Accurate Highway Mapping

PROJECT PLANNING

Flight Plans.  All existing mapping and coordinate lists will be used in the preparation of the flight plans for data acquisition. Planning will be completed with the POSTrack GPS guidance system with flight lines superimposed over Google Maps of the area. Flights will be planned so the helicopter flies at an elevation that will result in the accuracy required by the project. Most of our flight are flown at approximately 800 to 1000 feet AGL above the terrain of the project. Our mapping system collects LiDAR and color imagery during the same flight and they are both geo-referenced using Airborne GPS and IMU data. The allows us to create a color ortho of the project and use the DEM from the LiDAR as the base for the ortho. If aircraft are required for the project, we will use either our Leica RC-30 camera or the Applanix DSS Digital Color Camera to collect imagery for mapping. Pilot guidance computers ensure that the pilot precisely knows the helicopter position at all times and maintains the flight plan.

Ground Control. Two GPS base stations are operated so that the trajectory can be computed if one of the stations malfunctions. The ground control points will be surveyed by the use of GPS and normal practice is to place survey caps to reflect the point number and client identification. The points will be surveyed from existing HARN (NGS) stations if they exist in the area. If adequate HARN stations are not in the vicinity, the points are occupied for at least two hours for producing an OPUS solution for the points. All surveying will be completed in Grid NAD 83 coordinate system and NGVD 88 vertical datum.

Daily Mission Planning. Data acquisition missions are planned for durations of approximately two hours for the helicopters and four hours for the aircraft. Satellite availability and GDOP is determined in advance of each day’s missions to ensure satisfactory satellite coverage and geometry for accurate data acquisition. Each day’s mission is scheduled to avoid any predicted periods with inadequate satellite coverage.

 

PROJECT EXECUTION

Ground Mobilization. Following client approval of flight plans; the mission crew mobilizes to the project location. A Tuck ground survey crew (or other agreed upon survey crew) will locate and prepare ground control points for the aerial survey. These points will be plotted on the flight plan map.

Helicopter Mobilization and Initialization. The helicopter will be mobilized to the closest airport or to the project area if landing is permitted. The eagleeye mapping system will be initialized for approximately five minutes before the flight and for at least five minutes after the helicopter engine is shutdown. This will allow the helicopter trajectory to be calculated in both forward and reverse directions and the two trajectories to be merged for maximum reliability and accuracy.

Data Collection Flights. Each data collection flight will be flown at 800 to 1000 feet AGL to achieve the desired result for the client. The altitude can be established and maintained based upon the project mapping needs. The altitude is maintained by the nadir reading of the LiDAR displayed on the pilot display.

Safety. Safety is always a top priority for all Tuck Mapping projects. All employees are well trained and fully prepared for their job assignments. Flight operations are performed in full compliance with FAA regulations and helicopters are well maintained in accordance with all FAA regulations.

Adequate speed is constantly maintained so that safe autorotation can be accomplished if an engine problem occurs during data acquisition. We do not fly lower than 300 feet AGL to provide sufficient altitude for the pilot to take proper action during an emergency. This safe altitude and safe airspeed allow time and distance to safely land the helicopter in the event of an emergency.

DATA PROCESSING

Mission Data Quality Control. Data acquired during a mission is always checked before the helicopter leaves the project area to ensure that quality satellite data was obtained and that all systems on the helicopter and on the ground performed properly. If any problems are discovered, the mission is immediately flown again.

Field computers are used to process trajectory data and to check LiDAR coverage before relocating for the next mission. Basic geo-referencing of the LiDAR data and the digital images is completed as soon as the mission ends. The GPS and IMU of the eagleeye system provide simultaneous direct geo-referencing of the LiDAR point cloud and the digital imagery. The GPS guidance system compares the actual line locations with the planned flight lines.

After the data has been checked for quality and coverage, a back-up copy is prepared. Depending on the duration of the mission and the urgency of the project, the data is either transmitted immediately or safely maintained until return to the office for point cloud and digital imagery processing. Data is processed using TerraScan software for the classification of the point cloud and to separate the point clouds into the applicable feature levels.

 

DELIVERABLES

Tuck Mapping consults with each client about potential projects to thoroughly understand the clients intended usage of the mapping data. This is done in order to ensure that the results delivered by Tuck meet the clients’ needs. The eagleeye mapping system can provide a wide range of imagery and LiDAR data to meet client needs including:

Imagery – High-resolution digital photography with pixel resolution of 4-6 inches is available depending on the helicopter’s altitude. The appropriate altitude is selected based upon the clients intended usage of the photography. Photography is geo-referenced and orthorectified for preparation of a continuous map of the route.

Still imagery of any structures is also available as needed. Tuck Mapping Solutions uses a Nikon D-200 (10.3 megapixel) digital camera with GPS referencing to provide imagery of all the structures.

If video is required of the line, we will use our FLIR ULTRA MEDIA II 36X RGB camera system. The system has a 5-Axis Gyrostabilized Mount that is joy stick controlled by the camera operator. It has a pan range of 360° and a tilt range of +20° to -105°. The camera has a zoom extent of 36X. The data is recorded to a Red Hen data recorder that provides GPS metadata so the projection of the camera can be displayed and also the data can be inserted into ArcInfo products.

LiDAR Data. The system obtains laser point density of 20-30 data points per square meter with an absolute vertical accuracy of approximately 1 to 2 inches. Data is provided to create a Digital Terrain Model at the specified width. This data is provided in the agreed format normally with a description, coordinates (X, Y, Z), feature code and any comments.

Format. Planimetric drawings can be provided in the client specified format to show all major topographical features pertinent to the project.