Earthwork Construction Planning with Global Mapper
Engineers and surveyors use Global Mapper to pre-plan earthwork projects to maintain uniformity, high stability, and long-term performance through the lifecycle of a given venture.
Transportation government agencies worldwide use Global Mapper for roadway excavations and embankments. Planning and construction are also other areas of increasing use for the software.
Maintaining the integrity of current transportation networks and building new infrastructure is fundamental to keeping roadways working smoothly and safely. Global Mapper helps engineers visualize projects before they are implemented, increasing stakeholder engagement, community understanding, and practical incorporation. The application’s powerful analysis tools help users save time, money, and effort by providing a way to begin planning without using limited resources on field visits and surveys.
Global Mapper’s Terrain Painting tool provides engineers with the means to visualize projects during the early planning stages for infrastructure elements such as ramps for highways, ditches for stormwater runoff, and more. The Terrain Painting tool offers several operations and brush types for sculpting or manipulating the terrain allowing engineers to simulate each phase of the site preparation and construction process.
The Terrain Painting tool dynamically edits the elevation values of gridded elevation datasets, including DSMs, DTMs, bathymetric datasets, lidar-derived terrain data, and more. When using the Terrain Painting tool, the software modifies the pixel values of the elevation layer instead of superimposing a secondary surface model on the terrain, which is the case when using Global Mapper’s Calculate Flatten Site Plan tool. Several operations are available to edit the terrain, including Fill Gaps, Smooth Terrain, Set Terrain Height, Raise Terrain Height, Lower Terrain Height, Slope Terrain Along Line, Slope Terrain Across Line, Set as “No Data,” and Revert to Original Heights. The Point, Line, and Area brush types of a user-defined size are available to select the area of interest to edit. Terrain Painting is the most convenient and uncomplicated way to create early designs in Global Mapper because the tool works like a paintbrush with easy ways to undo and redo work if mistakes are made.
TYPES OF VISUALIZATION
Planners can choose to visualize their data differently depending on their target audience. The 2D view is where the elevation data can be “painted” to display the changes implemented. Showing the changes in terrain data in the 2D view is great for projects that have a drastic change, such as a ramp or other plans that impact the elevation shader. In the 2D view, hill shade can be enabled, adding a light source to the 3D data to add shadows and enhance the visualization of texture on the terrain surface.
A cross-section of the elevation changes along a vertical profile is rendered with the Path Profile tool. Changes in elevation across ditches, embankments, berms, and ramparts are easily identified using this tool.
Edits to the terrain appear more evident in the 3D Viewer, whether they are significant or not. Enabling the Eye Dome Lighting effect provides advanced lighting techniques to highlight the elevation data in 3D, making features in the terrain more apparent. Also available in the 3D Viewer is the option to generate a 3D Fly-through, which can be exported to standard formats like an MP4 for easy access. The 3D Fly-through option gives Global Mapper the ability to record the event centering around a specific option or flying a path, which could help simulate driving with transportation projects.
Medians are typically a portion of roadway between two opposing lanes of traffic that separate them, increasing motor vehicle and pedestrian safety. Three different types of medians exist: raised, flush, and depressed, all with different criteria and benefits. In the example below, we create a raised road median using the Set Terrain Height operation in the Terrain Painting tool. The Set Terrain Height option edits the area of interest to project a certain height and levels the elevation.
With these Terrain Painting Options, used to create a raised median, this operation will set the terrain within the drawn area to a height of 3.8 meters.
In this case, both lanes of the road are at an elevation of approximately 3.3 meters; the goal is to create a raised median at an elevation of 0.5 meters higher than the roadway. We set the height for the terrain at 3.8 meters and use the Area (vertex) mode brush to trace the region where the median is planned.
This option is also helpful in flattening a site where workers will stage equipment for construction.
A Path Profile, cross-section view across the median shows how the terrain painting operation set the median to a single height.
2D views of before and after painting the median.
With the flattening of the median, the rough area between the roadways has been modified to a single elevation value.
