February 1, 2022

Road Construction with Terrain Analysis in Global Mapper

Written by: Mackenzie Mills

 

The interlocking network of roads connecting us to our neighbors across towns, states, and countries, needs constant upkeep and expansion. Erosion monitoring and mitigation, resurfacing, and grading require some level of assessment and planning. Luckily, Global Mapper can help assess the current road situations, detect change over time, and even mockup plans for future improvements complete with 3D visualization and volume calculations. 

Data Collection with Global Mapper Mobile

Before any construction project can begin, a plan must be made, and that plan often involves a site visit capturing new data reflecting the current state of the site. Global Mapper Mobile allows for data prepared in Global Mapper to be taken into the field and augmented with new data points, lines, and polygons collected using GPS positioning. With options to set up Feature Template layers, in which the attribute structure is predefined to ensure consistent data collection, Global Mapper Mobile equips a field team to record a proposed or existing road path, place points at potholes, and capture images of the site that will be stored within the geospatial data.

By default, Global Mapper Mobile uses the internal location services of the mobile device, but with a Global Mapper Mobile Pro license, Advanced GPS options become available, including the option to use external GPS devices and RTK corrections. Collecting high-accuracy data at a job site location can better inform planning teams of the current state of the infrastructure and terrain.

New Road Planning in Global Mapper

Whether a proposed road path was collected in Global Mapper Mobile or digitized in Global Mapper, the line feature can be used as a starting point for modeling the road. Generating a Path Profile along the length of the proposed road path, the terrain along this line is visualized and with the Measure tool in the Profile View, the overall slope and slope along segments of the road can be measured. 

The yellow points shown in the Path Profile view are the vertices from the 3D proposed road line.

Cross-sectional profiles, showing a series of slopes across the proposed road area can also be shown using the Path Profile tool. Setting the Perpendicular Profile length to the proposed road width of 22 feet, the terrain structure across the road is displayed. In this case, the lengthwise slope of the road area terrain is acceptable, but the road area will need to be smoothed and flattened perpendicular to the centerline. 

To generate the ideal road area, additional vertices will first be added to the proposed road line before creating a buffer representing the width of the road. A Digitizer data creation option is used to generate point features evenly spaced along the line. Since the proposed road path is a 3D line feature with per vertex elevations, elevation values will automatically be generated for the points created along the line. The new set of 3D points are then connected into a single 3D line feature with many more vertices than the original proposed road feature. 

 

Creating a line with a higher vertex count creates a more detailed centerline for the proposed road.

With a 3D line accurately representing the center path for the road, a single buffer feature can be created to represent the entire road area. The elevations from the 3D centerline will be inherited by the buffer area, making it a 3D polygon. 

Shown in 3D, the area representing the new road intersects the existing terrain at various points.

With the elevation model and 3D road area displayed in Global Mapper’s 3D Viewer, the areas of the original terrain that lie above the proposed road surface elevation can be seen, indicating that a cut and fill procedure will need to be executed in order to construct this new road. 

The simplest way to generate a new surface representing the road and simultaneously calculate cut and fill volumes for this construction is with Global Mapper’s Calculate Flattened Site Plan tool. Using the option to derive the site plan from the per-vertex elevations of the road area, the tool generates a new terrain surface representing the flattened road. As well as creating a new gridded layer in the workspace, Global Mapper calculates the total cut and fill volumes required to create this ideal flattened surface. 

Using the arrow keys to view each of the sequential perpendicular profiles along the proposed road, the need for flattening is seen.

The new flattened surface is generated as its own layer in the Global Mapper workspace, and can be displayed and exported with the larger elevation model to create a single, seamless terrain surface. 

For additional information on using Global Mapper for road analysis and repair modeling, check out the Road Repair Analysis and Planning Industry Showcase.

If you would like to explore the data collection capabilities of Global Mapper Mobile, look for the app in the iOS App Store and Google Play Store! To explore terrain creation and analysis in Global Mapper, download a 14-day free trial today! If you have any questions, don’t hesitate to get in touch

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