Geodetic and Photogrammetric Infrastructure
The precise, high quality aerial imaging provided by Airborne Sensing is combined with the latest advances in geodesy and photogrammetry in all our project designs to ensure that our completed projects meet or exceed client specifications. With over 20 years of experience in airborne GNSS post-processing, we boast complete project planning infrastructure, an in-house professional surveyor, direct georeferencing through our GNSS/IMU Position Orientation System (POS), automated aerial triangulation processes with manual oversight, geodetic ground survey capacities, and creation of Digital Surface Models (DSMs) and orthophotos. In addition, we have scanning equipment available to bring analog film products into digital image processing and photogrammetrical environments.
Precise Positioning Experience
Over 20 years ago, Airborne Sensing developed an interface that sends the mid-point of an exposure signal to the GNSS event-marker log. The system notes exactly when the camera shutter was open at its mid-point and allows for the precise (less than 300 mu// µ) location of the perspective centre at the instant of exposure. Eccentricity parameters between the antenna phase centre and the optical nodal point are known to within 1 mm x,y,z. The system logs all in-flight GNSS data for further post-processing.
Complete Project Planning Infrastructure
Airborne Sensing has established procedures for project planning to ensure that all delivered materials are consistent with client specifications, and our surveys are designed according to the use of active networks in the area and static GNSS observations.
Using Geographic Information Systems (GIS), we make maps of flight lines, project areas, airport bases, and existing geodetic controls.
From these maps, we consult with control and spatial referencing agencies (at the municipal, provincial and federal levels) to determine levels of accuracy available, and how these relate to the project specifications and we determine what active GNSS networks exist in the area (e.g. CORS, CACS, other Virtual Reference System (VRS) networks). Then we compute transformations of these networks.
The GIS-produced maps also form the basis of our photo control. Using the common points established by the geodetic control, we can design our photo projects to align with GIS overlays. In consultation with the client, we design the project with suitable targets and photo identifiable types.
The geodetic and photogrammetric products are processed with the following programs:
Applanix: Direct georeferencing Inpho: Aerial Triangulation observations BINGO: Aerial Triangulation Grafnav: Kinematic GNSS processing from airborne sensor with no IMU input Grafnet: Static GNSS network adjustments from GNSS base stations PPP: Precise Point Positioning to compute GNSS base station coordinates TRNX: Federal transformation software to transform reference frames from year to year NTV2: National datum conversion software Global Mapper/AutoCAD/Google Earth: GIS to develop map overlays
In-House Professional surveyor
Our geomatics manager, Robin Poot, has over 20 years experience as a professional surveyor for engineering, geodetic and photogrammetric surveys of projects small and large, through North America, Latin America and the Caribbean. Trained in Germany, Canada and the U.S., Robin is a registered Geodetic Surveyor with the Association of Ontario Land Surveyors (AOLS).
Direct Geo-Referencing and Aerial Triangulation
The GNSS/IMU Position and Orientation System (POS) used by Airborne Sensing was developed by the Applanix Corporation. The GNSS/IMU POS collects GNSS positioning data during flight at 1Hz or 2Hz, and IMU data at 200Hz. It measures the position of the camera relative to the centre of the earth to less than 15 cm, as well as the angle of the camera relative to the mathematical surface of the earth to slightly more than 1/1,000 of a degree. Output from this device is then post-processed using GNSS/IMU post-processing and filtering algorithms to compute the x,y,z and w,p,k coordinates of the camera at the time of exposure.
The outputs from the GNSS/IMU POS can be used for direct georeferencing of image data. This direct georeferencing provides moderate accuracy with a very rapid turnaround. This data can also be put into a further transformation process for full aerial triangulation.
Our aerial triangulation system is almost completely automated, enabling rapid processing of data through Applanix, Inpho and BINGO software. There are multiple points of manual oversight within the system to ensure accuracy according to client specifications.
Results are immediately useable in a user’s analytical photogrammetric system for vector mapping, image mapping or other types of mapping.
Base Station Geodetic Surveys
Airborne Sensing has 4 Novatel DL Millennium base stations with geodetic antennae, tripods, power supplies and data-logging computers. Combining base station data with values obtained from a ground reference station recording simultaneously, we can determine the perspective centres of these stations to accuracies within less than 10 cm in x,y and 15 cm in z. Airborne Sensing helped pioneer the use of this technology in airborne photogrammetry.
These base stations provide the most widely deployable ground data collection unit available; this versatile structure allows us to conduct operations with high accuracy in areas where existing geodetic survey where existing geodetic survey networks are sparse, unreliable, or otherwise inaccessible or unusable. Airborne Sensing conducts the majority of its operations in Canada, where many regions have sparse geodetic networks; this system has been highly beneficial for operations in other regions, such as Santo Domingo and Jamaica.
Digital Surface Model (DSM) and Orthophoto production
We can quickly extract digital surface models through image matching, at a fraction of the cost of traditional photogrammetry or LIDAR. These models, especially when made of sparsely vegetated areas, are suitable for: orthophoto production, engineering models, volume computation, and initial engineering design.
Airborne Sensing also produces orthophotos for clients, generating seamless, radiometrically-balanced mosaic images. These are developed from the house-produced DSM or other existing models, such as LIDAR surveys, or provincial or municipal data sets.
As a provider of traditional (analog) aerial film products, Airborne Sensing recognizes the need for these images to be manipulated within digital infrastructures for DSM and orthophoto production. Through Airborne Scans, we offer advanced solutions for scanning film into a digital environment, using the following pieces of equipment:
– Vexcel 4000HT Photogrammetric Scanner to convert film images into raster files for softcopy photogrammetry and digital image processing. (Better than 1 micron geometric accuracy – equivalent to 1 cm on the ground in 1:10,000 scale photography.) – Vexcel ULTRASCAN 5000 for additional capacity as well as 10 bit grayscale.