Last week, we explored the purpose and components of an LRS. This week, you’ll have an opportunity to solidify your understanding by completing some hands-on exercises to create routes, calibrate linear measures along a route, and use dynamic segmentation to convert event tables into event features. You’ll also see how GIS software can be used to reduce the burden associated with the creation and management of an LRS and event data.
Complete ESRI’s ArcMap tutorial [1] on linear referencing. Submit an M.S. Word document to Assignment 6-1 in Canvas which addresses the following questions:
In the next major release of ArcMap, LRS functions will be removed from the product. In the past few years, ESRI has been looking to shift users instead to their new Roads and Highways product which is designed to provide a fuller featured set of tools for transportation organizations to manage their LRS and roadway event data. A 57-minute introduction to this tool [2] was provided at the 2013 ESRI users’ conference.
Transportation organizations capture and maintain a large number of linearly referenced roadway events including:
Displaying more than a few of these on a single map can begin to clutter the map and make it difficult for the user to understand.
One tool which transportation organizations have used for many years to visualize road attribute information is a Straight Line Diagram (SLD). In an SLD, a roadway section of interest is presented as a straight line along with various roadway attributes or events. Often these roadway attributes are maintained by separate groups within the transportation organization, and sometimes they are linearly referenced using different LRMs. An SLD brings many attributes together with a uniform referencing method to facilitate visualization of the data and the potential identification of relationships between different data elements.
The specific layout of SLDs varies from one organization to another. One common layout for an SLD includes three components: a map component, a schematic component, and an attribute component. The map component often appears at the top of the SLD and presents the alignment of the route of interest. The schematic component, also sometimes referred to as a stick diagram, presents the route as a straight line and can incorporate roadway features such as intersections, bridges, ramp entrances and exits and legal boundaries. The attribute component includes roadway event data presented along the same horizontal axis. Linear events such as speed limit are displayed as a series of horizontal bars with the extent of each bar corresponding to the region over which the attribute has a constant value. Point events are displayed as point symbols positioned according to their location along the route.
Historically, SLDs were manually created and assembled into books for reference across the organization. Given the effort required to generate SLDs in this manner, the books often reflected data which was somewhat dated. Today, most SLDs are created dynamically from current event data using sophisticated GIS software applications.
As an example, the Massachusetts Department of Transportation uses a web-based tool called Massachusetts Route Log [3] to generate Straight Line Diagrams (SLDs). Here is an example SLD generated from this application for a portion of State Route 9.
Vermont’s Agency of Transportation (VTrans) has a similar SLD tool called VTrans Routelogs [4].
In this assignment, you will manually create an SLD for route 40001200 in Pitt County, North Carolina (the same county you worked with in Assignment 6-1). Submit the SLD as a M.S. Word document to Assignment 6-2 in Canvas. In your SLD, the positions of the events should be reasonable, but you can eyeball them. There is no need to be super accurate for the purposes of this assignment. The SLD should cover the portion of the route between milepost 8.5 and 11.5 and should include the following elements:
Route | Speed Limit | Beginning MP | Ending MP |
---|---|---|---|
40001200 | 25 | 0.0 | 3.0 |
40001200 | 55 | 3.0 | 9.0 |
40001200 | 35 | 9.0 | 10.0 |
40001200 | 55 | 10.0 | 15.0 |
Note: You can use whatever tools you’d like to create the diagram as long as it is submitted as an M.S. Word document. If you’d like, you can hand sketch the diagram. Assuming you don’t create the SLD directly in Word, you would insert an image or paste an image of your SLD into Word. My personal recommendation is to use a combination of M.S. PowerPoint with its drawing tools along with the Snipper utility in Windows.
Links
[1] http://desktop.arcgis.com/en/arcmap/10.4/manage-data/linear-referencing/an-overview-of-the-linear-referencing-tutorial.htm
[2] http://www.esri.com/videos/watch?videoid=2679&channelid=LegacyVideo&isLegacy=true&title=esri-roads-and-highways---an-introduction
[3] http://services.massdot.state.ma.us/mrla/RouteSelection.htm
[4] http://vtransmaps.vermont.gov/routelogs/map.htm