DOI: 10.23729/a6e8e2ef-0b72-411c-b011-ceae2d956f3a
title: Koli Kelluu Airship Spring 2023

description: The dataset comprises a remote sensing dataset captured in Koli National Park in North Karelia (63°5'29.916"N, 29°48'36.012"E). The major purpose was to follow the tree mortality caused by the European spruce bark beetle (Ips typographus L.) outbreak that poses a significant threat to Norway spruce (Picea abies H. Karst) dominated forests.

Data capture was conducted by Kelluu Ltd. using their hydrogen-powered airship technology. The airship was equipped with a MicaSense RedEdge-P MS camera (AGEagle Aerial Systems Inc., Wichita, Kansas, USA) and a Basler Ace2 RGB camera (Basler AG, Ahrensburg, Germany), both installed on a gimbal Gremsy T3V3 (Gremsy JSC, Ho Chi Minh City, Vietnam). Global Navigation Satellite System (GNSS) antennas were installed on the top of the airship to enable code-based GNSS localisation of image centres. Additionally, a downwelling light sensor (DLS2) for the MS-camera was installed on top of the aircraft for sun angle and sun irradiance measurement.

The MicaSense RedEdge-P dataset has been stored in multiple subfolders under the folder "MicaSense". The total size of the dataset is 577 Gbyte. The RedEdge-P camera comprises five MS bands and one panchromatic band (Band specifications: central wavelength, full width at half maximum, FWHM):
- Blue (475 nm; 32 nm), 
- Green (560 nm; 27 nm), 
- Red (668 nm; 14 nm), 
- Red-edge (717 nm; 12 nm)
- Near-infrared (842 nm; 57 nm)
- Panchromatic (643.5 nm; 463 nm)

Each band is stored in a separate file in the format imagenumber_bandnumber.tif, with the band number corresponding to the band number listed above. The MS cameras had a 5.5 mm focal length and a sensor with dimensions of 1456 × 1088 pixels, while the panchromatic camera had a 10.3 mm focal length and a sensor size of 2464 × 2056 pixels. 

Image metadata stored in each file has all relevant information to enable processing of the data
- GNSS coordinates of image centers (WGS84 coordinate system, orthometric height)
- Downwelling light sensor (DLS) data
- Exposure and gain settings 
- Interior orientation parameters: focal length and image principal point
- Black level offset
- Vignetting Polynomial 2D
- Bands offset
- User is referred to the manufacturer website (https://support.micasense.com/hc/en-us) for more information.

The Basler Ace 2 RGB dataset has been stored in two sub-folders under the folder named "RGB". The total size of the dataset is 34 GByte. The Basler Ace 2 camera had a focal length of 25 mm and sensor with 5320 × 4600 pixels. All essential information is provided in the metadata of each image file.
- GNSS coordinates of image centers (WGS84 coordinate system, orthometric height)
- Exposure settings 
- Interior orientation parameters: focal length
- User is referred to the manufacturer website (https://www.baslerweb.com/en) for more information.

The flights were conducted at an altitude of 100–120 m above ground level resulting in a ground sample distance (GSD) of approximately 1.2 cm for the RGB data and 7 cm and 3–4 cm for the native and pansharpened MS data, respectively. The full area was covered with approximately 80 flight lines.

The dataset was captured under sunny weather conditions. There was still some snow in the area, and deciduous trees were leafless. 

Additionally, six ground control points (GCPs) were measured using Topcon Hiper HR RTK GNSS receiver (Topcon Corporation, Tokyo, Japan) by Finnish Geospatial Research Institute. The GCPs were targeted with circular targets. They cover approximately 60% of the eastern part of the area. The coordinate system is WGS84 and N2000 orthometric heights. GCPs are stored in folder "Ground Control Points".