Backport GPS from v2.01 for CR1000X (fixes #13)

Default max allowed clock drift increased 0 to 1 ms.
After GPS is ready, lat/long is used to override user-defined settings.
Height compensation code not backported since such changes
are not backward compatible with user-defined settings.

CHANGELOG.md

@@ -19,6 +19,10 @@ Significant realignment means users will need to modify current deployments to c
 * **All sensor input locations were reverted to match EasyFlux-DL base code. This highly substantial change affects most sensors.**
   As a result of limited input locations, the 034B cup-and-vane anemometer and NR01 component radiometer are mutually exclusive by default (to use both, specify different input channels).
 * All hard-coded numbers for computations are changed from integer to float.
+* Support for GPS receiver updated to emulate CR6 or CR1000X program version:
+  * Menu options and public variable names are updated.
+  * Default maximum clock drift set to 1.0 millisecond.
+  * GPS latitude & longitude is updated as GPS fix improves and, once locked, is used instead of user-defined values.
 * Subroutine `FootprintCharacteristics_KormannMeixner`:
   * Incorporates thermal stratification as a function of stability from eqns (11) and (32) in *Kormann and Meixner (2001)*.
   * Modifies fourth footprint integration segment to increase integration interval by factor of 2.5 (4→10 x aerodynamic height)
@@ -45,6 +49,7 @@ Significant realignment means users will need to modify current deployments to c
 * Eliminate compiler warning about unused Topp equation function if not using Decagon 5TM sensors. Fixes [#4]
 * Fix *Time_Series* table to log alternate CO2 density derived from sonic temperature when using IRGASON (not just EC150). Fixes [#7]
 * Fix intermediate processing of energy balance SWC sensors and clean-up related code for profile sensors. Fixes [#3], [#8] and [#9]
+* Use non-zero default max clock drift. Fixes [#13]
 
 ### Removed
 
@@ -55,6 +60,7 @@ Significant realignment means users will need to modify current deployments to c
 [#7]: https://github.com/wsular/EasyFlux-DL-CR3000/issues/7
 [#8]: https://github.com/wsular/EasyFlux-DL-CR3000/issues/8
 [#9]: https://github.com/wsular/EasyFlux-DL-CR3000/issues/9
+[#13]: https://github.com/wsular/EasyFlux-DL-CR3000/issues/13
 
 
 ## [ProgSig 40826] 2018-11-29

doc/readme.md

@@ -124,7 +124,7 @@ Field names in data output tables contain a numeric index ranging from 1 to \{qt
 ### 3.1.13 GPS Receiver (new section)
 
 A GPS receiver is optional but will keep the datalogger clock synchronized to GPS time.
-If the datalogger clock drifts from the GPS time, then it will be resynchronized.
+If the datalogger clock drifts from the GPS time by more than `MAX_CLOCK_DRIFT` (default: 1 ms), then it will be resynchronized.
 The default wiring for the GPS receiver is shown in Table 3.13.
 
 > **NOTE**<br/>Units with serial numbers greater than 1A4189318 have a 3 V PPS output signal

src/EasyFlux-DL.cr3

@@ -116,6 +116,7 @@ Const SENSOR_DOOR        = FALSE                  'Unique: reed switch enclosure
 Const SENSOR_TS45        = FALSE                  'Unique: MorningStar TriStar TS-45 charge controller
 
 'adjust to reflect reality
+Const UTC_OFFSET = -8       'Unique: local time offset from UTC, in hours
 Const NMBR_SHFP = 4         'Unique: number of HFP01 or HFP01SC sensors to measure (Maximum is 4)
 Const NMBR_TCAV = 2         'Unique: number of TCAV (Maximum is 2)
 Const NMBR_CS6xx = 2        'Unique: number of CS616, CS650, CS655, TDR-315 or 5TM sensors (Maximum is 2)
@@ -576,9 +577,7 @@ Const o34B_WS_OFFSET = 0.28          'Unique: offset for wind speed
 #If (SENSOR_GPS16X) Then
 
 Const GPS16X_COM = Com4    'Serial port for GPS16X
-
-Const UTC_OFFSET = -8      'Unique: local time offset from UTC, in hours
-Const MAX_CLOCK_DRIFT = 0  'max clock drift permitted before setting clock, in msec
+Const MAX_CLOCK_DRIFT = 1.0  'max clock drift permitted before setting clock, in msec
 
 '*** Beginning of GPS16X wiring ***
 'C7      pulse-per-second (PPS) output (gray)
@@ -697,10 +696,10 @@ Units thick_abv_SHFP     = m
 Dim stn_conf_array_prev(NMBR_STN_VAR)            'Hold previous station parameters to check for new user-entered values
 
 'After user input, used to assign a sign to latitude and longitude
-Const Hemisphere_North =  1
-Const Hemisphere_South = -1
-Const Hemisphere_East  =  1
-Const Hemisphere_West  = -1
+Const NORTH =  1
+Const SOUTH = -1
+Const EAST  =  1
+Const WEST  = -1
 
 'Used to assign a value for surface_type
 Const CROP     = 1
@@ -2092,41 +2091,42 @@ EndTable
 #If (SENSOR_GPS16X) Then
 
