Important Information

There are a number of things that are important to know

Coordinate Formats

SearchWell uses DECIMAL DEGREES for doing the calculations, but it accepts input in any of the three major formats - Decimal Degrees, Degrees and Decimal Minutes or Degrees, Minutes and Seconds

The coordinates can include the official coordinate symbols of

•° - to indicate degrees

•'  - to indicate minutes

•"  - to indicate seconds

•S or N to indicate which hemisphere

•E or W to indicate East or West

If the symbols for degrees, minutes or seconds are not used, then type a space in their place - as follows

•Decimal Degrees : -34.38654°, 018.83764°   or  -34.38654, 018.83764

•Degrees and Decimal Minutes : 34° 25.872'S, 018° 43.876'E  or  34  25.872 S, 018  43.876 E  or  -34  25.972, 018  43.876

•Degrees, Minutes and Seconds : 34° 50' 34"S, 018° 24' 38"E  or  34  50  34 S, 018  24  38 E  or  -34  50  34, 018  24  38

The rule is that the Latitude must be separated from the Longitude by a comma.

Buttons on forms

We have a standard for buttons on all SearchWell forms - 

Green, Orange, Purple and Light green information boxes

A typical screen in the system looks similar to the above .... there is color coding

•A : Green background - this information is compulsory, and you will be prompted for it if it is not given or if it does not appear to be valid

•B : Light green background - this information can be given, but it is not compulsory

•C : Purple background - this information is compulsory but contains a default value that can be changed if required

•D : Orange background - the user cannot edit these items but can copy them.  They are where SearchWell will display information it has calculated or information that is being stored in the system

Time input

Whenever a time is input the following rules must be followed - 

1)The 24 hour clock is used, to 2pm will be entered as 14:00

2)When a time after midnight is entered eg 15 minutes past midnight, it must be entered as 00:15

Leeway Table

The table defining the formula to be used when calculating the effect of the wind on a drifting casualty is based on Allen & Plourde’s 2005 study and recommended by the IAMSAR (International Aeronautical and Marine Search and Rescue) in 2016.  It includes items being used by various international marine rescue organisations.  See Leeway Table for the table.

Points Table

SearchWell offers you the ability to capture and save information about points in your operational area (land and sea) that you refer to often.  This information can then be used throughout SearchWell any time coordinates of a location are required.

•A : The light green box is optional, and is where you can type in a keyword on which to filter the points shown to you in the list marked B.  The filter word is not case sensitive, and so typing "cape" as in this example will pick up any point with Cape or CAPE in it's name.  Then, the word can be in any position in the name of the point - so, "Cape Point" will be selected as will "Black Rocks (Cape Peninsula)" be selected.  The important thing is that once you have typed your filter word you MUST press enter to activate it.

•B : The points that are stored in the Points Table.  If you have not used the filter marked A, than all the points in the table are displayed, but if you have used the filter as shown in the above diagram, then only points with the word "cape" are available to choose from.  

•C : Once you have selected a point in the list described in B by clicking on it, the coordinates associated with the point will be displayed in the Coordinates box.

Probability and confidence in the information that is given during the Datum calculation

New to Version 5 of SearchWell is the concept of confidence levels and the calculation of the Probability of Detection of a casualty.

When we use the Condition Forecast and Leeway table as the method of calculating a Datum position, the accuracy of the result depends upon the accuracy of the following input information - 

Confidence Levels

•LKP position

The confidence you have in the LKP Coordinates will depend upon where the information came from.  If there was one person who saw the casualty and estimated the position, you will be less confident in the information than if the coordinates came from a GPS location pin or a system like SafeTrx.

SeachWell offers the following confidence levels 

oat the given LKP

oGPS/AIS (0.1nm)

oVisual description (0.5nm)

oVisual Fix 3 lines (0.5nm)

oRadar (0.5nm)

oCelestial Fix 3 lines (2nm)

oGUESS (3nm)

The default setting is that the casualty was somewhere within 0.5nm, in any direction, from the coordinates you are using

•Divergence from the Leeway table

The Leeway table gives a divergence angle for each casualty type ..... experimentation and observation have shown the objects can diverge to the left or to the right of the force pushing them depending upon the condition of the object - this is the divergence.  For our random points we offer a random divergence using an angle between the left-most and the right-most divergence.  For instance, in the Leeway table SearchWell uses, a yacht has a divergence of 48° ..... and so when we calculate our random points the divergence angle will be anything between -48° and +48° from the wind push.

