TITLE: Phenocamera GCC daily average composite image collection from Laevasvagge, north-western Sweden.
SITES STATION: Tarfala Research Station
TIME PERIOD: 2019
TIME RESOLUTION: DAILY
TIME ZONE: UTC +1 
LATITUDE: 68.04203
LONGITUDE: 18.95922
ALTITUDE: 951.2
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 Red Chromatic Coordinate index (GCC) daily composite images, calculated from daily average RGB composite images, from quality-filtered photos between 10 a.m. and 2 p.m.
The phenocamera is pointing to a mosaic of Natural grassland (CORINE: 3.2.1) and Heathland (CORINE: 3.2.2) determined by the micro climate of a hummocky terrain in an arctic alpine valley.

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

DATA ACQUISITION
The original photos were acquired with a phenology camera on a observation tower, at a height of 4 m above ground, looking north-north-east (22.5 degrees) and a zenith angle of 80 degrees. The phenocamera operates from June to August. It starts collecting photos at 9 a.m. and ends at 3 p.m. and takes one photo every 30 min.
The area surveyed by the phenocamera projects a footprint on the ground defined by the following coordinates(GCS WGS84, degrees decimal): 68.041889, 18.959309; 68.049192, 18.999611; 68.053775, 18.990868; 68.057850, 18.971599; 68.057906, 18.955033.

PROCESSING METHODS:
Low quality photos were filtered from the original phenology photo collection using thresholds to the spectral signal of the photos (DN), as defined by Richardson et al., 2018. Low quality refers to photos that present sun glare, rain droplets, fog or shadows, or are night or blurry scenes. Low quality refers to photos that present sun glare, rain droplets, fog or shadows, or represent low-light or blurry conditions. 
For phenology purposes, all photos from 10 a.m. to 2 p.m. were averaged per band (RGB) and pixel, daily. RCC composites were calculated from RGB daily averages. 
RCC is defined as: DNred / (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.





