Axis Communications Q2901-E Thermal network cameras Performance consideration - Page 7

Heavy rain 11 dB/km 17.6 dB/mile Weather conditions and attenuation Light rain 4 dB/km 6.4 dB/mile Urban pollution 0.5 dB/km 0.8 dB/mile Dense fog 80 dB/km 128 dB/mile Fog 10 dB/km 16 dB/mile For example, an AXIS Q1921/-e Thermal Network Camera with a 60 mm lens as used in the earlier example (Figure 4.) will have a range of 300 m (328 yd.) with 6 pixels on target a clear day. A foggy day the attenuation will be 10 dB/km or 1 dB/100 m, resulting in an attenuation of 3 dB in total. The 3 dB attenuation means that only 50 % of the emitted energy from the object will reach the thermal sensor, degrading camera performance and the reliability of integrated Intelligent Video applications. Therefore, installations where one single camera is working close to its maximum performance should be avoided. A better option is to use several cameras to cover the given distance. This will safe-guard reliable operation by meeting the required amount of pixels on target and also reassure that the emitted energy from the object is sufficient. 6. Conclusion Being the market leader, Axis has the largest partnership program and can offer the widest range of third-party intelligent video applications. This document presents different factors to consider when integrating Axis thermal network cameras with intelligent video applications. Using Johnson's criteria as a starting point to determine the required number of pixels at a certain range is crucial and the corresponding software requirements should always be investigated. Weather conditions constitute another factor that will affect the performance of the installation. Even though the number of pixels meets the requirements, the temperature difference between the background and the object might not be enough to reassure reliable application operation. For example, the attenuation should be taken into consideration if a thermal network camera is to be installed where dense fog is frequent. For maximum performance, always test the camera and the intelligent application in the actual environment where it is to be used and to avoid performance and reliability problems. 7. Useful links For more information, see the following links: >> Axis Communications - 'Axis thermal network cameras - High-quality detection in dark and challenging conditions': www.axis.com/files/brochure/bc_thermal_40618_en_1009_lo.pdf >> Axis Communications - 'Some like it hot - Thermal cameras in surveillance': www.axis.com/files/whitepaper/wp_axis_thermal_cameras_en_37661_0912_lo.pdf >> Axis Communications - 'Axis thermal network cameras - Reliable detection, 24 hours a day, seven days a week': www.axis.com/products/video/camera/thermal/technology.htm 7