Airborne Laser Terrain Mapper Optech ALTM Gemini
Engineering specifications:
| Operation altitudes | 150 – 4000 m above surface | ||
| Basic specification of accuracy | Frequency of laser radiation | Horizontal accuracy | Vertical accuracy |
| 33 kHz 50 kHz | 1/5500 x altitude | From < 5 cm to 500 m From < 10 cm to 1 km From < 15 cm to 2 km From < 20 cm to 3 km From < 25 cm to 4 km | |
| 70 kHz | 1/5500 x altitude | From < 5 cm to 500 m From < 10 cm to 1 km From < 15 cm to 2 km | |
| 100 kHz | 1/5500 x altitude | From < 10 cm to 500 m From < 15 cm to 1 km From < 20 cm to 2 km | |
| 125 kHz | 1/5500 x altitude | From < 10 cm to 500 m From < 15 cm to 1 km | |
| 143 kHz | 1/5500 x altitude | From < 15 cm to 500 m From < 20 cm to 1,000 m | |
| 167 kHz | 1/5500 x altitude | From < 15 cm to 500 m From < 35 cm to 750 m | |
| Number of recorded reflections of laser pulse | At most 4 distance measurements for every pulse including the last reflection. | ||
| Intensity recording | The dynamic range of 12 bits for every measurementі | ||
| Scanning frequency | Measured; maximum, 70 Hz | ||
| Scanning angle | Measured; from 0 to ± 25° with step of ±1° | ||
| Compensation of rolls | Refresh rate of 5 Hz (scanning angle + angle of compensated roll = 30°, for example, ± 20° means that compensation amounts to ± 10°) | ||
| Bandwidth of aerial imagery | Adjusted; from 0 to 0.93 x altitude (m) | ||
| Geo-positioning system | The POS AV™ 510 (OEM) system includes the in-built 72-channel GNSS–receiver (GPS and GLONASS) | ||
| Laser radiation frequency (in the mode of tracking of several targets) | 33 kHz (maximum, 4.0 km AGL) 50 kHz (maximum, 3.0 km AGL) 70 kHz (maximum, 2.5 km AGL) 100 kHz (maximum, 2.0 km AGL) 125 kHz (maximum, 1.6 km AGL) 142 kHz (maximum, 1.4 km AGL) 167 kHz (maximum, 1.2 km AGL) | ||
| Hard disk for data storing | Durable replaceable hard disk (7 hours of uninterrupted recording when laser frequency amounts to 100 kHz) | ||
| Divergence of laser ray | Double divergence - 0.25 millirad (1/e) and 0.8 millirad (1/e) | ||
| Laser class | Class IV (FDA CFR 21) | ||
| Power-supply voltage | 28 V (direct current), 35 A (maximal current value) | ||
| Operation temperature | Control block: from 10° to +35° C Laser sensor: from -10° to 35° C (thermal stabilization using is assumed) | ||
| Storage temperature | Control block: from – 10° to + 50° C Control block: from – 10° to + 50° C | ||
| Humidity | 0 – 95 % without condensate | ||
| Dimensions and weight of control block | 653 mm x 591 mm x 485 mm, 55 kg | ||
| Dimensions and weight of laser sensor | 298 mm x 249 mm x 437 mm, 23 kg | ||
Advantages of ALTM GEMINI:
- the multi-pulse technology is applied. It provides frequency of probe pulses in the amount of 157 kHz at most;
- high scanning frequency (70 hz at most);
- the intellectual control system of laser scanning operation automatically regulates frequency of laser probing pulses, thereby the problem of ranging ambiguity is solved;
- receiving high density 3-d data of high accuracy;
- opportunity to use device at night;
- realization of independent channels for measuring coordinates and intensity in absolute coordinates with reciprocal accuracy of measurements between pulses in the amount of 5 cm at least;
- performance of aerial imagery of the area object, when conducting aerial-imagery operations for manufacturing of large-scaled cartographic products (1:5,000 and larger), amounts to 1,000 square meters per less than 12 flight hours and is provided with opportunity to output the digital terrain model within 24 hours after aerial imagery finishing;
- ranging to object independently on type of its surface.
Airborne Laser Scanners of the ALTM class are used for:
- large-scale topographic mapping in scales of 1:500, 1:1,000, 1:2,000 and smaller;
- building of digital relief models (drm), digital terrain models (dtm), and 3-d digital models;
- solution of wide spectrum of applied problems including those ones in the field of oil and gas industry, land management and cadastre creation, engineering surveys, inspection of power lines and other line objects (oil- and gas pipelines, motor-roads, railways etc.), in the field of forestry, ecology, prevention and monitoring of emergency situations etc.