Sample Design Tools
Level 1 Users are users with little GIS and remote sensing experience or access to specialized GIS or remote sensing software or hardware. Level 1 users will mostly interact with Toolbox-generated products and web applications and may work with level-2 or level-3 users to use other Toolbox tools for their management information needs.
Level 2 Users have an understanding of GIS and rangeland monitoring data and have experience with GIS software. Level 2 users can do some minor data creation (e.g., creating layers to define new management scenarios) or edit existing layers (e.g., correcting and updating polygons in the vegetation maps). They will use Toolbox tools and products to aid analyses for their management questions and may also run new scenarios based on existing state and transition models and vegetation maps. These users may provide outputs to level 1 users but may also require assistance from level 3 users to set up datasets for some tools.
Level 3 Users have a highly-developed skill set for manipulating and analyzing GIS, remote sensing, and assessment/monitoring data. They will have access to specialized software and hardware for creating new data layers (e.g., creating image objects from new imagery) and would set up the data layers that level 1 and 2 users would have access to. These users could also lead the process of creating new state and transition models or vegetation maps for new areas. Use of Landscape Toolbox tools in major planning efforts (e.g. RMP) would rely heavily on level 3 users.WHAT ARE THEY?
One of the biggest challenges that rangeland researchers and managers face is how to gather the necessary data for decision-making as efficiently and accurately as possible. Often we know how we want to collect the data – meaning what method to use – based on objectives, but where to sample is an altogether different problem that has a large impact on not only efficiency, but in terms of how (or even if) the data can be generalized to other areas.
Most ecologists, managers, and private land owners are familiar with the idea that some degree of randomness in selecting sample locations is important. Simple-random and stratified-random selection are two important and commonly used techniques for picking sample locations. Using the Landscape Toolbox’s Multiscale Framework and Object-based Image Analysis (OBIA) tools, we can extend the capability of these familiar sample selection techniques to improve sampling precision and efficiency while not increasing the complexity of the sample selection process.
Of course, the Landscape Toolbox Sample Design tools built on OBIA can also support more complex sample-selection procedures like adjusting selection probabilities according to accessibility or project objectives in a manner that unbiased estimates can still be obtained.
HOW DO THEY WORK?
The basic idea behind using OBIA for sample selection is that an image segmented into polygons, or objects, at the right scale captures the pattern and distribution of vegetation community patches on the landscape. If we used the right scale in segmenting the image into objects, we may assume that the objects are homogeneous. This allows us to treat them as sampling units, and in order to measure that polygon, we need only to be able to navigate to it and stay away from the boundaries when sampling.
Another powerful aspect of using image objects for sampling comes when sampling is used to estimate rangeland condition for a large area. Because every place in a landscape is part of an image object whose area is known, we can determine the probability that any object is selected for sampling. This is important because if we know the selection probabilities, we can adjust them based on factors like study objectives or logistics (e.g., distance to roads) to make sampling more efficient. The altered selection probabilities are then used in calculating the estimate to “unbias” the result.
Stratification is another common approach that is used in selecting sampling locations in order to reduce variation between samples and divide a landscape into more homogeneous units. The best strata are based on characteristics of the landscape, and this is an area where coarse-scale image objects derived through OBIA can help greatly.
HOW DO I GET/USE THEM?
The Landscape Toolbox Sample Design Tools are intended for users with a moderate level of experience with GIS software and have been developed as an ArcGIS extension. In order to use the Sample Design Tools, a set of image objects created from OBIA is necessary. Image objects can be created for any area using OBIA software and used with the sample design tools. But because access to OBIA software is currently very limited, we have created sets of image objects for portions of southern Idaho that can be downloaded from the Landscape Toolbox Data Center and used in the Sample Design Tools.