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The data collector captures all NMEA 0183 data transmitted and then uses selected elements to produce a picture of a boat’s performance. Data is aggregated as it is received; creating summary data that combines new information with existing values.

Data points are related to a central time period making it possible to combine and compare a large number of variables at a given point.  Its possible to compare the way the sails are set of the sails with the true or apparent wind speed and the weight of the crew. The same figures can be compared on different days to determine the effects of relatively small changes to the boat’s configuration.

The table below summarizes the data points collected:

 
 

Description

Data


Information about the recording session; date, time period size, boat name

Session Information


The technology collects and summarises for a specified time interval in the range of 1-60 minutes

Time Period


All the NMEA data received during a session irrespective of whether the data is used in calculations

NMEA Data


GPS Latitude and Longitude

GPS Position


Speed of the boat through water

Speed through water


Speed of the boat over the ground

Speed over ground


Apparent wind speed and direction

Apparent wind


True wind speed and direction

True wind


A summary of the averages for the data listed above the given Time Period

Time Period Summary


Calculates Polar data for given true wind speeds and angles based on the data collected during a session

Session Polar Data


Calculates Polar data for given true wind speeds and angles based on the data collected during a session

Session Polar Data


Calculates Boat Polar data for given true wind speeds and angles based on the data collected during the sessions for the boat

Boat Polar Data


Calculates Boat Polar data for given true wind speeds and angles based on the data collected during the sessions for the boat

Boat Polar Data


Boat configuration items are customisable, for instance: current sail area can be recorded. The level of detail collected will depend on the information recorded about a boat

Boat Configuration


Distance and heading to a defined way point are calculated and recorded

Route Information


The following summary data points are held for each predefined time interval:

Description

Summary Data Point


The average true wind speed in knots during the sample period. For instance if there are 5 MVW relative wind speed sentences in a given time slot the program will average them out and convert the value to a true wind speed.

Average true wind speed in knots


The average water speed, expressed in knots, in the time period based on the NMEA VHW sentence. Where the NMEA data is only being supplied in KPH or metres per second the software will convert the data.

Average speed through the water in knots


The average apparent wind speed in knots based on the MVW Relative wind sentence.

Average apparent wind speed in knots


The average speed over the ground, rather than through the water, derived from the NMEA VTG sentence.

Average speed over the ground in knots


The average true wind relative to the bow. Figures are 0-180 and should be read in conjunction with the Tack data point taken from either the NMEA MWV Relative converted figure or the NMEA MWV True figure where present.

Average true wind direction relative to the bow


This average combines the NMEA VTG Heading data with the NMEA MWV data to derive actual magnetic wind direction averaged during the time period.

Average true wind direction degrees relative to magnetic north


The average apparent wind speed relative to the bow taken, as above, from the NMEA MWV Relative or True sentence and converted as required. Data is in the range 0-180 degrees and should be read in conjunction with the Tack.

Average apparent wind direction degrees relative to the bow


The average heading of the boat over the ground, as opposed to the direction the boat is actually pointing, in degrees magnetic taken from the NMEA VTG Sentence.

Average ground speed heading degrees magnetic


Tacking the boat will generate the start of a new sample period either Port or Starboard, calculated from the NMEA MWV Sentence.

Apparent wind tack


Calculated as the apparent wind tack and should normally be the same.

True wind tack


Indicates how efficient a boat is, ie if there is a 10 knot True Wind and the boat generates a speed through the water of 5 knots this will have a ratio of 2. A lower ratio implies less efficiency, hence a boat travelling 10 knots through the water in 10 knots of wind will have a ratio of 1, 20 knots in 10 knots of wind a ratio of .5 and so on

Ratio of true wind speed to water speed


Applies a similar logic as the ratio of true wind speed to water speed but analyses the apparent wind speed compared to water speed.

Ratio of apparent wind speed to water speed


The latitude at the end of the sample period taken from the NMEA GLL Sentence.

Latitude degrees minutes seconds


The longitude at the end of the sample period taken from the NMEA GLL Sentence.

Longitude degrees minutes seconds


The latitude at the end of the sample period taken from the NMEA GLL Sentence expressed as a decimal.

Latitude as a decimal


The longitude at the end of the sample period taken from the NMEA GLL Sentence expressed as a decimal.

Longitude as a decimal


Depth below transducer

The depth in metres of the water below the boat.


Where a fluxgate compass sensor is present on the boats network the current boat heading (as opposed to course over the ground is recorded in degrees.

Boat heading in degrees magnetic


Where data is missing for a time period the system will estimate a reasonable number based on the last known data values. ‘ESTIMATED’ will appear for this data point while the record will show ‘CALCULATED’ when the figures are fully calculated.

Estimated/calculated values indicator


In addition to the predefined values collected from the NMEA data an unlimited number of boat configuration variables can be recorded via the boat configuration screens. This makes it possible to record everything from the current sail area to the number of tea bags left in the galley!

After setting the variables the data collector reads the active variables at the start of each time period and records them against the other variables defined in the table above.

As an example, if a boat starts sailing with a large No 1 Genoa and Main Sail these would be recorded as ‘active’. If the wind then gets up and the decision is made to reduce the sail area, this can be recorded by amending the data on the screen and the data collector will record the updated configuration at the start of the next sample.

Given this information its possible to determine the expected boat speed given sail plan A and wind speed B.

 

Interface Connections


The NMEA Data Collector software listens on a number of different types of network interfaces and captures information from various NMEA 0183 data sources:

  • COM Interface – probably the simplest and most reliable solution using a cable plugged directly into either the PC’s COM or USB port with USB-COM converter cable attached.

  • TCP/IP Interface – the standard network protocol which listens to a port on a server type device such as the Digital Yacht WLN10 wireless NMEA 0183 data transmitter.

  • UDP Interface – a less commonly used network protocol more suitable for collecting NMEA 0183 data generated by another software package

  • JDBC Database Access – the program will also load data from a database source making it possible to load and re-process data collected elsewhere or at another time.

 
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Output To Other Software Packages


The Data Collector is able to export the collected and summarised data in csv format. These files can then be uploaded to spreadsheet programmes such as Microsoft Excel for further analysis.

 
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The Data Collector will export the following data sets to .csv files:

  • Collected NMEA with additional source and timestamp information.

  • Summarised data points in either rowise or columnwise format.

  • Columnwise gives a row for each summary data point with the time dimension in each column.

  • Rowise creates a row in the file for each timeslot with the different datapoints in the columns.

  • Polar data set for the current session.

  • Polar data set for the comparison session.

The Data Collector will also export a track to a .kml file. This can be uploaded to Google Earth to display a visual representation of the course that the boat has followed. The basic track is supplemented by key metrics showing the boats performance at each sample point.

 
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