Track Spacing Question???

[snakecharmer]

I'm pretty new to ES ... and this weekend I was working as a MSA during a SAREX.  I was sitting in on an aircrew briefing and they were getting ready to fly route search ... using 1 mile track spacing.  When I asked why 1 mile track spacing I was told only "It is always that way" .... Why 1 mile? Why not 2 miles or 1.5 miles or .5 miles?   

[RiverAux]

There are of course a lot of alternatives, but through decades of experience 1 mile track spacing is a reasonable compromise that allows you to cover the most territory while still having a reasonable probability of detection.

Now, if you have a relatively small area where you know the target is, then you might want to go down to 0.5 miles. 

Of course, things are different in the mountains....

[PHall]

I'm pretty new to ES ... and this weekend I was working as a MSA during a SAREX.  I was sitting in on an aircrew briefing and they were getting ready to fly route search ... using 1 mile track spacing.  When I asked why 1 mile track spacing I was told only "It is always that way" .... Why 1 mile? Why not 2 miles or 1.5 miles or .5 miles?   

Track spacing depends on a number of variables such as the aircraft's height above the ground, the amount of vegetation on the ground, visibility from the aircraft, type of terrain (i.e. flat or mountains or something in between) and the speed the aircraft is flying among other things.

[RiverAux]

I will say that if a unit has gotten in the habit of "always" doing 1 mile, they've gotten in a dangerous rut.  It may often be the best choice, but it shouldn't be automatic. 

[heliodoc]

In some areas and again it depends on where everyone is located

Here in the Midwest ....section lines are 1 mile squares...that was the rumors I always heard and it was easy to follow

Coverage was "fairly easy" to do...but that was GOB's telling me...nothing too scientific

[Short Field]

Track Spacing is one of several variables using in determining Probability of Detection during a search.  Chapter 11 of the Inland SAR Planning Coursebook covers it fairly well.  I am not sure where the document is located on-line.  There are also other sources that could be used.  I think the bottom line is that the track spacing should be set for each mission based on the variables of that specific mission.   Otherwise you are just using general rules of thumb, not specifics information.  Rules of thumb are ok if that is all you have, but it is not the preferred option.   

[Pingree1492]

Here's a maximum visibility chart for several objects from the air (information was pulled from the NESA powerpoints)

Person in life jacket (open water or moderate seas)   1/2 mile
Person in small life raft (open water or moderate seas)   3/4 mile
Person in open meadow within wooded area              1/2 mile or less
Crash in wooded area                                    1/2 mile
Crash on desert or open plain                                 2 miles
Person on desert or open plain                         1 mile or less
Vehicle in open area                                    2 miles or less

Now, your search visibility (the maximum distance that you can see and recognize the make/model of a car on the ground) is typically going to be about 2-3 miles, on a nice clear day.

Your ability to scan and adequately cover an area on the ground is typically going to be about a mile from the plane or less.

So, because you have a scanning coverage of a mile from the plane per observer, putting your tracks a mile apart gives you good overlap in your search area (thus increasing your POD), and still allows for a reasonable amount of time to be spent in the grid.

So, depending on visibility, if you for some reason launch without a scanner, etc, etc you might want to increase or decrease your grid spacing.  But a mile tends to work really well, and is really easy for us to fly on the planes, due to how the roads were built.

Obviously in the mountains, you'll be doing contour searching, which typically uses 1/2 to 1 mile spacing between contours.  And sometimes less, depending upon the steepness of the slope and the thickness of the trees.  And, you'll probably run a few more tracks, closer together in the areas around commonly traveled passes as those tend to be higher probability areas.