Forest fires represent a constant threat to ecological systems, infrastructure and human lives. The only effective way to minimize damages caused by forest fires is their early detection and fast reaction, apart from preventive measures. Great efforts are therefore made to achieve early forest fire detection, which is traditionally based on human surveillance. There are two types of human surveillance - direct human observation by observers located on monitoring spots and distant human observation based on video surveillance systems. More advanced approach is automatic surveillance, automatic early wildfire detection and advanced distance video presence. In almost every country, which encounters high risk of forest fires, at least one such system was developed and proposed. Since 2006 Croatia also has its own, quite advanced and intelligent wildfire monitoring system (in Croatian called IPNAS). The system has been successfully implemented in various Croatian National and Nature Parks, but the most sophisticated installation is the Istra county wildfire-monitoring network.