## Materials and Methods
### Image Data Calibration and Processing  
We calibrated the raw AHS images using the Caligeo pre-processing tool (version 4.9.7, Specim OY, Oulu, Finland) to convert digital numbers (DN) to at-sensor radiance values. The radiometric calibration settings were derived from laboratory measurements by the instrument manufacturer in spring 2015. We used the atmospheric correction software ATCOR-4.7 (ReSe applications Schlapfer, Wil, Switzerland) to convert at-sensor radiances to TOC hemispherical-directional reflectance factors (HDRFs). The atmospheric condition was described with the maritime aerosol model (based on \begin{table}
\begin{tabular}{c c c c} \hline  & **I1** & **I2** & **I3** \\ \hline Time of acquisition (GMT+3) 03-07-2015 & 10:32 & 10:41 & 10:52 \\ Scatter angle (\(\beta\)) & 76\({}^{\circ}\) & 19\({}^{\circ}\) & 55\({}^{\circ}\) \\ Sensor heading (clockwise from N) & 291\({}^{\circ}\) & 141\({}^{\circ}\) & 293\({}^{\circ}\) \\ Solar angle (zenith, azimuth) & 48\({}^{\circ}\), 122\({}^{\circ}\) & 48\({}^{\circ}\), 125\({}^{\circ}\) & 47\({}^{\circ}\), 128\({}^{\circ}\) \\ Spatial sampling interval & 0.6 \(\times\) 0.7 m\({}^{2}\) & 0.6 \(\times\) 0.7 m\({}^{2}\) & 0.6 \(\times\) 0.6 m\({}^{2}\) \\ Sensor view angle & 28\({}^{\circ}\) & 29\({}^{\circ}\) & 8\({}^{\circ}\) \\ \hline \end{tabular}
\end{table} 
Table 1: Scene and data acquisition parameters. \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{1}{c}{**Sensor Parameter**} & \multicolumn{1}{c}{**Specification**} \\ \hline Spectrograph & High efficiency transmissive imaging \\ Spectral range & 400–970 nm \\ Number of spectral bands & 128 \\ Spectral bandwidth & 4.7 nm \\ Framerate & 60 Hz \\ Field of view (FOV) & 37.7\({}^{\circ}\) \\ Across-track pixels & 1024 \\ IMU & Oxford RT3000 \\ \hline \end{tabular}
\end{table} 
Table 2: Sensor specifications and configuration during acquisitions. Figure 1: Hyperspectral AISA Eagle II sensor and IMU system on a tilting platform looking in the nadir direction through the cargo bay entrance at the rear of the aircraft. The cables connecting the instruments have been removed for better visibility. We configured the sensor to scan with a 60 Hz framerate. The chosen configuration resulted in square pixels of approximately 60 cm for nadir view; in off-nadir directions, the pixels were slightly elongated (Table 1). Full technical characteristics of the sensor are given in Table 2.  
a seven-day air pressure trajectory coming from the Atlantic ocean). Aerosol optical thickness (AOT) was retrieved from the AERONET sun photometer measurement at the Hyytiala site for the time of image acquisition. The measured AOT value of 0.06 at 500 nm corresponds to a visibility value of 120 km in Atcor ([PERSON], pers. comm.). Water vapor column height was calculated from the 840 nm absorption feature, and pixel adjacency correction distance was set to 0.10 km. Georegistration and orthorectification were done with the Parge image rectification tool, version 3.1 ([PERSON], Wil, Switzerland). We used a digital elevation model with 2 m spatial resolution provided by Finnish National Land Survey. We selected 15 road intersections as ground control points from atmospherically corrected AHS images, and aerial photographs with 0.5 m spatial resolution (Finnish National Land Survey) to determine the boresight angles describing the alignment between the IMU axes and the optical axis of the sensor. For orthorectification of the atmospherically-corrected TOC reflectance images, we downloaded a 3D LiDAR point cloud dataset from the National land survey of Finland (2010, Paikkatietoikkuna) with a point density of 0.5 points per m\({}^{2}\). We used the LAStools package (version: 140615, Rapidlasso GmbH, Gilching, Germany) to separate ground and canopy returns. Canopy returns were filtered for outliers (more than 30 m above ground) and gridded to 10 m to create a digital surface model (DSM).