A large airport in a mountainous area of China is planning construction for an additional runway to keep up with increasing traffic. Significant alteration of the surrounding mountainous terrain is required to make room for the runaway. The engineers in charge of this project are using Global Mapper to conduct a terrain analysis and investigate and compare potential runway positions against a digital elevation model (DEM) integrated from multiple sources of current and planned terrain data, to create a more accurate volume estimate of the terrain work to be done.

This part of the terrain planning process includes modeling flight patterns and required clearance zones against existing terrain. By comparing a DEM of the existing terrain to these hypothetical terrain designs, Global Mapper is used to calculate a more precise estimate of the amount of material to be excavated and how much additional fill will need to be purchased. The original estimate was over 100 million cubic meters; however, Global Mapper and other tools have helped the engineers optimize the location and terrain structure, reducing the filling and excavation estimate to less than 50 million cubic meters.

For this project, the mountain on the west side (upper left in the figure below) intersects the planned runway and the surrounding buffered surface. The initial estimate for removing this mountain required the excavation of up to 100 million cubic meters, which is a key and costly project challenge. By importing and superimposing CAD design schemes of the airport runway plans on top of a terrain layer in Global Mapper, engineers are able to analyze the terrain in the expansion site of each functional area of the airport, judge the filling and excavation conditions, and then find a more economical solution.

Creating Terrain Surfaces from 2D Data

Airport construction projects can often take more than ten years, from the planning stage to execution. During this time, changes in topographic maps from different sources can conflict due to inconsistent measurement times, different coordinate systems, and elevation systems. Many of the maps used in this project were contour lines formatted for use in CAD software. Global Mapper easily reprojected and gridded these discrete files into a single solid surface. To be used for predictions, this final elevation layer was made from a DEM, different kinds of 1:10000 topographic maps, and earthwork construction drawings. Volume estimates for the project are measured using this integrated terrain layer to represent the current terrain.

In addition to mapping the paved runway, the surrounding area needs a protection zone to help plan against ground obstacles during takeoff and landing. These protection zones are diagrammed in clearance charts. Different flight states have different charts, landing versus takeoff, and other maneuvers, all of which need to be satisfied in the final design. The clearance charts, or design schemes, are often designed as flat 2D CAD data that must be translated into a 3D surface for modeling. After using CAD to create a composite layer from different blueprints and clearance charts, Global Mapper was used to turn them into terrain layers for analysis (see below).

Comparing Terrain and Measuring Fill

The composite layer that was made from the gridded clearance charts, as shown in the image above, can be used to create a model of the finished terrain. The path profile tool identifies the lowest point of all specification layers by looking at the terrain from a perpendicular perspective. These lowest points can be used as control points to dictate the lowest points of elevation when excavating the mountain. Once the new elevation/terrain is known, excavation volume measurements can be calculated.

To estimate the volume of soil to be removed, the composite layer is intersected with the existing terrain layer. You can see in the image below that some terrain stands above and intersects with the composite layer, which interferes with the runway protection zones and needs to be removed. The smaller the area and height of the mountain intersect, the less earthwork volume, decreasing the cost of the airport. Multiple models can be created and compared in Global Mapper to find the best estimate.

In conjunction with CAD and other software, a comparison between the cut and fill plan related to the existing terrain is being modeled in Global Mapper. This workflow makes it easy to continuously adjust and optimize the planning scheme and earthwork engineering, compare different options, and find the best scheme for large-scale terrain planning of the airport.

Global Mapper’s terrain analysis tools are used to estimate the volume to be removed and create a 3D model of the new, cleared surface. It compares the lowest point from the composite layer against the existing terrain surface to measure the amount of soil needed to change the current terrain to fit the new surface.

Thanks to Global Mapper’s strength in vector and raster conversions, and accurate comparisons of DEMs, in conjunction with the optimization and adjustment of airport planning through multi-plan comparison and selection, the total reduction of filling and excavation volume has so far been reduced to 50 million cubic meters, and there is still room for further optimization.

WORK MADE EASY WITH GLOBAL MAPPER

This use case was submitted and translated into English by our Chinese reseller Ecarto. For more information about Global Mapper in Chinese, visit www.ecartotech.com.

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