M., 2012, Electronic Distance Measurement – An Introduction, 4rd edition, Springer, Berlin
     """
-    group_refractivity = 287.6155 + (4.8866 / wavelength ** 2) + (0.068 / wavelength ** 4)
-    param_d = (273.15 / 1013.25) * group_refractivity
-    saturation_pressure = ((1.0007 + ((3.46 * pressure) * (10 ** -6)))
-                           * 6.1121 * exp((17.502 * temp) / (240.94 + temp)))
-    param_c = ((((group_refractivity * pressure) / (273.15 + temp)) * (273.15 / 1013.25))
-               - (11.27 * ((saturation_pressure * (rel_humidity / 100)) / (273.15 + temp))))
+    
+    if not n_REF and not unit_length:
+        raise ValueError('Error - n_REF and unit_length cannot both be None')
+        
+    if not n_REF:
+        # Rueger eq 6.3
+        n_REF = 299792458 / (2 * unit_length * frequency)
+    
+    # Rueger eq 6.12
+    param_c = (n_REF-1)*10**6
+    
+    # Rueger eq 5.12
+    # https://office.iag-aig.org/doc/5d7b8fda0c032.pdf Resolution 3
+    nG_1_10_6 = 287.6155 + (4.8866 / wavelength ** 2) + (0.068 / wavelength ** 4)
+    # Rueger eq 6.13
+    param_d = (273.15 / 1013.25) * nG_1_10_6
+    
     return param_c, param_d
 
 
-def first_vel_corrn(dist, first_vel_param, temp, pressure, rel_humidity):
+def part_h2o_vap_press(dry_temp, pressure, rel_humidity=None, wet_temp=None):
+    """
+    :param dry_temp: Observed Dry Temperature (degrees Celsius)
+    :param pressure: Observed Pressure (hectopascals or millibars)
+    :param rel_humidity: Observed Relative Humidity (percentage) - Optional if wet_temp supplied
+    :param wet_temp: Observed Wet Temperature (degrees Celsius) - Optional if rel_humidity supplied
+    Reference Rueger, J.M., 2012, Electronic Distance Measurement – An Introduction, 4rd edition, Springer, Berlin
+    """
+    
+    if not rel_humidity and not wet_temp:
+        raise ValueError('Error - rel_humidity and wet_temp cannot both be None')
+                         
+    if rel_humidity:
+        wet_temp = dry_temp
+    # Rueger eq 5.27
+    E_w = ((1.0007 + ((3.46 * pressure) * (10 ** -6)))
+         * 6.1121 * exp((17.502 * wet_temp) / (240.94 + wet_temp)))
+    
+    if rel_humidity:
+        # Rueger eq 5.29
+        e = (E_w*rel_humidity)/100
+    else:
+        e = E_w - 0.000662 * pressure * (dry_temp - wet_temp)
+    
+    return e
+    
+
+def first_vel_corrn(dist, first_vel_param, temp, pressure,
+                    rel_humidity=None, wet_temp=None):
     """
     Carries out First Velocity Correction of Electronic Distance Measurement,
     given correction parameters and atmospheric observations
@@ -42,14 +82,44 @@ def first_vel_corrn(dist, first_vel_param, temp, pressure, rel_humidity):
     """
     param_c = first_vel_param[0]
     param_d = first_vel_param[1]
-    part_h2o_press = exp((17.269 * temp) / (237.3 + temp))
-    first_vel_corrn_ppm = param_c - (
-                (param_d * pressure) / (273.15 + temp) + ((11.27 * part_h2o_press) * (0.061078 * rel_humidity)) / (
-                    273.15 + temp))
+    e = part_h2o_vap_press(temp, pressure, rel_humidity, wet_temp)
+    
+    # Rueger eq 6.11
+    t_273_15 = temp+273.15
+    first_vel_corrn_ppm = (param_c-((param_d*pressure)/t_273_15)+((11.27*e)/t_273_15))
     first_vel_corrn_metres = dist * first_vel_corrn_ppm * (10 ** -6)
+    
     return first_vel_corrn_metres
 
 
+def mets_partial_differentials(group_ref_Index=1.00028, 
+                               temp=15, 
+                               pressure=1013.25,
+                               rel_humidity=60):
+    """ Returns the sensitivity coefficients for temp, pressure and humidity in ppm
+    :param group_ref_Index: manufacturers group refractive index of light
+    :param temp: Observed Dry Temperature (degrees Celsius)
+    :param pressure: Observed Pressure (hectopascals or millibars)
+    :param rel_humidity: Observed Relative Humidity (percentage) - Optional if wet_temp supplied
+    """
+    ng_1 = group_ref_Index - 1
+    t_273_15 = temp + 273.15
+    e = part_h2o_vap_press(temp, pressure, rel_humidity)
+    
+    param_k = (((((ng_1 * 273.15 * pressure)
+                  /1013.25)
+                 -(11.27 * e * 10**-6))
+                /t_273_15**2)
+               *(10**6))
+    param_l = (0.26957809 * (ng_1 / t_273_15)
+               *(10**6))
+    param_m = (((11.27 * 10**-6)
+               /t_273_15)
+               *(10**6))
+    
+    return param_k, param_l, param_m
+
+
 def precise_inst_ht(vert_list, spacing, offset):
     """
     Uses a set of Vertical Angle Observations taken to a

geodepy/tests/test_survey.py

@@ -6,27 +6,25 @@
 
 class TestSurveyConvert(unittest.TestCase):
     def test_first_vel_params(self):
-        temperature = 12
-        pressure = 1013.25
-        relative_humidity = 60
         edm_wavelength = 0.850
-        param_c = 281.781
+        frequency = 49951334.24
+        n_REF = 1.000281783
+        param_c = 281.783
         param_d = 79.393
-        params_new = first_vel_params(edm_wavelength, temperature,
-                                      pressure, relative_humidity)
+        params_new = first_vel_params(edm_wavelength, frequency, n_REF)
         self.assertEqual(round(params_new[0], 3), param_c)
         self.assertEqual(round(params_new[1], 3), param_d)
 
     def test_first_vel_corrn(self):
-        params = first_vel_params(0.85)
+        params = first_vel_params(0.85,49951.33424,1.000281783)
         raw_obs_distance = 1117.8517
         obs_temperature = 6.8
         obs_pressure = 960.8
         obs_relative_humidity = 58.6
         correction = first_vel_corrn(raw_obs_distance, params, obs_temperature,
                                      obs_pressure, obs_relative_humidity)
         corrected_obs_distance = raw_obs_distance + correction
-        self.assertEqual(round(corrected_obs_distance, 4), 1117.8618)
+        self.assertEqual(round(corrected_obs_distance, 4), 1117.8624)
 
     def test_va_conv(self):
         test1 = va_conv(92.24305555555556, 2116.254)