TITLE: Phenocamera GCC daily average image composites collection from Skogaryd Central, western Sweden.
SITES STATION: Skogaryd Research Catchment
TIME PERIOD: 2018-04-27 10:00:00 - 2018-12-31 14:00:00
TIME RESOLUTION: DAILY
TIME ZONE: UTC +1 
SAMPLING POINT: Skogaryd Central, Mast 3 phenocam
LATITUDE: 58.363555
LONGITUDE: 12.149786
ALTITUDE: 76.2 m a.s.l.

FILE RETRIVED FROM: https://data.fieldsites.se Link to metadata landing page is available in separate file in the downloaded zip.
DATA POLICY: SITES data is licensed under a Creative Commons Attribution 4.0 international license (http://creativecommons.org/licenses/by/4.0/).

PARAMETERS & UNITS: Spectral Vegetation Index (fraction)

DESCRIPTION: 
Collection of phenocamera Green Chromatic Coordinate (GCC) index image composites averaged daily from quality-filtered images between 10 a.m. to 2 p.m.
The phenocamera pointed to an opening in the mature spruce forest with a few species of grasses and herbaceous plants, among others, wood horsetail (Equisetum sylvaticum), creeping bentgrass (Agrostis stolonifera) and common wood sorrel (Oxalis acetosella), on a floor of glittering wood moss (Hylocomium splendens) with some Polytrichum spp and red-stemmed feathermoss (Pleurozium schreberi).

SENSOR DESCRIPTION:
Data acquired with Mobotix M25 RGB phenology camera, with wide field of view (FOV) angle of 60 degrees. Images stored in JPG format.  

DATA ACQUISITION:
The original images were acquired with phenology camera on an observation mast, at a height of 3 m above ground, looking west (270 degrees) and an off-nadir angle of 42 degrees. The phenocamera acquired images from 4 a.m. to 8 p.m. every hour. The phenocamera operates all year long.  
The area surveyed by the phenocamera projects a footprint on the ground, the centroid of which is approximately defined by the following coordinate (latitude, longitude in GCS WGS84, decimal degrees): 58.363555, 12.149786.   

PROCESSING METHODS:
Low quality images were filtered out manually from the original image collection. Low quality refers to images that contain sun glare, rain droplets, fog, or shadows, or represent low-light or blurry conditions.
For phenology purposes, all images from 10 a.m. to 2 p.m. were averaged per band (RGB) and pixel, daily. GCC composites were calculated from RGB daily averages and exported as 8 bit grayscale images. Digital range of GCC image layers is 0 - 255 and should be scaled down using a factor of 1/255 to get pixel values in physical range.
GCC is defined as: DNgreen / (DNred + DNgreen + DNblue) (Richardson et al., 2009)

REFERENCES
Richardson, Andrew D., Koen Hufkens, Tom Milliman, Donald M. Aubrecht, Min Chen, Josh M. Gray, Miriam R. Johnston et al. "Tracking vegetation phenology across diverse North American biomes using PhenoCam imagery." Scientific data 5 (2018): 180028.

Richardson, Andrew D., Bobby H. Braswell, David Y. Hollinger, Julian P. Jenkins, and Scott V. Ollinger. "Near‐surface remote sensing of spatial and temporal variation in canopy phenology." Ecological Applications 19, no. 6 (2009): 1417-1428.