 '*** Beginning of GPS receiver constants and variables ***
-Dim nmea_sentence(2) As String * 90
-
+Dim nmea_sentence(2) As String * 100        'Hold NMEA sentences: nmea_sentence(1) for GPRMC and nmea_sentence(2) for GPGGA.
 Public gps_data(15)
-Alias gps_data(1) = latitude_deg            'Degrees latitude (+ = East; - = West)
-Alias gps_data(2) = latitude_min            'Decimal minutes latitude
-Alias gps_data(3) = longitude_deg           'Degress longitude (+ = East; - = West)
-Alias gps_data(4) = longitude_min           'Decimal minutes longitude
+Alias gps_data(1) = latitude_GPS_deg        'Degrees latitude (+ = East; - = West)
+Alias gps_data(2) = latitude_GPS_min        'Decimal minutes latitude
+Alias gps_data(3) = longitude_GPS_deg       'Degress longitude (+ = East; - = West)
+Alias gps_data(4) = longitude_GPS_min       'Decimal minutes longitude
 Alias gps_data(5) = speed                   'Speed
 Alias gps_data(6) = course                  'Course over ground
 Alias gps_data(7) = magnetic_variation      'Magnetic variation from true north (+ = East; - = West)
 Alias gps_data(8) = fix_quality             'GPS fix quality: 0 = invalid, 1 = GPS, 2 = 'differential GPS, 6 = estimated
 Alias gps_data(9) = nmbr_satellites         'Number of satellites used for fix
-Alias gps_data(10) = altitude               'Antenna altitude
+Alias gps_data(10) = altitude_GPS           'Antenna altitude
 Alias gps_data(11) = pps                    'Elapsed ms since last pulse per second (PPS) from GPS
 Alias gps_data(12) = dt_since_gprmc         'Time since last GPRMC string, normally less than '1 second
 Alias gps_data(13) = gps_ready              'Counts from 0 to 10, 10 = ready
 Alias gps_data(14) = max_clock_change       'Maximum value the clock was changed
 Alias gps_data(15) = nmbr_clock_change      'Number of times the clock was changed
-Units latitude_deg = degreesN
-Units latitude_min = minutesN
-Units longitude_deg = degreesE
-Units longitude_min = minutesE
+Units latitude_GPS_deg     = degrees
+Units latitude_GPS_min     = minutes
+Units longitude_GPS_deg    = degrees
+Units longitude_GPS_min    = minutes
 Units speed = m/s
 Units course = degreesEofN
 Units magnetic_variation = degreesEofN
 Units fix_quality = unitless
 Units nmbr_satellites = unitless
-Units altitude = m
+Units altitude_GPS         = m
 Units pps = ms
 Units dt_since_gprmc = s
 Units gps_ready = unitless
 Units max_clock_change = ms
 Units nmbr_clock_change = occurrences
+
+Dim gps_ready_best As Long
 '*** End of GPS receiver constants and variables ***
-#EndIf
+#EndIf '(SENSOR_GPS16X)
 #If (SENSOR_DOOR) Then
 
 '*** Beginning of door switch constants and variables ***
@@ -2246,11 +2246,11 @@ DisplayMenu ("System Control", TRUE)
 
     MenuItem ("Sonic Azmth", sonic_azimuth)
     MenuItem ("Latitude",    latitude)
-    MenuItem ("Hemisph_Eq",  hemisphere_NS)
-  MenuPick (Hemisphere_North, Hemisphere_South)
+    MenuItem ("Hemisph_NS",  hemisphere_NS)
+      MenuPick (NORTH, SOUTH)
     MenuItem ("Longitude",   longitude)
-    MenuItem ("Hemisph_Me",  hemisphere_EW)
-  MenuPick (Hemisphere_East, Hemisphere_West)
+    MenuItem ("Hemisph_EW",  hemisphere_EW)
+      MenuPick (EAST, WEST)
 
     SubMenu ("Planar Fit Alpha")
       MenuItem ("<=60 or >=300",  alpha_PF_60_300)                               'Angle in sonic coordinate system
@@ -4778,6 +4778,11 @@ BeginProg
 
   '*************************** SCAN LOOP  **************************************************
   Scan (SCAN_INTERVAL, mSec, SCAN_BUFFER_SIZE, 0)
+    #If (SENSOR_GPS16X) Then
+    '*** GPS16X measurements
+    GPS (latitude_GPS_deg, GPS16X_COM, UTC_OFFSET*3600, MAX_CLOCK_DRIFT, nmea_sentence(1))
+    #EndIf
+
     'Datalogger panel temperature
     PanelTemp (panel_tmpr, 250)
 
@@ -6145,10 +6150,15 @@ BeginProg
     #EndIf
 
     #If (SENSOR_GPS16X) Then
-
-    '*** Beginning of GPS16X-HVS measurements ***
-    GPS (gps_data(1),GPS16X_COM,UTC_OFFSET*3600,MAX_CLOCK_DRIFT,nmea_sentence(1))
-    '*** End of GPS16X-HVS measurements ***
+    'Correct input values of latitude and longitude using GPS data 
+    If (gps_ready > gps_ready_best) Then 
+       latitude = latitude_GPS_deg + latitude_GPS_min/60
+       hemisphere_NS = SGN (latitude_GPS_deg)*1
+       longitude = longitude_GPS_deg + longitude_GPS_min/60
+       hemisphere_EW = SGN (longitude_GPS_deg)*1
+
+       gps_ready_best = gps_ready
+    EndIf
     #EndIf
 
     '*** Beginning of updating files of station variables and planar fit angles ***
@@ -6160,13 +6170,13 @@ BeginProg
       Select Case stn_var_check_count
         'Update geo-coordinates
       Case 2, 3, 4, 5
-        If (hemisphere_NS = Hemisphere_North) Then
+        If (hemisphere_NS = NORTH) Then
           latitude = ABS(latitude)
         Else
           latitude = - ABS(latitude)
         EndIf
 
-        If (hemisphere_EW = Hemisphere_East) Then
+        If (hemisphere_EW = EAST) Then
           longitude = ABS(longitude)
         Else
           longitude = -ABS(longitude)