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LIDAR has revolutionized the acquisition of digital elevation data for large scale mapping applications. Merrick has embraced this technology from the onset through associations with several LIDAR acquisition vendors. Since 1997, we have successfully used LIDAR data as input to the contouring and digital ortho processes. We operate our own proprietary digital imaging/LIDAR system and processes. A typical LIDAR system rapidly transmits pulses of light that reflect off the terrain and other height objects. The return pulse is converted from photons to electrical impulses and collected by a high-speed data recorder. Since the formula for the speed of light is well known, time intervals from transmission to collection are easily derived. Time intervals are then converted to distance based on positional information obtained from ground/aircraft GPS receivers and the on-board Inertial Measurement Unit (IMU) that constantly records the attitude (pitch, roll, and heading) of the aircraft. LIDAR systems collect positional (x,y) and elevation (z) data at pre-defined intervals. The resulting LIDAR data is a very dense network of elevation postings. The accuracy of LIDAR data is a function of flying height, laser beam diameter (system dependent), the quality of the GPS/IMU data, and post-processing procedures. Accuracies of ±15cm (horizontally) and ±15cm (vertically) can be achieved. Accuracies better than 7cm (vertically) were achieved because of initial testing of Merrick?s system. Customized ScopeMerrick accomplishes LIDAR missions with the most advanced LIDAR sensor on the market today and can provide highly accurate elevation postings as the primary source for DTMs. Using Merrick's state-of-the-art LIDAR sensor, we are able to collect higher density datasets with a single pass flight. This LIDAR data is filtered to accomplish the accuracy requirements of the proposed contours and ortho datasets. Before flight and data acquisition, all airborne GPS reference base stations identified for use in controlling the project are submitted to the client for review and approval. Typically, a single base station is required to cover a 25-mile flight radius. The base station points selected are typically High Accuracy Reference Network (HARN) or other bluebooked National Geodetic Survey (NGS) control points. Base stations are established on these points before any airborne data collection. GPS position data will be recorded at one-second intervals, or epochs, throughout the entire mission. Merrick Total Turnkey Solutions
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| Automatic Building Extraction |
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| Natural Color Digital Imagery Draped over LIDAR |
Integration
Tools
Support Services/Consulting
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| Infrared Digital Imagery |
DACSTM is manufactured by Merrick & Company and consists of a Kodak Charge Coupled device (CCD) with a 4080 x 4080 pixel array @ 14 bit-per-pixel dynamic range color and IR imagery. The system collects clear imagery at better than 6-inch (15cm) resolution at >120-mph ground speed (altitude dependent).
The color digital camera subsystem consists of a large-format camera, which simultaneously collects imagery with better than 6-inch image resolution matching the swath width of the scanning laser. Three separate removable storage acquisition systems log data to hard drives and flash card media for immediate access to data and subsequent automated processing of data products. These include: Flight Management System, POS Controller, Data Laser Logger, and Camera subsystems. The system is integrated in a twin-engine aircraft appropriate for flying projects at 100-150 knots. A flight management system facilitates automated exposure of image photo centers, with real-time monitoring of the mission flight path via pilot display.
The system is compatible with a variety of lens combinations. Shutter speeds of up to 1/4000 are achieved with the focal plane shutter allowing for elimination of forward motion compensation (FMC). High-speed data transfer is achieved, utilizing fiber optic interfaces and proprietary loss less compression to achieve transfer rates of 48 MB @ <2.5 seconds per frame allowing for <0.5 ft pixel resolution. Stereo coverage at >120 knot ground speed.
The system receives command from an automated programmable flight management system to fire the camera at specified geographic locations at a rate of 2.5 seconds or greater. Three image formats are written during each sequential frame: BMP, JPG, and binary compressed. The latter is used to produce post-processed, full resolution 48 MB TIFFs. Real-time imagery and histogram information are displayed simultaneously at full resolution for in-flight radiometric balance, shutter speed, and exposure monitoring/adjustments.
Large-scale ortho mosaics & stereo compilation for 3D planimetric feature collection are achievable with DACSTM Imagery.
Digital Camera
Data Logger
Software
Imagery
Other
Complete Documented Workflow Training Includes:
Integrated with Photogrammetric Applications:
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