This panel defines all the environmental parameters that impact the external ballistics of a release. Except for wind, the impacts are generally minimal but are included for completeness and to give the archer a feel for the effect. That said, changing altitude by 2000 meters (~6600 ft) will be seen to induce sufficient change to warrant a different sight tape.
The archer's location is used to generate sensible environment defaults primarily air pressure, air temperature and gravity are calculated. From these, secondary parameters such are air density and viscosity are calculated.
Optionally enter your approximate latitude in degrees from the equator. Along with altitude is used to determine default gravity, air pressure, and air temperature for the ballistics calculator. The latitude impact is small and hence not critical, but may still be interesting to observe.
Optionally enter your approximate altitude above sea level. Along with latitude is used to determine default gravity, air pressure, air dynamic viscosity and air temperature. Altitude can have a significant effect on arrow flight due to reduced drag in thinner air.
A fuzzy measure of impact of cloud cover on radiation from the Sun and radiation back to space. To assist in determining Apparent Temperature.
Time of day for Apparent Temperature calculation. Default units are hours since midnight. Allows for calculation of likely solar radiation during the day or cooling at night.
Clicking the Apply Location button will calculate the most likely gravity, temperature and pressure, from which other parameters are calculated. You may override the calculated values with manual entry, but such entries will be lost if this button is clicked again.
This is used to determine the gravitational pull on the arrow during flight. It varies by about ±0.35% over the planet, and is updated by the Apply Location button, but can be manually loaded. It is included for interest only and as it does not change significantly with time, it has little practical importance. There is discernible impact on a sight tape when moving from locations of low to high gravity.
An estimate of the radiation flux heating or cooling the archer. To assist in determining Apparent Temperature.
The Apparent Temperature is the temperature an archer is likely to feel in the environment he is in. It is a function air temperature, humidity, radiation and wind speed. Presently not used, but may be in future for impact on archer's scores.
Choice of air or water. This is the medium through which the arrow passes. The water option is obviously for bow-fishing and assumes it enters the water soon after leaving the bow.
Presently the hydrodynamic arrow model is no where near as precise as the aerodynamic model and is intended only to provide a rough indication of what may happen. Arrow buoyancy is taken into account so gravity is less significant.
Air temperature. It impacts the air density, viscosity and speed of sound. Enter any value between 0 K to 500°C. The optimum modeling range is between 0°C and 30°C, however the wider range may be at slightly reduced precision.
This is the atmospheric pressure. It also impacts the air density and viscosity
Enter the local relative humidity (%RH). Humidity has a small impact on
air density and viscosity. In still sunny conditions, "bubbles" of warmer
humid air can rise from vegetated surfaces and may impact flight.
The calculated dew point is the temperature at which condensation of the
air's water vapor will occur. Arrows below the dew point will become
heavier with the accumulation of condensation . Condensation on bow limbs
may slightly slow and de-tune the bow. For traditional bows, high humidity
can significantly impact the performance of the bow materials after more
extended exposure.
This is the calculated (from pressure and temperature) air density. It can not be entered directly, although the units may be changed in the usual way.
This is the calculated air viscosity. As with air density it can not be entered directly, although the units may be changed in the usual way.
The calculated speed of sound. It is used for estimating the warning time and the strike sound return time. Note: between 0° and 30°C uses a precision calculation based on temperature, pressure and humidity. Outside this range, the precision is reduced.
Wind, particularly cross winds have a big impact on an arrow's flight. Like everything in archery, wind is complicated as it changes direction, speed and turbulence. Further, the wind's characteristics change with height and time of day.
In FlyingSticks, the wind is modeled as a steady air flow with gusting superimposed. The steady flow is used for drift calculations and the gusting for group size enlargement.
The gusting model assumes both the speed and direction vary with time.
Enter the average speed as accurately as possible. Note that as an archer you would usually wait for a lull in the wind to release, so at release the wind is likely to be low than the average. However along the flight path the wind is unknown.
If a negative speed is entered it is converted to positive and 180° added to the wind direction.
Enter the height of the anemometer used for the wind speed measurement. The height is used to adjust for wind gradients with height. The standard height for an anemometer is 10 m (~33 ft) above ground and will read higher and steadier than a ground level measurement, however typically anything goes!
Enter the direction where 0° is a head-wind, 180° a tail-wind, 90° is a cross-wind from the right and 270° from the left. The circular dial to the right of the field gives an indication of the direction, looking from above the dot represents the direction from which the wind is coming. The dial may also be used for setting the direction. Negative directions are converted to the positive equivalent, thus –90° becomes +270°.
If in a sloping terrain, the wind may have a vertical component. Enter a positive value for a wind descending towards the archer, or a negative value for a wind ascending towards the archer.
Wind speed tends to increases logarithmically with altitude, but the rate is dependent on the surface roughness and atmospheric conditions. The surface selection provides an approximation to what may be expected.
The ground topology and cover impact both wind gusting and average wind speed at different heights. Select the option that best suits your location. The model assumes level ground and the "none" optional assumes no gradient i.e. the wind speed is the same at all heights.
Any cross wind will cause an arrow to drift off course. The amount of drift is dependent on the wind speed, direction and arrow drag.
EnableChecking this box will allow the ballistics calculator to consider wind drift in all its calculations. This function is also available in the bottom right area of the calculator window.
The horizontal offset or drift on target associated with wind effects on arrow flight at the current range.
The vertical offset or drift on target associated with wind effects on arrow flight at the current range.
Wind gust is treated separately to wind drift, although it is based on the same basic wind description.
EnableCheck this box to include gusting and the enlarged grouping area will be displayed on target views. This function is also available in the bottom right area of the calculator window.
Most winds vary in strength. Enter the percentage variation here. The figure should be an estimate of the uncertainty. Typically, a target archer would delay release for a lull to reduce the uncertainty. In reality it is not possible to summarize wind gusting into a single figure, however this simple approach is better than nothing!
The gusting is treated independently from wind drift. Wind drift can be compensated for by cantering the bow or offsetting the sight, while gusting effects can not be compensated. Only reducing arrow drag will reduce the gusting impact.
The calculated wind gust induced group width increase. This is added to the user's form group width when the "Include Gusts in Groups" check-box is checked.
The calculated wind gust induced group height increases, usually much smaller than the horizontal term. This is added to the user's form group height when "Include Gusts in Groups" check-box is checked.
Try reducing gravity to that of the moon (G = 1.625 m/s2) and air pressure to zero to see what your flight range would be. Try Venus where G = 8.9 m/s2, similar to Earth, but air pressure is a massive 92 bar.
As one might expect, an arrow entering water will experience very high drag...