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Getting Started with the DashBoard

Table of Contents

Overview and Description

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The goal of this document is to get you started with the DashBoard, and the way to use and take advantage of the analysis features it provides. This is presented as a tutorial. The objective is not to teach you everything about it, it is to show a possible path to achieve the logged data analysis. We will walk you through one of the possible path to do so, and this is more than probably not the only one...
We will describe here the way to analyze the data logged during a sailing. The way to log the data is described in another document.
The scenario is the following one:
You're back from sailing, and you've logged some data. You brought home the computer you logged data with, now what?

Installation

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If you're back from sailing, and have logged some data, it probably means that you've already installed the DashBoard, as described in the installation document.

Getting Started

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Even if you've not logged data yet, we provide with the DashBoard some sample data you can use to get used to the way to work with the DashBoard... We are going to use one of those samples in this demo.

Section Content

Importing Data

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Once data have been logged and prepared to be displayed in the DashBoard, they have to be imported, as shown in this viewlet.

Available options to display

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Once data are imported and visible in the top left panel, several types of informations are available, and you might want to display and visualize them.
Mostly, informations are driven by the focus in the top left panel.

Segmenting a file

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A file visible in the top left panel can be segmented into several smaller segment, for a more precise analyse.

Statistics

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Different kind of statistics can be displayed, and they're available from different panels.

Marks, notes, comments

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A file, a segment, a chart, can be annotated.

Drifting: Tide and Leeway

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This is a very important part. To actually be able to see - and use for further analysis - what the boat was doing while we were logging data, we need to compute the leeway of the boat. The main data returned by the instruments to calculate it are

To the heading, we must add or substract the leeway, to know what the actual route over the water was.

To this route over the water, the potential current vector is combined to the surface route vector to return the course and speed over the ground.

No accurate calculation of the tide can be done before we know what the route over the water was, which means that all this calculation depends on the accuracy of the leeway computing.

Leeway
We assume in this diagram that the wind comes from port.

We will consider that the leeway is an angle. As opposed to the current, which is a vector.

The current is pretty easy to calculate, it's the difference between the position returned by the dead reckoning and the one returned by the GPS.
All the difficulty comes from the fact that the dead reckoning has to be calculated with the surface route, which involves this leeway angle...
More information about the way we calculate the leeway can be found here, in the "Calculate Leeway" section.
But this is just the beginning, the theorical part... The function described in this document returns a value that has to be tweaked after the real conditions, which mainly involve parameters depending on:

And, last but not least, we must have an accurate reading of the boat speed. Refer for more details to this document.
To help this calibration process, the DashBoard provides the possibility to apply a coefficient on the values read during the logging.

To clearly explain all this, let us take concrete examples. A first interesting one will show the way we manage the data logged on May 31st 2003, on the Berkeley Circle.
This day, the sea was not oriented in the wind, generating a different leeway on both tacks. It was also quite choppy out there, generating more leeway than usually.

We will see how to elaborate the leeway factors, obtaining by the end a constant reading of the current, even when tacking or rounding a mark.
We will assume that the segmentation of the data file has been done already. Let's display the course of the first race, and let's draw the current on the chart. We should obtain this:

First try

As it can be seen, this display is probably wrong! It is very unlikely to have the current changing its direction exactly when the boat tacks or jibes! (see around the D mark)
Also, when tacking upwind (top part of the diagram), the current not only changes its direction, but also its speed, from one tack to the other. The waves were this day oriented at the left of the wind. We were almost facing then on starboard tack. Using the Leeway Factor feature of the DashBoard, we are going to try to fix that.
Menu Item
Right-click on the file, or on the segment, and choose the appropriate menu item.
Dialog Box
Values are set to 1.0, neutral element.

We want to change those values, as follow:

New values

Saving those values and redisplaying the chart will show something closer to the reality.

New Display

As it provides some smoothing capabilities, the current shift panel can confirm.

Current Shift

A similar process was applied to the data logged on June 7th 2003, when rounding Southampton Shoals. We were going north with the spinnaker, and came back south after dropping it around the mark, leaving it to starboard.

Before correction
Before correction

Values
New values

After correction
After correction, much better

Prediction

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We also provide a mode to calculate the best route after a given true wind direction, a start, and a destination.

Report a bug, or request an enhancement

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Please, tell me!


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