MeanSeaLevel = 0.5

Citizen.CreateThread(function()
    while true do
        Citizen.Wait(0)
        local PlayerRef = GetPlayerPed(-1)
        if (IsPedSittingInAnyVehicle(PlayerRef)) then
            local PlaneRef = GetVehiclePedIsIn(PlayerRef, false)
            local PlaneX, PlaneY, PlaneZ = table.unpack(GetEntityCoords(PlaneRef))
            local Altitude = GetEntityHeight(PlaneRef, PlaneX, PlaneY, -MeanSeaLevel, true, true)
            -- Basically the same as PlaneZ + MeanSeaLevel buuuuuuuuuuuuuuuut oh well
            drawTxt("ALT (meters): " .. roundInt(Altitude, 1) .. " (feet): " .. roundInt(Altitude * 3.28084, 1))
        else
            drawTxt("ALT: No Data")
        end
    end
end)

function roundInt(num, numDecimalPlaces)
  local mult = 10^(numDecimalPlaces or 0)
  return math.floor(num * mult + 0.5) / mult
end

function drawTxt(text)
    SetTextFont(0)
    SetTextProportional(1)
    SetTextScale(0.0, 0.3)
    SetTextColour(255, 255, 255, 255)
    SetTextDropshadow(0, 0, 0, 0, 255)
    SetTextEdge(1, 0, 0, 0, 255)
    SetTextDropShadow()
    SetTextOutline()
    SetTextEntry("STRING")
    AddTextComponentString(text)
    DrawText(0.005, 0.005)
end