## 8 Discussion  
Our review revealed that the various phases of environmental policy require up-to-date and synoptic spatial information, at various spatial scales, on the state of the environment and the extent and magnitude of environmental and policy impacts over larger areas. Earth observation is ideally suited for this, as a large number of variables relevant to environmental policy, but by far not all, can be detected remotely. Moreover, remote sensing permits repeated and consistent assessment and monitoring of the environment; it allows independent control and its quality can be assessed. As such, it is a tool with some very desirable characteristics for supporting environmental policy. Why, given this potential, is remote sensing not used more widely? It has been stated frequently that remote sensing may address user requirements more cost effectively than traditional environmental information acquisition methods. Having the potential to be more cost effective, however, does not automatically lead to utilization of remote sensing. It makes a difference whether the technology is introduced in an existing or a new market; cost of market development might prohibit the opening of new markets, while competition with vested interest might frustrate the introduction of remote sensing in markets served by more traditional data capture methods. In these cases, one might consider [67] suggestions to compare the costs and value of the information provided by remote sensing to other techniques. Apart from cost effectiveness, one also has to consider characteristics which determine the user's appreciation of the value of the information, such as its accuracy, reliability, consistency, and timeliness of delivery. Increasing standards for accuracy, reliability, and consistency are important fields of remote sensing research, as they increase the competitiveness of remote sensing products relative to traditional earth and atmosphere based measurements. The importance of timeliness of delivery in post hazard assessment has been stressed in drought [68], flood, and other hazard impact assessments [69]. Timeliness of information delivery is also crucial in radar detection of illegal fishing boats, as well as illegal oil spills, to allow the navy to intercept suspect vessels [45]. The examples given in this review confirm the picture that environmental policy creates a demand for remote sensing. This has implications for the possibility of financing remote sensing applications, as the opportunities for funding differ throughout the policy cycle. The best opportunities to acquire financial support are within the _policy implementation_ phase, because of the significant budgets typically available for policy implementation. Likewise, it should be possible to mobilize budgets for _policy control_ from within operational interventions, as good governance requires a more proactive attitude towards policy enforcement and control of fraud. Most examples of the use of EO for _policy evaluation_, rather than being intentionally integrated into the implementation of running policy, appear to have been developed by interested researchers. Remote sensing, with the caveats given, has great potential to evaluate policy, but budgets for policy evaluation are typically more difficult to acquire as this evaluation tends to be \"forgotten\" when implementing policy. Evaluation is considered an integral part of any policy cycle, and it is here that the effectiveness of governance could be assessed. Financing from within existing policies is not straightforward for the _problem identification_ function of EO, as it precedes the implementation of policy and the release of the related budgets. Considering the use of EO in a policy context made us realize how policy dependent EO is. There is a potential for policy independent environmental EO applications, for example, in precision agriculture [70] and insurances [71-73].