Feature: add support for NMEA 0183 MDA sentence type (#147)

* Adds support for NMEA 0183 MDA sentence type, containing meteorological composite. This message type is used by Thies Clima, and probably other major meteorological instrument makers.
SignalK · Apr 22, 2019 · b71b7fe · b71b7fe
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diff --git a/README.md b/README.md
@@ -22,6 +22,7 @@
 - [HDM - Heading - Magnetic](http://www.catb.org/gpsd/NMEA.html#_hdm_heading_magnetic)
 - [HDT - Heading - True](http://www.catb.org/gpsd/NMEA.html#_hdt_heading_true)
 - KEP - NKE Performance data
+- [MDA - Meteorological Composite](http://catb.org/gpsd/NMEA.html#_mda_meteorilogical_composite)
 - [MTW - Mean Temperature of Water](http://catb.org/gpsd/NMEA.html#_mtw_mean_temperature_of_water)
 - [MWV - Wind Speed and Angle](http://www.catb.org/gpsd/NMEA.html#_mwv_wind_speed_and_angle)
 - [RMB - Recommended Minimum Navigation Information](http://www.catb.org/gpsd/NMEA.html#_rmb_recommended_minimum_navigation_information)

diff --git a/hooks/MDA.js b/hooks/MDA.js
@@ -0,0 +1,126 @@
+/**
+ * Copyright 2016 Signal K <info@signalk.org> and contributors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+'use strict'
+
+ const utils = require('@signalk/nmea0183-utilities')
+
+ /*
+  * MDA - Meteorological Composite
+  *
+  *        1     2     3     4     5   6   7     8     9     10    11    12
+  *        |     |     |     |     |   |   |     |     |     |     |     |
+  * $--MDA,x.x,I,x.x,B,x.x,C,x.x,C,x.x,x.x,x.x,C,x.x,T,x.x,M,x.x,N,x.x,M*hh<CR><LF>
+  * Field Number:
+  *   1.    Barometric pressure, inches of mercury
+  *   2.    Barometric pressure, bars
+  *   3.    Air temperature, deg Celsius
+  *   4.    Water temperature, deg Celsius
+  *   5.    Relative humidity, percent
+  *   6.    Absolute humidity, percent <-- absolute is usually density, but NMEA probably using less common mass water per mass atmosphere formulation
+  *   7.    Dew point, deg Celsius
+  *   8.    Wind direction, degress True
+  *   9.    Wind direction, degress Magnetic
+  *  10.    Wind speed, knots
+  *  11.    Wind speed, m/s
+  *  12.    Checksum
+  */
+
+module.exports = function (input) {
+  const { id, sentence, parts, tags } = input
+
+  const values = []
+
+  // make SI units override any non-SI units
+  if( parts[0] !== '' ) {
+    values.push({
+      path: 'environment.outside.pressure',
+      value: 33.863886666667 * utils.float(parts[0]) // converting inHg -> hPa (SI units)
+    });
+  }
+  if( parts[2] !== '' ) {
+    values.push({
+      path: 'environment.outside.pressure',
+      value: utils.float(parts[2])*1000.0  // converting from bars to hPa (SI units)
+    });
+  }
+  if( parts[4] !== '' ) {
+    values.push({
+      path: 'environment.outside.temperature',
+      value: utils.transform(utils.float(parts[4]), 'c', 'k') // transform units Celsius to Kelvin (stick to SI units)
+    });
+  }
+  if( parts[6] !== '' ) {
+    values.push({
+      path: 'environment.water.temperature',
+      value: utils.transform(utils.float(parts[6]), 'c', 'k') // transform units Celsius to Kelvin (stick to SI units)
+    });
+  }
+  if( parts[8] !== '' ) {
+    values.push({
+      path: 'environment.outside.humidity',
+      value: utils.float(parts[8])/100.0 // converting from precentage to fraction
+    });
+  }
+  if( parts[9] !== '' ) {
+    values.push({
+      path: 'environment.outside.humidityAbsolute',
+      value: utils.float(parts[9])/100.0 // NMEA docs suggest this is a fraction/percentage, so probably they mean mass water per mass atmosphere formulation
+    });
+  }
+  if( parts[10] !== '' ) {
+    values.push({
+      path: 'environment.outside.dewPointTemperature',
+      value: utils.transform(utils.float(parts[10]), 'c', 'k')
+    });
+  }
+  if( parts[12] !== '' ) {
+    values.push({
+      path: 'environment.wind.directionTrue',
+      value: utils.transform(utils.float(parts[12]), 'deg', 'rad')
+    });
+  }
+  if( parts[14] !== '' ) {
+    values.push({
+      path: 'environment.wind.directionMagnetic',
+      value: utils.transform(utils.float(parts[14]), 'deg', 'rad')
+    });
+  }
+  if( parts[16] !== '' ) {
+    values.push({
+      path: 'environment.wind.speedOverGround',
+      value: utils.transform(utils.float(parts[16]), 'knots', 'ms')
+    });
+  }
+  if( parts[18] !== '' ) {
+    values.push({
+      path: 'environment.wind.speedOverGround',
+      value: utils.float(parts[18])
+    });
+  }
+
+  const delta = {
+    updates: [
+      {
+        source: tags.source,
+        timestamp: tags.timestamp,
+        values: values
+      }
+    ],
+  }
+
+  return delta
+}
diff --git a/hooks/index.js b/hooks/index.js
@@ -13,6 +13,7 @@ module.exports = {
   'HDT': require('./HDT.js'),
   'PBVE': require('./proprietary/PBVE.js'),
   'PNKEP': require('./proprietary/PNKEP.js'),
+  'MDA': require('./MDA.js'),
   'MTW': require('./MTW.js'),
   'MWV': require('./MWV.js'),
   'RMB': require('./RMB.js'),

