ABoVE: Study Domain and Standard Reference Grids

The Arctic - Boreal Vulnerability Experiment (ABoVE) has developed two standardized spatial data products to expedite coordination of research activities and to facilitate data interoperability. First, the ABoVE Study Domain encompasses the Arctic and boreal regions of Alaska, USA, and the western provinces of Canada, North America. Core and Extended study regions have been designated within this Domain and are provided in both a vector representation (Shapefile) and a raster representation (GeoTIFF at 1,000-meter pixel resolution). Second, a Standard Reference Grid System has been developed to cover the entire Study Domain and also extends to the eastern portion of North America. This Reference Grid is provided as a nested pair of polygon grids at scales of 240- and 30-meter spatial resolution. A shapefile is provided for each grid. Note that the designated standard projection for the all ABoVE products is the Canadian Albers Equal Area projection.

Three data files are distributed with this data set: (1) a compressed shapefile (.zip) contains a vector representation of the Core and Extended study regions; (2) a GeoTIFF (.tif) file that is a raster representation of the Core and Extended study regions at 1,000-meter pixel resolution; and (3) a compressed (.zip) file containing shapefiles for the 240- and 30-meter spatial resolution nested Standard Reference Grids.

Project: Arctic-Boreal Vulnerability Experiment (ABoVE)

ABoVE is a NASA Terrestrial Ecology Program field campaign that will take place in Alaska and western Canada between 2016 and 2021. Climate change in the Arctic and Boreal region is unfolding faster than anywhere else on Earth, resulting in reduced Arctic sea ice, thawing of permafrost soils, decomposition of long-frozen organic matter, widespread changes to lakes, rivers, coastlines, and alterations of ecosystem structure and function. ABoVE seeks a better understanding of the vulnerability and resilience of ecosystems and society to this changing environment.

The Arctic - Boreal Vulnerability Experiment (ABoVE) has developed two standardized spatial data products to expedite coordination of research activities and to facilitate data interoperability for the creation of new data products for distribution across the ABoVE research campaign.

First, the ABoVE Study Domain encompasses the Arctic and boreal regions of Alaska, USA, and the western provinces of Canada, North America. Core and Extended study regions have been designated within this Domain. For user convenience, the boundaries of the Core and Extended regions are provided in both a vector representation (Shapefile) and a raster representation (GeoTIFF at 1,000-meter pixel resolution).

• The Core Region encompasses a range of landscapes, with areas that are rapidly changing in complex ways in response to global-scale climate change and regional-scale disturbances as well, as others that are not - a combination that will allow for the studies on both vulnerability and resilience.
• The Extended Region, outside of the Core Region, is needed for study of a subset of important changes that are unique to these regions (for example, insect outbreaks and forest dieback in the southern boreal forest). The Extended Region provides additional opportunities for research where environmental conditions are considered to be antecedent to those in the Core Region, as well as to collaborate on research being sponsored by partners.

Second, a Standard Reference Grid System has been developed to cover the entire Study Domain and also extends to the eastern portion of North America to accommodate wider-ranging studies. This Reference Grid is similar to the MODIS tiling scheme and is provided as a nested pair of polygon grids at scales of 240- and 30-meter spatial resolution to model MODIS and Landsat products. A shapefile is provided for each grid.

Note that the designated standard projection for the ABoVE Study Domain and the Reference Grid products is the Canadian Albers Equal Area projection. 

The domain for the ABoVE study area is over 6.3 x 10⁶ km². Within the ABoVE campaign, many thematic data products will be generated from field measurements, flux towers, airborne remote sensors and satellite remote sensing data. The data sets will range considerably in resolution, format, geographic extent, projection and/or reference system.

The standardized Reference Grid and projection will enable researchers to align and subdivide data products in order to facilitate archiving and distribution of datasets (both for long-term archiving of the data and near-term use throughout the campaign’s duration), and simplifies data standardization for scientific analysis within ABoVE.

Spatial Coverage:  Boreal and Tundra regions of North America -- covering all of Alaska and all provinces of Canada

Spatial Resolution:  The Core and Extended regions raster representation is provided at 1,000-meter pixel resolution.

Temporal Coverage:  20140101 – 20211231

Temporal Resolution:  Not Applicable

 

Study Area:

Site (Region)	Westernmost Longitude	Easternmost Longitude	Northernmost Latitude	Southernmost Latitude
ABoVE Study Domain	-176.124747	-66.917776	81.608577	39.415027
Standard Reference Grid	-177.469005	-16.792179	82.484482	34.058481

 

 

Data File Information:

Three data files are distributed with this data set: (1) a compressed shapefile (ABoVE_Study_Domain.zip) contains a vector representation of the Core and Extended study regions; (2) a GeoTIFF (ABoVE_Study_Domain.tif) file that is a raster representation of the Core and Extended study regions at 1,000-meter pixel resolution; and (3) a compressed (ABoVE_Grid_240m_and_30m.zip) file containing shapefiles for the 240- and 30-meter spatial resolution nested Standard Reference Grids.

File name	Description
ABoVE_Study_Domain.zip	ABoVE Study Domain as a vector file. When unzipped, this file provides the shape file ABoVE_Study_Domain.shp with the core and extended regions designated.
ABoVE_Study_Domain.tif	ABoVE Study Domain as a raster file. This file provides a raster representation of the core and extended ABoVE study domain.
ABoVE_Grid_240m_and_30m.zip	ABoVE reference grids. When unzipped, this file provides two shape files; ABoVE_240mgrid_tiles.shp and ABoVE_30mgrid_tiles.shp.

