Key issues in making and using satellite-based maps in ecology: A primer

The widespread availability of satellite imagery and image processing software has made it relatively easy for ecologists to use satellite imagery to address questions at the landscape and regional scales. However, as often happens with complex tools that are rendered easy to use by computer software, technology may be misused or used without an understanding of some of the limitations or caveats associated with a particular application. The results can be disappointment when maps are less accurate than expected or incorrect decisions when they are treated as truth. In this paper, we discuss several key issues which are critical to ensuring the effectiveness and value of remote sensing products, but which are also sometimes sources of confusion: (1) direct versus indirect models of land surface properties and processes, (2) differences between class-based and continuous mapping models, (3) scale, and (4) accuracy assessment. We illustrate our points with examples from the application of satellite imagery to forest management issues in the Pacific Northwest, USA. While our examples focus largely on Landsat image data, the issues we discuss have broad relevance across sensor data types, land cover properties, and geographic locations.