Football Field Lighting Calculations
Directory:
1. Football Field Lighting Standards
2. Proper Placement of Venue Light Poles
3. Illumination Calculation Using DIALux
With the official launch of the "Overall Plan for Football Reform," it is expected that primary and secondary schools across various regions will incorporate football into their physical education curriculum and increase the number of class hours dedicated to it. This indicates that the development of football fields will be a significant focus for our country in the future. Among these, fields designated for professional competitions and training are essential projects. The adequacy of lighting on these football fields is a crucial factor that determines whether regular competitions and training can take place. Thus, assessing the lighting design for football fields is a key aspect of the overall design process.
1. Football Field Lighting Standards
A specific outdoor football field measures 104 meters in length and 64 meters in width, classified as Grade III. It serves as a venue for professional competitions without television broadcasts. According to the "Sports Stadium Lighting Design and Testing Standards," the lighting requirements for outdoor football fields that do not have TV broadcasts are outlined in Table 1.
2. Proper Placement of Venue Light Poles
In accordance with 07D706-1 "Electrical Design and Installation of Sports Buildings," the lighting arrangement for football fields without TV broadcasts involves placing four light towers (poles) outside the four corner kick areas, ensuring they are out of the athletes' line of sight. The light poles should be positioned at a minimum angle of 5° on the outer edge and 15° on the lower edge, as illustrated in Figure 1. meaning they can only be placed within the designated oblique line area shown in the figure.
The height of the light pole is determined using the following equation:
h=d×tanα
Where: h—— The height of the light pole, m;
d——The distance from the kick-off point of the court (i.e. the center point of the court) to the light pole, m;
α — — The angle between the kick-off point of the court and the bottom and top of the light pole, φ≥25°.
In this project, the light poles are designated as T1. T2. T3. and T4. Since there is an athletic track surrounding the football field, the light poles need to be positioned at a specific distance from the track. The center of the field is represented by the coordinates Q (0.0) in meters, while the coordinates for light pole T1 are (-75.45). The distance from Q to T1 is:
d=√75²+45²
=87.5m
Light pole height:
h=d×tan α
=87.5×tan 25°
=40.8m
The light pole needs to be positioned 40.8 meters above the ground, while we have decided to set the center of the lamp at 42 meters. Based on the lamp post height and angle diagram shown in Figure 2. α represents the angle between the floodlight and the center of the field Q, ideally ranging from 25° to 30°. The distance from point J1 at the corner to point T1 on the court is s = 25.5 meters. Additionally, β is the angle between the floodlight and the nearest corner of the field, which should fall between 45° and 70°.
tanβ=h/s
=42/25.5
=1.647
β=58.7°
Tab.1 Lighting standard for outdoor football court
Fig.1 Location diagram for the lamp post
The previous calculations indicate that the location and height of the lamp posts fulfill the necessary requirements.
As shown in Figure 2. the four lamp posts are symmetrically positioned both vertically and horizontally at the center of the court, each located in their respective diagonal areas.
Fig.2 Height and included angle diagram for the lamp post
3. Illumination Calculation Using DIALux
Once the positions and heights of the football field light poles are established, the next step is to calculate the illumination. Before proceeding with the calculations, it is essential to choose a light source that aligns with the specified color temperature and color rendering index. For this project, we have selected 2000W lamps from a specific manufacturer, which have a color temperature exceeding 6000K and a color rendering index of 90. all of which comply with the specification requirements.
The lamps are to be installed at the four corners of the football field, with the projection lamps arranged in a matrix on the lamp poles. To simplify the calculations, the entire lamp post is treated as a single point. However, in real-world conditions, various factors can influence illumination, including nearby city lights, starlight and moonlight, atmospheric haze that absorbs and diminishes light, and reflections from the venue and surrounding objects. For the sake of simplification, these factors are disregarded in the design. During lamp installation, the angle and position of the lamps should be adjusted based on actual site measurements to ensure compliance with specification standards.
When using DIALux software for the calculations, we continuously perform trial calculations to meet the specification requirements. The grid size for calculating illumination on the outdoor rectangular sports field is set at 10m, in accordance with Article 8.2.2 of JGJ 153-2007. This project calculates the illumination at 221 points across the football field. Figures 3 to 5 display screenshots of the calculation results and the corresponding list.
Fig.3 Data graph for horizontal illumination
Fig.4 Data graph for equal-level illumination
The calculations indicate that 42-meter tall lamp poles are positioned at each corner of the football field, with each pole equipped with 25 sets of 2000W lamps. By adjusting the angle of projection, both horizontal and vertical illumination can be achieved on the field. However, since the football field is classified as Class III and is designated for professional competitions without a need for TV broadcasting, vertical illumination is not necessary. According to Figure 3. the horizontal illuminance on the field measures 778 lx, with a minimum of 554 lx and a maximum of 903 lx, resulting in an illuminance uniformity of U₁=0.61 and U₂=0.71. These values comply with the relevant standards.
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