﻿TITLE: Phenocamera RCC daily average composite image collection from Röbäcksdalen, north-eastern Sweden.
SITES STATION: Röbäcksdalen Field Research Station
TIME PERIOD: 2019-04-11 2019-10-23
TIME RESOLUTION: DAILY
TIME ZONE: UTC +1 
LATITUDE: 63.806340
LONGITUDE: 20.232638
ALTITUDE: 6.5 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 (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 traditional 5-year crop rotation of one year of barley, another year of barley and undersown ley (a mix of Phleum pratense, Festuca pratensis, Trifolium pratense), and 3 more years of ley. Occasional years other crops, such as wheat, oats, peas, can be cultivated as well.
2019 was in the first year of ley, originally seeded on May 29, 2018 as a mixture of timothy (Phluem pratense cv. Tryggve) and red clover (Trifolium pratense cv. Yngve). 

SENSOR DESCRIPTION:
Data acquired with [Phenocam brand and model] RGB phenology camera, with a field of view angle (FOV) of [FOV in degrees] degrees. Photos are stored in JPG format.  

DATA ACQUISITION
The original photos were acquired with phenology cameras on a observation tower, at a height of 10 m above ground, looking west (265 degrees from north) and a zenith angle of 67 degrees. The phenocamera operates between April and November. 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): 63.804035, 20.225015; 63.805520, 20.223187; 63.806803, 20.223436; 63.808142, 20.229417; 63.806327, 20.233030.

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 represent low-light or blurry conditions. 
All photos from 10 am to 2 pm 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.





