Road Site Planning

A lack of supply in the current housing market is driving up prices and leading more folks to research and invest in new construction. With material costs still rising and interest rates likely increasing, this is not an easy decision yet, and further development is necessary to support today’s housing needs. For real estate developers with the capital to do so, building an empty piece of land is likely a money-making endeavor. Planning is essential before breaking ground on any new project, large or small, and this planning can be completed and visualized in Global Mapper with the help of Global Mapper Mobile and Geographic Calculator.

Roads are a primary necessity for a new development project as they create access to the land for the subsequent implementation of utilities and construction of buildings. The data collection options available in Global Mapper Mobile, along with the transformation expertise of Geographic Calculator and the visualization and analysis power of Global Mapper, make the Blue Marble suite of products ideally suited for road and construction planning.

Loading a Basemap

To begin a project in Global Mapper, one of the easiest ways to explore the study area is to import data from the program’s list of built-in free online sources. With sources for high-resolution imagery in the United States, and worldwide terrain data, the existing topography and cover of the proposed site can be loaded into a new workspace and used to quickly visualize the site of the new development.

Global Mapper’s Connect to Online Data tool makes it easy to begin exploring a location and creating a map.

In addition to utilizing Global Mapper’s built-in online sources, new sources can be added. In this example, parcel data from the state’s GIS library is added as an online source from an ESRI FeatureService layer. Streaming this data into the workspace helps to define the parcel owned by the real estate developer and the area available for development.

A feature service provided by the state can be added as a custom online source allowing polygon parcel data to be streamed into Global Mapper.

Point Cloud Analysis

Improving upon the lower resolution streamed data, lidar or point cloud data for the area can be loaded into Global Mapper or generated from drone-collected imagery with Global Mapper Pro’s Pixels to Points tool. For this area, the state data collection program has made data from a recent collection available. Once downloaded, the LAZ (LAS zip) file is loaded into Global Mapper Pro and can be displayed by elevation, classification, RGB (color) value, and many other characteristics.

The lidar draw modes in Global Mapper allow the attributes of the returns to be visualized in the top-down, Path Profile and 3D views.

Extracting an Existing Road

In order to plan the new road, the existing roads in the area need to be represented in Global Mapper to ensure a smooth connection with the new neighborhood. With the existing road being town-maintained, as opposed to state-maintained, no recent road line data is available. The existing road centerline will need to be derived from the loaded lidar data.

Global Mapper Pro’s Point Cloud Segmentation tool provides a customizable point cloud analysis allowing points representing unique features to be identified and labeled. With options to choose what attributes are considered in the analysis and how valued they are, unique features like the existing roadway can be identified.

Considering the point attributes available for analysis, normal and curvature values are included when aiming to detect the roadway since the road is relatively flat compared to surrounding wooded areas. Additionally, the return number is included, since the open roadway is represented primarily by first return points, and color is considered to help differentiate between the green vegetated points and the gray road representing points.

Using Global Mapper Pro’s Point Cloud segmentation tool, the open roadway is identified from the point cloud.

With segments of points representing the road identified, these segments are selected with the Select Lidar Segments tool, and a bounding area for the needed area of the road is generated for only the selected point returns. This roadway area provides a good boundary for the existing roadway, but the area needs to be cleaned up, and a centerline for the road needs to be generated.

Using the Global Mapper digitizer tools, skeleton lines are generated for the bounded road area. Skeleton lines are generated in segments for the area, and then joined into a single line and smoothed to remove any angular line joints. The modified skeleton line follows the road centerline and will be used as a reference for the new neighborhood road.

A road centerline is created by bounding the segments of lidar points representing the road, and then generating, combining, and smoothing skeleton lines for the area.

Generating Terrain

While the low-resolution terrain data streamed into Global Mapper provides a rough view of the development area, a higher-resolution terrain model can be generated from the point cloud loaded in Global Mapper Pro. The state-collected lidar data being used in this project has already been classified, so, in this case, Global Mapper Pro’s Automatic Ground Classification tool does not need to be used. The Grid Creation tool allows points to be filtered based on many characteristics, including classification. Using a binning method for grid creation, a high-resolution digital terrain model is generated. This high-resolution terrain model will be used to begin planning and visualizing the new roads.

A digital terrain model is generated using the binning minimum value method and by filtering the point cloud by classification in the Grid Creation tool.

To begin using this generated grid, per-vertex elevations are added to the 2D road centerline to create a 3D feature for the existing roadway. When planning in 3D space, in reference to the real world, lines and areas used in planning should be 3D as well.

Planning Roads and Collecting Data

The planned neighborhood roads can be loaded into the workspace or created in the workspace with Global Mapper’s manual digitizer tools. The created line features will be used as a guide for field data collection, where crew members with Global Mapper Mobile Pro and an external GNSS device will walk the proposed roads and collect 3D data.

