Calculators on questeria.info
I am a retired software engineer and this website is one of my hobbies. One day, while boating on the ICW, I wanted to know when I would arrive at a certain mile marker. In my head, I remember that distance = time * speed and derived that time = distance/speed. But my speed is in knots and my distance is in statute miles. So, I need to convert statute miles to nautical miles by dividing by 1.15. I thought it would be nice to have app on my phone and I decided to write it myself.
So, the Distance Time Speed (DTS) calculator was born. After that, I created a Location Distance Bearing (LDB) calculator.
Another hobby of mine is weather, so I created a Wind Speed from Isobars (WS) estimator and True Wind (TW) calculator. Finally, I created an Apparent Wind (AW) calculator.
I created the calculators using HTML and JavaScript. I made them so you can add the calculators to the home screen of your phone or tablet, to use like an app. The calculator is cached to your device for offline use. If a new version is available, you will get popup that says “A new version of this site is available. Load it?”. Click OK to update the calculator on your device.
Apparent Wind Calculator
After I created the True Wind calculator, I wanted to check it with an apparent wind calculator. I looked and couldn’t find anything that did what I needed. Besides checking my True Wind calculator, I thought it would be useful to see if it is possible to sail in a specific direction with a forecasted wind speed and direction. So, I decided to write my own.
There are four parameters needed:
- True Wind Speed, in knots
- True Wind Direction, in degrees (true)
- Boat Speed, in knots
- Boat Heading, in degrees (true)
Enter the values and press Calculate Apparent Wind and the calculator displays Apparent Wind Speed, in knots and Apparent Wind Angle in degrees.
Distance Time Speed Calculator
The Distance Time Speed calculator was my first calculator. You can use it as a web page drop down or as a standalone web page. You can add the URL of the standalone web page to your phone or tablet home screen, to use like an app. I wrote the first version in Perl and it ran on the server. Later, I rewrote it in JavaScript, so it runs on your device. It is cached on your device the first time you use it, so you can use it when offline.
The calculator performs several calculations and conversions. There are three parameters, Distance, Time, and Speed. You enter two values to calculate the third. You can convert between Nautical Miles and Statute Miles. You can convert between Knots and Miles Per Hour. You can send the Distance value from this calculator to the Location Distance Bearing calculator.
The calculator uses cookies to remember the last values. The values will stay the same until overwritten or cleared with Reset. After that you only need to change one value to calculate a new value. To calculate a new Time, you change either Speed or Distance. If you want to calculate a new Speed or Distance using the same value of Time, you must blank-out Speed or Distance. To calculate a new Distance, using the same value of Speed you specify a new Time. To calculate a new value of Speed using the same value of time you must blank-out a Speed field.
Convert between Nautical Miles and Statute Miles
Enter a numeric value in Nautical Miles field to convert to Statute Miles, or enter a numeric value in Statute Miles field to convert to Nautical Miles. Press Submit to convert.
Convert between Knots and MPH
Enter a numeric value in Knots field to convert to MPH, or enter a numeric value in MPH field to convert to Knots. Press Submit to convert.
Calculate Time using Distance and Speed
- Enter Distance in the Nautical Miles or Statute Miles field.
- Enter Speed in Knots or MPH field.
- Blank-out Time in HH, MM and SS fields.
- Press Submit to calculate Time.
Calculate Speed using Distance and Time
- Enter Distance in Nautical Miles or Statute Miles field.
- Enter Time as hours, minutes, and seconds in the HH MM and SS fields.
- Blank-out Speed in Knots and MPH fields.
Press Submit to calculate Speed.
Calculate Distance using Time and Speed
- Enter Time as hours, minutes, or seconds in the HH MM and SS fields.
- Enter Speed in Knots or MPH field.
- Blank-out Distance in Nautical Miles and Statute Miles fields.
- Press Submit to calculate Distance.
Send to Location Distance Bearing Calculator
Click Send to Loc Dist Brg Calc to bring up the Location Distance Bearing Calculator with the Nautical Miles value from this calculator.
Location Distance Bearing Calculator
The Location Distance Bearing Calculator was the second calculator that I created. You can use it as a web page drop down or as a standalone web page. I wanted to calculate the distance and bearing between two locations or find a location using a distance and bearing from a location. Later, I added the ability to Set Current Location from the device and display/convert different formats of latitude and longitude.
I designed this calculator to use with the Distance Time Speed calculator so you can easily calculate time or speed between two locations.
It uses cookies to remember the last values. The values will stay the same until overwritten or cleared with Reset. After that you only need to change one value to calculate or convert values. To calculate new Distance and Bearing values using one of the same locations change the other Latitude or Longitude value. To calculate new Location 2 values, change a value of NM, Feet or Bearing. Blank-out the Location 1 Latitude and Longitude values to calculate new Location 1 values.
You can send the distance value to the Distance Time Speed Calculator.
You can enter Latitude and Longitude values in many formats. You can copy and paste from other programs such as Google Earth.
This calculator loads to your device for offline use. You can add it to the home screen of your phone or tablet and use it like an app.
Set Current Location
Press Set Current Location to set Location 1 to current position. You might get a prompt saying “http://questeria.info” Would Like To Use Your Current Location. If so, click OK.
Note: Set Current Location requires the calculator be a secure page. If you don’t see a Set Current Location button, try accessing the page from https://questeria.info/ldb/index.html. Location services must also be enabled and supported by the device.
