Bellingham Trail Networks: Linear Referencing for Safety and Recreation, Study Guides, Projects, Research of Geography

Download Bellingham Trail Networks: Linear Referencing for Safety and Recreation and more Study Guides, Projects, Research Geography in PDF only on Docsity! Linear Referencing Trail Networks in Bellingham, WA and Surrounding Areas Peter Omdal and P. James Cortese Geography 452 – Spring 2005 Background The use of trail networks is a popular source of enjoyment and leisure for people who are passionate about outdoor recreation. Optimal enjoyment requires knowledge of the area and proper safety procedures in the case of an accident. Having quality data about a trail network readily available is the first step toward gaining knowledge about terrain and taking the appropriate safety measures that accompany this sport. Bellingham, WA and the surrounding areas contain a variety of recreational trail systems of varying length and difficulty. Although information about all these trails is available in one way or another, it is not quick and easy to use or locate. GIS is a perfect tool not only to portray trail data through maps, but to assist in prompt rescue missions in the case of an accident. Because all the public trails in the region are managed by different organizations such as Larabee State Park, the city of Bellingham, and Whatcom county parks, there is no single map or data source that displays every trail at once. Previously the data for these trail networks existed on our server at Western Washington University in a scattered, unorganized format. Little to none of it was in a geodatabase or even in the same folder and location. If this trail data was organized and linear referenced, hikers and dispatchers would have a new tool so one calculate distances from one point to another based on both ground distance and the time it takes to hike each trail. Objectives The purpose of this project has four components: 1) organize the existing data in a geodatabase, 2) update and validate the existing datasets, 3) generate new GPS line segments for trails not yet mapped, and 4) linear reference trail segments so that public safety dispatchers can easily and quickly locate incidents, as well as provide difficulty levels to the general public (Municipality of Anchorage, Alaska). Methods: Correcting the Data Over the years many people have contributed to the data used for the larger Bellingham Trail Network project. Because of this, much of the data is disorganized, and some of it is outdated. The first task was organizing the data into a geodatabase, with each trail system getting its own associated feature dataset. Within each feature dataset there are feature classes, one contains all of the trail data for that particular system, and then there are several other feature classes, depending on the amount of linear referencing routes that will be created. The second task was to verify the trail data. This involved using air photos to make sure the trail data was actually on a trail, as well as going out into the field and using GPS. For example, in Boulevard park there is a new boardwalk which is part of the interurban trail, but was not in the data set (see below). The third task was to prepare the data for linear referencing. Linear referencing requires that the lines in the feature classes share vertices when they cross the pre-existing line that you want to add the route to. Once your route is traced, you can add measures inside the sketch properties box. The measures can then be symbolized using the hatching options within the route feature class properties (see below). For the trails project, we are using linear referencing to add measures of distance to commonly used trails within each trail system. Also, using books and local knowledge of the trail systems, we can assign a difficulty rating to each loop. This will be extremely helpful for people who are considering hiking or mountain- biking a certain loop, and want to know how long the loop is, and how difficult that loop is. Results Using the topology editor and air photos the trail data has been fixed. For example, there were places where the lines just didn’t connect, or there was some random dangle (see below). Before After In other cases, there were overshoots and undershoots which were fixed. Undershoot: Before After Overshoot: Before After The results of the linear referencing can be seen on the maps on this website. Conclusions Prior to linear referencing, the trail data needed to be edited for accuracy. Due to tree cover, steep mountains, and the number of available satellites, the GPS data for the trails were not always accurate. The easiest technique for correcting errors of this type is through air photo interpretation. By starting an editing session in ArcMap, the line data could simply be moved directly over the top of the actual trail in the air photo. This form of editing has caused some data sets to be more useful and accurate than others. For example, the highest resolution air photo References Municipality of Anchorage, Alaska http: //www.ci.anchorage.ak.us/mayor/mapping.cfm