The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008 
Figure 1: Hierarchical structure holding dual-view goniometer 
data plus sunphotometer measurements for one target 
2.3 Data Storage 
Data is stored in the spectral database SPECCHIO (Hiini & 
Kneubiihler, 2007). It is a central repository for spectral data 
and associated metadata, based on a MySQL relational database. 
The database is interfaced with a Java application, providing 
graphical user interfaces for data input, editing, visualising, 
processing and output. The long-term usability and shareability 
of the spectral data is supported by metadata, consisting of 34 
variables, effectively defining the so-called metadata space 
(Hiini et al., 2007b). 
2.4 Metadata Generation 
Among the host of metadata variables that are required to be 
entered into the database, the following subset is of major 
importance for the retrieval process and is thus elaborated in 
greater detail: spatial sampling position, capturing time, 
illumination and viewing angles. 
3.1 Dataflow and Processes 
The pre-processing includes a number of calculations that are 
detailed in the following subsections. Figure 3 shows the 
dataflow diagram (DFD) of the dual-view FIGOS data pre 
processing. Input sources are the spectral database SPECCHIO 
and, optionally, MODTRAN lookup tables (LUT). 
3.1.1 ASD - MFR Intercalibration 
The intercalibration is required to make measurements of the 
involved instruments comparable. 
The intercalibration procedure yields intercalibration factors for 
each MFR band, thus enabling the correction of MFR data with 
the ASD instrument being taken as the reference. 
Calculation of the factors is based on the total irradiance E tot , 
directly measured by the MFR and indirectly by the ASD. 
E to t_ASD can be calculated from Spectralon (Labsphere) 
reference panel readings: 
E 
tot _ ASD 
(«»)= 
R„(0°A) 
(Eg. 2) 
The SPECCHIO application offers functions for the automated 
generation of metadata such as the calculation of the 
sampling/illumination geometry. 
The goniometer angles can be calculated based on the temporal 
sequence of the spectroradiometer files, as the movement of the 
goniometer is predefined. Figure 2 shows the sampling points 
projected onto a 2d Cartesian coordinate system. Sensor zenith 
angles range from 0° - 75° at 15° intervals and azimuth angles 
from 0° - 330° with a step size of 30°. 
Where 
L r u, R (0°,# 0 ) = Spectralon reflected radiance, measured from 
nadir for the given illumination zenith angle. 
R WH (O°,0 o ) = Correction factor for the non-lambertian 
behaviour of the Spectralon panel, obtained 
from the BRF of the panel for the given zenith 
angles (Sandmeier et al., 1998; Schopfer, 
2008). 
Goniometer Sampling points 
• ♦ • • ^ 
-0.5 - : : * - 
• • : 
t 
? * «! 
-1.0 1 I I I I j I I I ! j ! I I I I I I I > I 
-1.0 -0.5 0.0 0.5 1.0 
Figure 2: FIGOS sampling point positions 
The sun angles can be calculated if the sampling time in UTC 
and the spatial position in latitude and longitude are given. A 
UTC timeshift utility enables to correct local time to UTC while 
the spatial position can be entered manually or directly read 
from the ASD binary files if a GPS device had been connected 
to the system during the sampling process. 
3. PRE-PROCESSING 
The goal of the pre-processing is to produce the input quantities 
required for the subsequent BRF retrieval. This input data must 
be contained within one single spectral space, i.e. the number of 
bands, the central wavelengths and spectral response functions 
must be the same for all spectral data vectors. 
Eioi asd is then convolved to the narrow MFR bands and 
intercalibration factors are calculated for each channel of the 
E, 0 , mfr ■ These factors are subsequently applied to the E dirMFR 
data. 
3.1.2 ASD Intercalibration 
Intercalibration between the two used ASD instruments is not 
relying on data captured during the goniometer sampling 
experiment but based on factors obtained during a laboratory 
calibration campaign (Schopfer, 2008). The according 
intercalibration factors are stored as vectors in the SPECCHIO 
database and can be retrieved by an SQL query with constraints 
on the involved instrument numbers and the sampling date. 
The reference instrument is the downward looking ASD as it is 
used to capture the Spectralon reflectances that are utilised for 
the MFR intercalibration. Thus, both MFR and upward looking 
ASD are tied to the same reference instrument. 
3.1.3 E dir Generation 
The MFR instrument measures with a temporal frequency that 
allows the determination of E dir for every sampling position of 
the goniometer. However, the limited spectral resolution and 
range of the MFR data is not sufficient for the BRF retrieval 
that requires E dir to be available with the same number of bands 
and spectral resolution and range as the incoming and upwelling 
radiance measurements. 
To achieve the transformation of E dir MFRJC into the spectral 
space defined by the ASD sensor, E dlrMFRic must be augmented 
by E dir ASD . E dirASD is calculated by applying the ratio between 
Edir mfr and E tot MFR to E tot A sD■