TITLE: Phenocamera RCC daily average composite image collection from Nybygget, southern Sweden.
SITES STATION: Asa Research Station
TIME PERIOD: 2019
TIME RESOLUTION: DAILY
TIME ZONE: UTC +1 
LATITUDE: 57.14975
LONGITUDE: 14.738164
ALTITUDE: 256.4 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 phenocamera RGB composites, from quality-filtered photos between 10 a.m. and 2 p.m.
The phenocamera is pointing to a coniferous forest composed by Norway spruce (Picea abies). The forest is part of the Asa High Yield Experimental Forest, which addresses questions regarding intensive forest management on a landscape level such as fertilization and water quality, intensive managed forest, introduces tree species and their influence on flora and fauna, intended to study the forest growth under different management regimes. The stand at Nybygget was planted in 2006 and it has been fertilized every second year since 2016. 

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 7.25 m above ground, looking south and a zenith angle of 90 degrees. The phenocamera operates all year long. It starts collecting photos at 5 a.m. and ends at 8 p.m. and takes one photo per hour.
The area surveyed by the phenocamera projects a footprint on the ground defined by the following coordinates(GCS WGS84, degrees decimal): 57.149056, 14.738542; 57.148935, 14.738187; 57.149169, 14.737859; 57.149468, 14.737882; 57.149650, 14.738173; 57.149353, 14.738487.

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. 
For phenology purposes, 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.





