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[帆译作品] 掌舵航行APP概括Review of "Course to Steer" App

发表于 2015-5-4 20:51 | 显示全部楼层 |阅读模式

Review of "Course to Steer" App
 掌舵航行APP概括Review of "Course to Steer" App 1.jpg

The "Course to Steer" boatingapp has particular value for sailors whose relatively slower speed through thewater is easily affected by tidal currents and the leeway of the boat in thewind. When these factors throw the boat off its ideal course straight to awaypoint or destination, experienced sailors have always learned to steer moreto one side or the other to compensate (and to avoid obstacles toward which thewind or current may move them).
We can tell youwhich side to steer to, you need trigonometry to calculate the actual course tosteer in order to stay on the direct shortest path to the destination.
Most of us can'tdo trig that quickly in our head, and most chartplotters don'tcalculate that. But the free Course to Steer app does the work for us.
Versionreviewed: 1.5c
Available on Android Google Play Store - free (at time of testing)
Tested on Lenovo A1 Tablet running Android 2.3
What It Does它能做什么
"Course to Steer" is arelatively simple app that essentially does one thing only: when you input theappropriate variables about your boat, your course, and other factors, itcalculates for you the exact optimal course to steer to stay on the direct lineto your destination or waypoint - the best course over the ground (COG). Withit you can avoid what is often called cross-track error (the deviation fromyour intended course), which results from a current or wind taking you offcourse.
It also calculates your true speed overthe ground (SOG) regardless of what your boat's knotmeter may tell you aboutyour speed through the water.
We create apps in any language. Call us on+44 7762 59 54 38
Once you gothrough the initial learning curve, the app is very fast and easy to use. Hereare the steps in which the user typically enters data:
我们开发多种语言版本的APP,联系我们请拨打+44 7762 59 5438
1.   Ground track - the direction you want to go (in true, notmagnetic, degrees)
2.   Tide direction - the direction in which a tidal or othercurrent is moving (in presumably true degrees)
3.   Tide rate - current speed in knots
4.   Boat speed - through the water in knots
5.   Wind from - direction from which the wind is coming(choose among 8 directions, or none)
6.   Leeway - entered in degrees (may be confusing at first -see comment below)
7.   Magnetic variation - the variation of local magneticdirection from true direction (enter this in degrees W or E - from your localchart)
8.   Magnetic deviation - presumably a deviation factorrelated to your boat's compass
Then tap the"calculate" button to receive the following information:
·        CTS true - course to steer (or intended course overground, COG) in degrees true, not magnetic
·        CTS magnetic - course to steer in degrees magnetic
·        CTS compass - course to steer in degrees magnetic usingyour compass (if you entered a deviation number previously for your boat'scompass)
·        Speed over ground - your actual SOG along the COG
·        真实CTS数据——掌舵航行的真实数据,而非磁场概念上的数据
·        CTS磁场——掌舵航行的磁场信息
·        CTS指南针——掌舵航行的利用船上的指南针生成的方向信息(前提是你已预先设定的磁偏差)
·        航行速度——整个航行中真实速度
Why This Matters 为什么这个APP这么重要
Even just playing around with this appalmost immediately helps you improve your understanding of wind and current onyour actual course over ground. It's very easy to be way off in your own commonsense calculations. For example, imagine you are sailing due north in a verylight wind, going only 2.5 knots. From due west is a 2-knot tidal currentsweeping you east. You know you need to turn westerly in order to reach yourdestination - but how far to the west? If you like math puzzles, take a guessbefore reading the next paragraph.
I might haveguessed that you'd have to turn maybe 40 degrees toward the wind to compensatefor the current, to a heading of around 320. In reality, because this is atrigonometric function, you have to turn 53 degrees to a heading of 307 - justto be able to make a COG of 360. But with the wind from 270, you can't sail atthe point of sail of 307, soyou'd have to do some tacking. That means youbetter be aware of possible underwater hazards well off to both sides of yourideal course or run some significant risk. That's a lot to have to payattention to, but at least this app helps keep you from making blindassumptions about how to sail to maintain the clear straight course to yourdestination.
The Downside缺点
As far as I havebeen able to test it, the app does seem to make its calculations correctly. Onthe water, of course, every boater should be constantly aware of boat positionat all times anyway, such as with a navigation app that showsyour boat's position against a chart - so it would be dangerous to trust"Course to Steer" or any other app to keep you free of underwater orother hazards.
My onlycomplaint is that the app in this version has no help screens at all and savesno settings. While for the most part you could view this as just a fancycalculator, to use it well you need to understand the concept of leeway to beable to enter that data into the app. Leeway is the degree of movement of theboat off course due to wind. If the wind blows hard from the west as you travelnorth, for example, then your boat's track will vary from a line straight aheadoff to easterly. How much leeway you experience depends on both how hard the windis blowing and how much wind your boat "catches." A boat with highfreeboard generally has more leeway than one with low, and leeway increaseswith wind speed. In the app, however, you enter only a number for your boat'sdegree of leeway along with the wind direction (but not speed). So to do thiswell, you have to estimate, for different wind speeds, how much leeway your ownboat experiences. For an app that otherwise seems so precisely mathematical andaccurate, this estimate could throw your results off considerably if you guesswrong. I would urge the app developer to think about this and perhaps offersome advice for how one should do this estimating. Perhaps you could calculateyour usual leeway from using other GPS data commonly available in other navigationapps?
Overall, this is a nice little app thatboaters should consider using. As a free app, it's nicely not cluttered withads or requests to update to a paid version. (Hopefully it will stay that way.)Just remember that because of the leeway function, your own results could varyfrom the predicted results. And even if your results are correct, you may haveto make other changes in navigation, such as in the tacking example earlier.
If you use a regular navigational app orchartplotter instead of this app, you can still easily learn to compensate for currents.


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发表于 2015-5-4 23:19 | 显示全部楼层
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发表于 2015-5-5 00:19 | 显示全部楼层
 掌舵航行APP概括Review of "Course to Steer" App
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发表于 2015-5-5 00:20 | 显示全部楼层
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 楼主| 发表于 2015-5-5 11:31 | 显示全部楼层
myadmin 发表于 2015-5-4 23:19  掌舵航行APP概括Review of "Course to Steer" App

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 楼主| 发表于 2015-5-5 12:32 | 显示全部楼层
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发表于 2015-5-18 20:16 | 显示全部楼层
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