Using the Mobile Data Management tool in Global Mapper, a Global Mapper Mobile Package file is generated to be wirelessly transferred to a nearby mobile device or saved and transferred via email or a shared drive. Once loaded into Global Mapper Mobile with the Pro edition licensed, the Advanced GPS tools are used to connect an external GPS device for higher accuracy data collection, and a GPS feature Create Mode is used to collect 3D lines representing the proposed roads.

Data in Global Mapper can be exported to Global Mapper Mobile Package (*.gmmp) format and shared to an iOS or Android device running Global Mapper Mobile.

Global Mapper Mobile makes it easy to take data from Global Mapper into the field and add to it with many GPS-enabled feature creation modes.

Vertical Transformation of the GPS-Collected Data

Before bringing the collected data back into the project workspace to analyze and model the new road paths, the vertical coordinate system of the data needs to be considered. The road path data collected in GPS-enabled Global Mapper Mobile records elevations or Z values in reference to WGS84 Ellipsoidal Height. The 3D point clouds and derived terrain model used in the project so far use the vertical system NAVD88. In order to convert the collected data’s vertical system, GeoCalc Mode in Global Mapper can be used.

Opening up a new workspace, GeoCalc Mode is enabled, allowing Global Mapper to access the geodetic datasource from the installed and licensed Geographic Calculator program in order to execute vertical and advanced horizontal coordinate transformations. With GeoCalc Mode enabled in a new workspace, a Global Mapper Mobile Package file with the newly collected data is loaded, and the new vertical system is selected on the Projection tab of Global Mapper’s Configuration settings. To complete the transformation, a geoid model vertical transform is selected, and the data is exported to a new file. In this case, the data is exported to Global Mapper Package format since it will be loaded into the main project workspace for further analysis.

In the Path Profile View, a GPS-collected road path is shown in reference to the terrain before and after the needed vertical transformation.

Visualizing and Measuring Proposed Roads

After loading in the transformed 3D line data collected in Global Mapper Mobile, the workspace now contains data representing the terrain, existing roadway, and new proposed roads. Focusing on the proposed neighborhood roads, the terrain creation and editing tools in Global Mapper can be used to model the altered terrain.

While the terrain in this area is generally flat, and the roads were planned to need minimal grading for construction, the GPS-collected per-vertex elevation values for the four proposed road paths can quickly be analyzed to determine the maximum slope along the line. Selecting the four lines and using the Digitizer Analysis/Measurement option to Calculate Elevation/Slope Statistics with the per-vertex elevations, new attributes summarizing the line slopes and elevations are added to each feature.

Attributes summarizing the slope and elevation change along the road paths are automatically generated from the lines’ per-vertex elevations.

From the calculated slope statistics, Road #1, connecting to the existing road network, has a maximum slope over the required slope threshold. Viewing the vertex information for this line, the slope of each segment is shown, and by consulting a Path Profile view, the high slope value appears to be along the shoulder of the existing road. Altering some of the planned roadway vertex elevations, the change in elevation can be distributed across a longer distance to reduce the maximum slope of the road.

As the per-vertex elevations are manually edited, the calculated slope of each line segment is updated.

To create a polygon representing the area the roads will occupy, buffer features are generated from the collected roadway lines. Using a buffer distance of a single lane for each side of each line and choosing to combine the overlapping buffers where roads connect, a single connected area is generated, modeling the road network area for the new neighborhood. The buffer is a 3D feature as it inherited the per-vertex elevations from the collected road line data used to create it.

From 3D road path lines, a buffer is generated representing the new road area.

Flattening the Roadway

Using the generated combined buffer area, a flattened terrain grid layer for the area is created using Global Mapper’s Generate Flattened Site Plan tool. With the option to use the feature’s per-vertex elevations, the new roadways are modeled in Global Mapper as a 3D terrain grid. The flattened roadway grid is a separate terrain layer in Global Mapper but can be displayed seamlessly with the larger area terrain model and combined with an export to any supported format.

The flattened roadway can be viewed in Global Mapper’s 3D Viewer, and a flythrough can be generated and recorded to share the visualization of the proposed road.

As a result of the flattened site plan creation, a volume calculation is completed to quantify the size of the project. The cut and fill volume to flatten the earth for the new roads is calculated based on the original terrain grid and the flattened site. This information can be copied and pasted into a report to go along with the project files generated in Global Mapper.

Creating a Flattened Site Plan from the 3D road area, a volume measurement is generated, quantifying the size of the earthworks project.

WORK MADE EASY WITH GLOBAL MAPPER

Beginning with available lidar data and using Blue Marble’s suite of programs, a comprehensive model for a network of roadways is created. With the use of Global Mapper Mobile data was collected in the field and combining Global Mapper with Geographic Calculator through GeoCalc Mode the data is sure to be both horizontally and vertically accurate to the selected systems.

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