diff --git a/test/MDA.js b/test/MDA.js
@@ -0,0 +1,101 @@
+/**
+ * Copyright 2016 Signal K and contributors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+ /*
+  * MDA - Meteorological Composite
+  *
+  *        1     2     3     4     5   6   7     8     9     10    11    12
+  *        |     |     |     |     |   |   |     |     |     |     |     |
+  * $--MDA,x.x,I,x.x,B,x.x,C,x.x,C,x.x,x.x,x.x,C,x.x,T,x.x,M,x.x,N,x.x,M*hh<CR><LF>
+  * Field Number:
+  *   1.    Barometric pressure, inches of mercury
+  *   2.    Barometric pressure, bars
+  *   3.    Air temperature, deg Celsius
+  *   4.    Water temperature, deg Celsius
+  *   5.    Relative humidity, percent
+  *   6.    Absolute humidity, percent <-- absolute shoud not be a fraction (something wrong with NMEA definition?! usually this is g/m3, in SI units)
+  *   7.    Dew point, deg Celsius
+  *   8.    Wind direction, degress True
+  *   9.    Wind direction, degress Magnetic
+  *  10.    Wind speed, knots
+  *  11.    Wind speed, m/s
+  *  12.    Checksum
+  */
+
+'use strict'
+
+const Parser = require('../lib')
+const chai = require('chai')
+
+chai.Should()
+chai.use(require('chai-things'))
+
+describe('MDA', () => {
+  it('check parsing with barometric pressure and wind speed in knots', () => {
+    const delta = new Parser().parse("$WIMDA,,I,+0.985,B,+03.1,C,+5.6,C,40.0,3.0,+3.4,C,90.0,T,85.0,M,10.0,N,,M*1A")
+
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.outside.pressure')
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.outside.temperature')
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.water.temperature')
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.outside.humidity')
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.outside.humidityAbsolute')
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.outside.dewPointTemperature')
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.wind.directionTrue')
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.wind.directionMagnetic')
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.wind.speedOverGround')
+
+    delta.updates[0].values.find(x => x.path === 'environment.outside.pressure').should.contain.property('value', 985)
+    delta.updates[0].values.find(x => x.path === 'environment.outside.temperature').should.contain.property('value', 276.25)
+    delta.updates[0].values.find(x => x.path === 'environment.water.temperature').should.contain.property('value', 278.75)
+    delta.updates[0].values.find(x => x.path === 'environment.outside.humidity').should.contain.property('value', 0.4)
+    delta.updates[0].values.find(x => x.path === 'environment.outside.humidityAbsolute').should.contain.property('value', 0.03)
+    delta.updates[0].values.find(x => x.path === 'environment.outside.dewPointTemperature').value.should.be.closeTo(276.55, 0.01)
+    delta.updates[0].values.find(x => x.path === 'environment.wind.directionTrue').value.should.be.closeTo(1.5707, 0.0001)
+    delta.updates[0].values.find(x => x.path === 'environment.wind.directionMagnetic').value.should.be.closeTo(1.4835, 0.0001)
+    delta.updates[0].values.find(x => x.path === 'environment.wind.speedOverGround').value.should.be.closeTo(5.14444, 0.0001)
+  })
+
+  it('check parsing with inHg pressure and wind speed in m/s', () => {
+    const delta = new Parser().parse("$WIMDA,29.92,I,,B,+03.1,C,+5.6,C,40.0,3.0,+3.4,C,90.0,T,85.0,M,,N,5.0,M*01")
+
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.outside.pressure')
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.outside.temperature')
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.water.temperature')
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.outside.humidity')
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.outside.humidityAbsolute')
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.outside.dewPointTemperature')
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.wind.directionTrue')
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.wind.directionMagnetic')
+    delta.updates[0].values.should.contain.an.item.with.property('path', 'environment.wind.speedOverGround')
+
+    delta.updates[0].values.find(x => x.path === 'environment.outside.pressure').value.should.be.closeTo(1013.2075, 0.0001)
+    delta.updates[0].values.find(x => x.path === 'environment.outside.temperature').should.contain.property('value', 276.25)
+    delta.updates[0].values.find(x => x.path === 'environment.water.temperature').should.contain.property('value', 278.75)
+    delta.updates[0].values.find(x => x.path === 'environment.outside.humidity').should.contain.property('value', 0.4)
+    delta.updates[0].values.find(x => x.path === 'environment.outside.humidityAbsolute').should.contain.property('value', 0.03)
+    delta.updates[0].values.find(x => x.path === 'environment.outside.dewPointTemperature').value.should.be.closeTo(276.55, 0.01)
+    delta.updates[0].values.find(x => x.path === 'environment.wind.directionTrue').value.should.be.closeTo(1.5707, 0.0001)
+    delta.updates[0].values.find(x => x.path === 'environment.wind.directionMagnetic').value.should.be.closeTo(1.4835, 0.0001)
+    delta.updates[0].values.find(x => x.path === 'environment.wind.speedOverGround').value.should.be.closeTo(5.0, 0.0001)
+  })
+
+  it('check for no hickup on empty message', () => {
+    const delta = new Parser().parse("$WIMDA,,I,,B,,C,,C,,,,C,,T,,M,,N,,M*04")
+
+    delta.updates[0].values.should.be.empty
+  })
+
+})