distance & bearing

function getUnitPos(unitName)
  local unit = Unit.getByName(unitName)
  local unitPos = nil
  if unit ~= nil then
    unitPos = unit:getPosition()
  end
  return unitPos
end

function getDistance(unit1, unit2)
  local dist = nil
  local pos1 = getUnitPos(unit1)
  local pos2 = getUnitPos(unit2)
  if pos1 ~= nil and pos2 ~= nil then
    local px = pos1.p.x
    local pz = pos1.p.z
    local zx = pos2.p.x
    local zz = pos2.p.z
    dist = math.sqrt( (px - zx)^2 + (pz - zz)^2 )
  end
  return dist
end

function getBRA(unit1, unit2)
  local BRA = nil
  local pos1 = getUnitPos(unit1)
  local pos2 = getUnitPos(unit2)
  if pos1 ~= nil and pos2 ~= nil then
    local px = pos1.p.x
    local pz = pos1.p.z
    local zx = pos2.p.x
    local zz = pos2.p.z
    local dx = zx - px
    local dz = zz - pz
    BRA = math.atan2( dz, dx ) * 180 / math.pi
    if BRA < 0 then
    BRA = 360 + BRA
    end
  end
  return BRA
end

local dx = zx - px
    local dz = zz - pz
    -- http://stackoverflow.com/questions/1311049/how-to-map-atan2-to-degrees-0-360
    dir = math.atan2( dz, dx ) * 180 / math.pi
    if dir < 0 then
      dir = 360 + dir
    end

local dist = getDistance("Pilot #1", "Pilot #2")
trigger.action.outText('Distance: ' .. dist, 5)
local BRA = geBRA("Pilot #1", "Pilot #2")
trigger.action.outText('BRA: ' .. BRA, 5)