Goniometer Pool
Contact Persons
Dr. Daniel Schläpfer |
Keywords
Bidirectional Effects, Goniometry, Dual-view FIGOS, LAGOS, Spectral Radiometry, BRDF, Laboratory
Abstract
The Goniometerpool operates one measurement equipment, the Goniometer, which can be used either in an indoor (LAGOS) or outdoor (dual-view FIGOS) configuration. For both configurations the same spectroradiometer is used. For laboratory goniometer measurements an irradiance source is necessary in order to simulate the sun light. The dual-view field goniometer system FIGOS is operated with two spectroradiometers (of the same type) which simultaneously collect the reflected and incident radiation at high spectral and angular resolution. It is the first operational hyperspectral goniometer system and allows for an accurate field BRF retrieval of selected targets following an approach proposed by Martonchik et al. (1994). The Goniometer equipement consists of:
- The Goniometer construction
- One (LAGOS) or two (dual-view FIGOS) spectroradiometers (ASD FieldSpec-3) mounted on the Goniometer
- An Irradiance Source (for LAGOS)
- A power supply with an intensity control unit (for LAGOS)
- Laptops for storing the spectrodirectional data (wireless connection to the spectroradiometers)
Instruments
LAGOS*/Dual-view FIGOS*
Parameter | Description |
Manufacturer | Lehner & CO. AG, Graenichen (AG) Switzerland |
Spectral Range | 350-2500nm |
Channels | continuous |
Linear Arrays | (1) 512 Si, 350-1000nm |
Bandwidth | 1.4 nm (350 - 1050nm) |
Scan Time | 100 ms |
Field of View | Dependent on fore-optic |
Size, Weight (without sensor) | Diameter: 4 m / Height: 2m, about 230 kg |
Power / Power supply | Regular AC-generator for field usage / 24 V |
Digitization | 16 Bit |
Wavelength Accuracy/Repeatability | ± 1 nm /± 0.1 nm |
Spectrum Averaging | Yes |
Dark Current Correction | Automatic |
Operating Environment | 10 - 90 % Humidity, -10° to 50° C |
Possible zenith view angles (t) | - 75° < zn < 75°: |
Angular precision | ± 0.5° |
Time to set up | ± 2 h |
Time to measure one hemisphere | 20 min (with a resolution for az = 30° and zn = 15°) |
Irradiance Source (LAGOS) | |
Observation hemisphere | LAGOS: Ground hemisphere (reflected radiation) |
* can be operated using the GER 3700 or the ASD FieldSpec. For dual-view field measurements only the ASD FieldSpec-3 spectroradiometers can be used.
Purpose:
The LAGOS (Labor-Goniometer System) and dual-view FIGOS (Field-Goniometer System) is actually the same instrument. It is designed for experimental studies of the Bidirectional Reflectance Factor (BRF) either in the laboratory or in the field. The LAGOS has been installed in a dark room labor at the University of Zurich. For measurements with the LAGOS an artificial Irradiance Source is needed. For measurements in the field, the goniometer system can easily be taken apart and transported to any place by a vehicle. In the field, it is operated with two spectroradiometers. The dual-view FIGOS is the first operational goniometer systems which is capable of simultaneously measuring the reflected and the incident radiation at high spectral and angular resolution. Thus, such a dual-view goniometer datasets provides the potential to perform an accurate BRF retrieval of selected targets.
