﻿TITLE: Phenocamera RCC daily average composite image collection from Abisko Observatory, north-western Sweden.
SITES STATION: Abisko Scientific Research Station
TIME PERIOD: 2015-04-01 2015-11-30
TIME RESOLUTION: DAILY
TIME ZONE: UTC +1 
LATITUDE: 68.353729
LONGITUDE: 18.816522
ALTITUDE: 392 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 Red Chromatic Coordinate index (RCC) daily composite images, calculated from daily average RGB composites, from quality-filtered photos between 10 a.m. and 2 p.m. 
The phenocamera is pointing to Mount Nuolja. The ecosystems in the photos are subalpine birch forest (Betula pubescens var. czerepan) and alpine shrubland (mainly Salix spp., Empetrum nigrum, and Vaccinium vitis–idaea) in the upper slope of Mount Nuolja.

SENSOR DESCRIPTION:
Data acquired with Nikon D300s RGB phenology camera, with a lens of 35 mm focal length. Photos are stored in JPG format. 

DATA ACQUISITION
The original photos were acquired with phenology mounted on the rooftop of the observation house, at a height of 4.5 m above ground, looking to west and a zenith angle of 90 degrees. The phenocamera operates between April and November. It starts collecting photos at 10 a.m. and ends at 2 p.m. and takes one photo every two hours.
The area surveyed by the phenocamera projects a footprint on the ground defined by the following coordinates (GCS WGS84, degrees decimal): 68.353723,  18.816493; 68.347368, 18.717158; 68.354645, 18.712982; 68.361581, 18.719109; 68.365734, 18.732465. 

PROCESSING METHODS:
Low quality photos were filtered out 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 represent low-light or blurry conditions. 
All photos from 10 a.m. to 2 p.m. were averaged per band (RGB) and pixel, daily. RCC composite was 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.