•Forecast conditions

The options are as follows 

An example of what this means - if your forecast conditions talk of a 10 knot wind with a bearing of 270°, and a 1 knot current with a bearing of 100°

When you select a Moderate confidence in both, the randomiser will use 

oa wind speed between 8 knots and 12 knots (20% on either side of the 10 knot forecast)

oa wind bearing between 255° and 285° (15° on either side of 270°)

oa current speed between 0.8 knots and 1.2 knots (20% on either side of the 1 knot forecast)

oa current bearing between 80° and 120° (20° on other side of the forecast current bearing)

•Drift from a test drift

The information that can vary from the test drift

othe divergence from the path taken by the object drifted

othe speed of drift compared to that of the object drifted

  

Random Probability

SearchWell uses the above confidence levels and calculates a Datum position for each of the number of Random Points (given during the Datum calculation).  The calculation is the same as that using the user given information that results in the Datum position, but it applies a random LKP position that is within the given confidence level, and uses a random wind speed, wind bearing, current speed and current bearing (all within the limits of the selected confidence level).

Doing this results in a number of random points that follow their own paths and end up in a slightly different position from the other points depending upon the random information used.

In the graphic above, 

•A : the yellow line is the calculated drift path of the casualty using the information given by the user  

•B : the thin white lines are examples of the paths followed by selected random points

•C : The description of a random particle which is displayed when you click on a particle

•D : The random LKP points

•the small colored circles are the Datum positions of 1000 random points.  The color coding of these random points is - 

ored circles are the points within a 15% of the maximum distance from Datum of the furthest random particle

oorange circles are 16% to 30% of the maximum distance from Datum

oyellow circles are 31% to 45% of the maximum distance from Datum

ogreen circles are 46% to 60% of the maximum distance from Datum

ocyan circles are 61% to 80% of the maximum distance from Datum

opurple circles are 81% to 100% of the maximum distance from Datum

•the cluster around the LKP show the random LKP points

Also see Probability Output in the Datum section

Downloading Condition Forecast information

It is important to remember that Forecasts are well researched GUESSES as to what the wind and the current (and other variables) will be doing - they should not be considered absolute nor factual.  This is particularly true for current forecasts as the movement in the sea is very hard to predict in detail.  

The best process is to confirm the ocean current using a TEST DRIFT in the area  and then to compare this with the forecasts.  A test drift should only be done if the following aspects are considered - 

oas soon as it possible after the casualty was thought to be in the area

oas close is as possible to the position the casualty was thought to have been

ousing an item as similar as is possible to the casualty object ...... our drift buoys drift in a similar way to a person in the water

These forecast models have been researched and developed independently of each other, and give results that differ from each other to varying degrees.

Windy.com has been the "go to" source of forecasts for many - they offer wind from GFS and from ECMWF, but they only offer currents from Copernicus.  

That said, most often the forecasts SearchWell downloads are not exactly the same as those shown on Windy.com. 

By way of trying to explain why - 

•these models update their information 4 times a day.  SearchWell looks for and uses the latest available information - so we might download from a different file.

We are trying to find out whether or not Windy.com uses the same 'definition' forecasts as we have access to.

SearchWell offers to download from two sources

•EUR - The main European source downloading 

oWind from ECMWF

oCurrent from CMEMS (Copernicus)

•USA - the main USA source downloading

oWind from GFS

oCurrent from HYCOM

These options are available in both the Datum section and the Forecast section.

Forecasts downloaded from European sites appear to take a bit longer to download than those from America ......  most often one waits a minute or so depending upon the amount of information being downloaded.

Saving files from the system

All the files that are output by SearchWell will be stored on the C: drive on the computer in a folder called C:\SearchWell Output Files\.  

Then, a sub-folder is created within this folder with the name structured as follows - Date and Description eg. "2024-09-05 Search Output Files" or "2024-09-05 Condition Forecasts" depending upon whether the file contains information calculated by SearchWell of the downloaded forecast condition.

So the full path of a file 

ocreated by SearchWell on 2024-09-05 would be "C:\SearchWell Output Files\2024-09-05 Search Output Files\" 

oany forecasts downloaded on 2025-09-05 would be "C:\SearchWell Output Files\2024-09-05 Condition Forecasts\"

•The system creates 4 types of files – 

a.GPX files which are sent to the navigational device on the Rescue Vessel and contain the information of a waypoint or a route

b.KML files which are imported into a program like Google Earth to copy what is in the GPX file (but with a nicer looking preview) and to show information related to the random points

c.CSV files which are used to store the detailed information used in some of the more complex calculations.  These files can be opened in a spreadsheet

d.NC files which store the condition forecast information and are read by SearchWell

  

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