Centerlines of Roads

Centerlines

Centerlines are vector line on the roads that represent the geographic center of the rights-of-way transportation network. Road centerlines for an existing road can be developed through the GPS data collection and digitization of road on aerial photographs techniques (Extension, 2008).

Maps and GPS

The norm for a long time has been that maps are generated and updated by photogrammetric methods applied on the pictures taken by airplane and, of late on satellites image with the advancement in the satellite technology. The results were established to be good, but a manual adjustment was necessitated on areas that were hard to map for example areas that treetop blocked visibility of the road. Maps were also not updated regularly hence contained inconsistencies about the actual road hence the use of GPS. The GPS by storing the sequence of the georeferenced point collected by the receiver, a trace is created that represents the trajectory of the moving object that is created (Henrique & Baldo, 2013). A combination of the trace from the one or more vehicle is then used to build a centerline map of the path they traveled. This will form the base of the road map for the centerline.

Analyzing GPS Data

One of the main challenges of the GPS is how will the data collected be analyzed which is significant in identifying road centerline. The problem was attributed to the fact that civilian GPS receiver is not entirely accurate in their inference from the trace form of a cloud of a point along the road, and the only remaining way is to find the centerline through trial approximation. Regarding such a challenge the suitable technique could be an evolutive algorithm that can be used to approximate a good solution after many iterations.

Obtaining Georeferenced Data

Another question of importance especially when thinking of generating map is how to obtain the georeferenced data, and one possible solution is to use Smartphone. This is due to its sensor, including a GPS receiver, all of which are important in obtaining a range of information about how, when and where the user is moving. The device is carried close to the user hence further complicate the matter as it bring the additional problem of identifying the transport vehicle used along each trace.

Alignment and Cost Considerations

The minimum alignment required for the center line while considering its influence on the haul cost, construction cost, and environmental cost hence the preferred method will be horizontal alignment as opposed to vertical alignment. This is especially due to the constraints imposed by the terrain. Adjustments in horizontal alignment may help in reducing the potential for generating roadway sediments. The objective of manipulating the horizontal alignment is to strive to minimize roadway cut and fill as well as avoid the unstable area. When unstable or steep slopes must be traversed, adjustment in vertical alignment can minimize impact to produce a table road by reducing cut and fills. On level grounds however adequate drainage must be provided to prevents pending and reduces upgrade saturation.

Preliminary Survey Methods

Achieving the required objectives need a more thoughtful preliminary survey to be completed than would be done for a more conventionally designed road. The two method mainly used are one the grade or contour location method (mainly used when grade is controlling), or the centerline location method (used when the grade are light and alignment is controlling).

Reference

Extension. (2008, July 11). What is a road centerline? Retrieved February 25, 2018, from Extension: http://articles.extension.org/pages/37952/what-is-a-road-centerline

Henrique, G., & Baldo, F. (2013, November 23). A method to automatically identify road centerlines from. Retrieved February 25, 2018, from Geoinform: http://www.geoinfo.info/proceedings_geoinfo2013.split/paper8.pdf