Calculate Distance and Bearing using two Locations
- Enter Location 1 Latitude. You can enter it as a raw number (positive is North, negative is South) or in N or S degrees minutes (Ndd mm.mmm) or N or S degrees minutes seconds (Ndd mm ss.ss). Leave a space between degrees, minutes and seconds. You can also paste in a location like Ndd°mm’ss” from another application, or even a latitude/longitude pair like, 28°34′15″ N 83°11′41″ W.
- Enter location 1 Longitude. This is like entering latitude, except that East is positive and West is negative.
- Enter Location 2 Latitude
- Enter Location 2 Longitude
- Blank-out NM, Feet and Bearing fields.
- press Submit to calculate distance and bearing.
Calculate Location using Distance and Bearing
- Enter a latitude in Location 1 or Location 2.
- Enter a longitude in Location 1 or Location 2.
- Blank-out the Latitude and Longitude fields you want to calculate.
- Enter a distance in NM or Feet, and blank-out the other field.
- Enter a Bearing.
- Press Submit to calculate Location 1 or 2.
Swap Locations 1 and 2
Press Swap to swap Location 1 and Location 2. This is useful when you want to set Location 2 to the last current location before getting your new current location.
Convert between Nautical Miles and Feet
Enter a numeric value in NM field to convert to Feet, or enter a numeric value in Feet field to convert to Nautical Miles.
Convert between Lat/Lon formats
- Enter latitude and/or longitude into Location 1 and/or Location 2 in any valid format.
- Select one of three Lat/Lon formats:
- dd mm.mmm (Degrees and Minutes)
- dd mm ss (Degrees, Minutes and Seconds)
- dd.ddddd (Decimal Degrees, E and N are positive, S and W are negative)
- Press Submit to display Location 1 and Location 2 in the selected format.
Send to Distance Time Speed Calculator
Press Send to Dist Time Speed Calculator to pass the Nautical Miles value to the Distance, Time and Speed calculator.
True Wind Calculator
I created the True Wind Calculator after reading Modern Marine Weather: From Time Honored Maritime Traditions to the Latest Technology, by David Burch. You use it when you want to calculate true wind while moving. Some wind instruments can do this automatically if connected to a GPS to measure boat speed and boat heading. Use this if you want to watch true wind and yours doesn’t.
There are four parameters needed:
- Apparent Wind Speed, in knots
- Apparent Wind Angle, in degrees
- Boat Speed, in knots
- Boat Heading, in degrees (true).
The calculator gives you True Wind Speed, in knots and True Wind Direction, in degrees (true).
Estimate Wind Speed from Isobars
The Wind Speed from Isobars estimator is another calculator I created after reading Modern Marine Weather: From Time Honored Maritime Traditions to the Latest Technology, by David Burch.
This estimator estimates wind speed using isobar spacing, from a weather map or fax. I use a digital micrometer to measure the distance on my Android tablet.
To use the Wind Speed Estimator:
- Enter the Isobar Space. This is the space between isobar lines on a weather map or fax. The units of measurement are unimportant as long as they are the same units of measurement used for Latitude Space. (I use a digital micrometer.)
- Enter the Latitude Space. This is the space between latitude lines. Use the same unit of measurement used for Isobar Space.
- Enter the Latitude in degrees, to a tenth, such as, 24.4.
- Enter the Number of Isobars. This is the number of isobars between isobar lines on the map. It is usually 4, but sometimes it is 2.
- Enter the Number of Degrees. This is the number of degrees between latitude lines on the map. It is usually 10, but sometimes 5.
- Select an air mass stability. The default is average.
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The estimator determines surface winds from a balance between pressure gradients, Coriolis forces and frictional drag on the surface—a factor that depends on the air stability. If you have reason to believe the air mass is more or less stable than average, you can specify it with this option. Generally, air within a High or within the warm sector of a frontal wave is stable, which would lead to less wind speed for the same gradient. - Press the Estimate Wind Speed button (or press enter) to display wind speed.
This application is cached in your device so you can run it when you are not connected to the internet. You can also add it to the home screen of your phone or tablet for easy access.
Note: This estimator assumes straight isobars.
Isobar Curvature Correction
| V²/R | Correction |
| <25 | none |
| 25-50 | 5% |
| 50-100 | 10% |
| 100-200 | 15% |
| 200-300 | 20% |
| 300-400 | 25% |
| 400-600 | 30% |
| 600-1000 | 40% |
| 1000-1500 | 50% |
| >1500 | 60% |
The estimator assumes straight isobars. You can use the above table to account for centrifugal force. V is the wind speed, in knots, from the estimator and R is the radius of the curve in degrees of latitude. Calculate the ratio V²/R to find the correction factor. The correction diminishes winds around a low, and increases winds around a high.
From Modern Marine Weather: From Time Honored Maritime Traditions to the Latest Technology, 2nd Edition by David Burch
Using the Calculators
These calculators can be used on a phone, tablet or computer. I mostly use them on my iPhone. To set them up the first time, go to the Utilities page and click on each link. Add it to your home screen. On iOS, click the square with the up arrow on the bottom of the screen, and then click Add to Home Screen. On Android click the three dots in the upper right side of the screen, and then click Add to Home screen. A clickable icon is added to your home screen. The calculator is loaded on your device, so you can use it even when offline. If there is an update to the calculator, you will get a message asking if you want to load it.
I group all five calculators in a folder. To create a folder on iOS or Android, press and hold an icon and move it onto another icon. Then press and hold each icon and move it onto the folder. Now I can quickly open my folder and open a calculator on my phone.