HALIS specializes in all aspects of aerial data acquisition; from flight planning and airspace coordination to collection of LiDAR, Imagery and Video, to post processing of calibrated data sets. Our planning, acquisition, and post processing methods allow us to consistently produce geospatial data products of the highest accuracy needed. HALIS has acquired LiDAR and Imagery for clients throughout the United States and Canada. Our unique system is capable of collecting data simultaneously from a helicopter or fixed wing platform.
We have partnered with several mapping qualified aircraft vendors throughout the United States. Having reliable vendors allows us to mount our sensors on various types of helicopters and fixed-wing aircraft. This enables us to respond quickly to our clients' needs while keeping mobilization costs as low as possible.
LiDAR (Light Detection and Ranging) has overtaken traditional photogrammetry as the technology of choice for the generation of elevation datasets on large projects or in areas where photogrammetry struggles, such as in leaf-on conditions or in areas of rugged terrain. In addition, the LiDAR sensor that HALIS owns and operates can generate more accurate datasets (better than 0.1' vertical accuracy), with faster timelines from collection to delivery.
Nearly all of our projects start with the acquisition of LIDAR, often including simultaneous acquisition of imagery. We have the ability to acquire from either a fixed-wing or helicopter platform, and routinely collect data from both within the course of week. Our system is designed to accommodate movement between platforms without requiring new calibrations as opposed to many of the systems in the market. Once acquired, the point cloud data is adjusted to surveyed control to ensure that the project can meet the accuracies required.
While no technology can truly 'see through the trees', LiDAR provides a much better chance of hitting the ground in heavily vegetated areas than other technologies. The likelihood of penetrating the canopy is increased with proper flight planning, to include increased point densities and opposing flight lines in some cases. With the techniques employed by HALIS, we have been able to accurately generate 1' contour datasets in heavily vegetated areas, even in summer months.
Seen as an industry-standard specification, we often use the USGS LIDAR Base Specification as a starting point for the planning of wide area mapping, especially if project timelines support leaf-off collection. Our management personnel have extended experience with the planning and completion of USGS Quality Level 2 (QL2) projects, including the acquisition, processing, hydro flattening, and final deliverables of wide area projects. For projects requiring more accuracy or definition than a typical wide area project, we have the leeway of flying a much denser point spacing from a lower altitude with a helicopter.
The system that HALIS employs for data acquisition includes two imagery systems, one for the generation of traditional orthophotography and another for the collection of oblique imagery and videos. The inclusion of imagery has always been an essential piece of most wide-area aerial surveys, and the ability to capture during a single flight makes it an economic addition on projects of almost any size.
The generation of orthophotography involves the removal of distortions inherent in aerial imagery from the effects of terrain and other factors. In order to remove the distortion, an elevation source is required. We utilize the LiDAR point cloud as the elevation source in the generation of orthoimagery, with an end product that is horizontally accurate at any point on the image. As a result, horizontal measurements can be made in the imagery between any locations in the project area.
Oblique imagery and video is especially important for the visualization of corridor features from a non-vertical view. On a transmission line project, for example, oblique imagery provides a view of the structures and towers along the route. Coupled with the vertical view from an orthophoto, oblique imagery provides a complete assessment of the project corridor from a standard office computer.
Imagery is delivered in common formats, such as TIFF or JPG. Coordinate information needed for insertion into a GIS or CADD software is included as either a 'sister' file known as a world file, or incorporated in to the image header in a format understood by geospatial softwares.
Until just a few short years ago, aerial mapping was completed by relying almost exclusively on imagery for data extraction. Now, the LiDAR densities that we collect can support heads-up feature extraction of most linear features (edge of pavement, structures, fences,...) and many point features (manholes, individual trees, poles,...), and we rely more and more on the LiDAR point clouds in our data extraction processes.
A normal data extraction project for HALIS begins with a LiDAR intensity image and an orthophoto generated from imagery flown during the same flight. Since the two datasets are flown at the same time, the positional data (AirBorne GPS and IMU) match exactly for each. The result is two very different types of datasets that match each other very closely, and each complements the other in the data extraction process. Horizontal positions of all features are compared to both the LiDAR intensity and orthophotography, and all vertical positions are extracted directly from the LiDAR point class.
The list of features to be extracted is determined through communication with the client, and is incorporated into the scope of work for the project. Through this communication, we can ensure that the features delivered meet the end needs of the project, without unnecessarily increasing the cost or schedule for final delivery.
Once all data has been extracted, we format the data for delivery according to the client's wishes. We routinely deliver in AutoCad or MicroStation formats, or in ESRI shapefile/geodatabase formats. Once extracted, the conversion process from one software to another is straight-forward, and we also often deliver in multiple formats for use by different disciplines on the same project.