A few different ramps can be designed for transportation, including on and off-ramps for entering and exiting highways and runaway truck ramps that allow for vehicles experiencing difficulties. The Slope Terrain Along Line operation in Global Mapper changes the elevation to match the specified slope along the drawn line. The slope is applied using degrees, percent, or ratio slope, depending on the data specifications. The line’s starting height is derived from the first vertex and will slope upwards if positive and downwards if negative. In the following example, we draw a line from the road to the bridge at a 7.5-degree angle to simulate an off-ramp built from the middle of the bridge. We also use the Smooth operation at the top of the ramp to help the transition of the existing structure and our created one.
The Terrain Painting options used to create a ramp slope the terrain at 7.5 degrees along the drawn line.
The sloped terrain created with the Terrain Painting tool shows the planned ramp allowing traffic from the bridge to exit onto local roads.
3D views of before and after painting the ramp.
BERMS AND RAMPARTS
Highway and roadside berms and ramparts are raised barriers that act as dividers between a road and another area, such as a body of water or a residential area. Berms are typically constructed of compacted earth, rock, or gravel. In the example below, we used the Slope Terrain Across Line function. This operation changes the elevation to match the specified slope perpendicular to the drawn line. The slope is drawn from the middle of the line to the left, right, or both sides as determined by settings. The line will slope upwards, generating a wall with a positive value or downwards, creating a ditch with a negative value. In this case, we draw a line alongside the outside of a road to simulate a berm that would prevent stormwater runoff from the paved surface from advancing into the water below. We use an exaggerated slope degree to visualize the barrier on the map efficiently.
To create the berm, terrain will be painted to slope to slope 30 degrees on the left of the drawn line. The other side of the upslope area, the edited terrain will be feathered back to the existing grid values.
A cross section view perpendicular to the painted terrain shows the enhanced berm above the steep drop in elevation.
From an 2D overview the painted berm appears smoothed and slightly taller.
Looking down the berm from either side, it is clear the berm has been raised in height and smoothed by the new slope painted onto the existing terrain.
Roadside ditches help to prevent erosion of the roadway and water seepage into the road subgrade. There are many different shapes of ditches, such as circular, rectangular, and trapezoidal, and types of cover like vegetated and concrete, all with unique construction and maintenance requirements.
Depending on the ditch’s specifications, this workflow can be performed with either the Slope Terrain Across Line operation with a negative slope value or the Lower Terrain Height operation. In this example, use the Lower Terrain Height option to decrease the terrain’s height in the specified area incrementally. We draw a line along the roadway to simulate a water runoff drainage ditch. Please note that we use an exaggerated elevation to help visualize the capabilities of the brush.
To create a ditch in the terrain the heights are lowered by 10 feet along a line. The lowered terrain is then feathered into the surrounding terrain.
A profile view across the ditch shows the lowered terrain. The sloped bottom of the ditch is derived from the slope of the original terrain.
From above the footprint of the new wider ditch is seen stretching from the bottom toward the top of the view.
From an oblique view looking down the length of the created ditch, the lowered terrain and feathering into the unaltered terrain is clear.
Global Mapper can calculate the approximate material volume the project requires. When using the Terrain Painting tool, it is best to use the Measure Volume Between Surfaces option to calculate the edits to the elevation layer. This command compares two terrain layers in the workspace. After loading an additional unedited version of the terrain into the workspace, the Measure Volume Between Surfaces function accurately calculates the amount of material added to or taken away from the project site. In the example below, we select the unedited layer to subtract from the edited layer to calculate the raised median. The Cut Volume is the amount of material that we need to build the structure.
The Measure Volume Between surfaces setup compares the edited terrain layer to a loaded version of the original, terrain. The results of this volume calculation show the volume of terrain cut away and the volume or terrain added, or filled, by the above terrain painting operations.
WORK MADE EASY
WITH GLOBAL MAPPER
Swasey, B. (2021, April). By The Numbers: Biden’s $2 Trillion Infrastructure Plan. NPR.org. https://www.npr.org/2021/04/01/983470782/by-the-numbers-bidens-2-trillion-infrastructure-plan
The American Road & Transportation Builders Association. (2017). Highways Policy. https://www.artba.org/government-affairs/policy-statements/highways-policy/
TRIP. (2020, April). Key facts about the US surface transportation system. https://tripnet.org/wp-content/uploads/2020/04/TRIP_Fact_Sheet_NATL.pdf