 

Variables in the Data Files

Table 1. Variables in the shapefile ABoVE_Study_Domain.shp

Variable	Unit	Description
Region		A text field indicating the Core and Extended Region Polygons
Shape_Leng	m	The geometric length of the Core and Extended Region Polygons (in meters)
Shape_Area	m	The geometric area of the Core and Extended Region Polygons (in sq meters)

 

Table 2. Variables in the raster file ABoVE_Study_Domain.tif.  No data is represented as 127.

Variable	Description
Value	A unique value representing the core (Value = 1) and extended (Value = 2) ABoVE Study Domain.
Count	The number of 1000 meter pixels for each unique Value (study domains)

 

 

Table 3. Variables in the files ABoVE_240mgrid_tiles.shp and ABoVE_30mgrid_tiles.shp

Variable	Description
UID	A unique ID for each grid cell
Ahh	The grid cell in the horizontal direction in the 240 m tile scheme with values ranging from 0 (left) to 5 (right)
Avv	The grid cell in the vertical direction in the 240 m tile scheme with values ranging from 0 (top) to 3 (bottom)
Bh	The grid cell in the horizontal direction in the 30 m tile scheme with values ranging from 0 (left) to 5 (right) nested within each of the larger Ahh grid cells.
Bv	The grid cell in the vertical direction in the 30 m tile scheme with values ranging from 0 (top) to 5 (bottom) nested within each of the larger Avv grid cells.

 

 

Spatial Reference Properties:  All Files

A Standard Projection has been chosen for all ABoVE data products. 

Projected
Geographic Coordinate Reference:  GCS_North_American_1983
Projection: Albers Equal Area Conic

 

The Canadian Albers Equal Area Conic projection system and parameters:

WKID (EPSG): 102001 Authority: ESRI

Projection: Albers Conic Equal Area
False_Easting: 0.0
False_Northing: 0.0
Central_Meridian: -96.0
Standard_Parallel_1: 50.0
Standard_Parallel_2: 70.0
Latitude_Of_Origin: 40.0
Linear Unit: Meter (1.0)

Geographic Coordinate System: GCS_North_American_1983
Angular Unit: Degree (0.0174532925199433)
Prime Meridian: Greenwich (0.0)
Datum: North_American_1983
    Spheroid: GRS_1980
        Semimajor Axis: 6378137.0
        Semiminor Axis: 6356752.314140356
        Inverse Flattening: 298.257222101

 

Spatial Data Properties: Raster file - GeoTIFF ABoVE_Study_Domain.tif

Spatial Representation Type: Raster
Pixel Depth: 8 bit
Pixel Type: byte
Number of Bands: 1
Band Information: ABoVE Study Domain
Raster Format: geoTIFF
No Data Value: 127
Scale Factor: none
Offset: none

Number Columns: 4,022
Column Resolution: 1,000 meter
Number Rows: 3,565
Row Resolution: 1,000 meter

Extent in the items coordinate system
North: 4562535.093300
South: 997535.093300
West: -3398274.762900
East: 623725.237100

xll corner: -3398274.762900
yll corner: 997535.093300
Cell Geometry: area
Point in Pixel: center

 

 

ABoVE Study Domain

The core and extended regions within the ABoVE Study Domain provide the opportunity to carry out research needed to address key research questions and objectives for understanding how environmental change is causing changes to social-ecological systems across the Arctic and boreal region of western North America.

• The Core Region of the Study Domain captures the regional-scale variation in surface and atmospheric conditions necessary for the research addressing the second tier science questions and objectives of ABoVE. The Core Region encompasses a range of landscapes, with areas that are rapidly changing in complex ways in response to global-scale climate change and regional-scale disturbances as well, as others that are not - a combination that will allow for the studies on both vulnerability and resilience.
• The Study Domain also includes an Extended Region outside of the Core Region that is needed for study of a subset of important changes that are unique to these regions (for example, insect outbreaks and forest dieback in the southern boreal forest). The Extended Region provides additional opportunities for research where environmental conditions are considered to be antecedent to those in the Core Region, as well as to collaborate on research being sponsored by partners.
•  

ABoVE Reference Grids

The ABoVE field campaign will provide the opportunity to expand and coordinate a set of focused, interdisciplinary research activities designed to further understand the causes and consequences of change in the social-ecological systems of the Arctic and boreal regions of western North America. The campaign is expected to result in the development of multiple geospatial datasets. To facilitate data interoperability, a standard projection and reference grid have been proposed to cover the ABoVE study domain. 

Thematic data products will be generated from field measurements, flux towers, airborne remote sensors and satellite remote sensing data. The datasets will range considerably in resolution, format, geographic extent, projection and/or reference system. This variability in ABoVE datasets is likely to place a considerable burden on individual researchers as they will need to standardize the incoming datasets to support geospatial analysis, thus leading to duplicated effort across research groups utilizing these products. This duplication of effort will continue to propagate as outcomes of scientific analysis from individual research groups will require subsequent standardization to support their further inclusion in ABoVE science projects. 

Implementing a standard projection and grid enables the producers of the data to align and subdivide data products in order to ease archiving and distribution of datasets (both for long-term archiving of the data and near-term use throughout the campaign’s duration), and simplifies data standardization for scientific analysis within ABoVE. This compatibility across multiple datasets facilitates interoperability of the datasets in scientific analysis, and is an important benefit of the standardized projection and reference grid.

Additionally, it is expected that many data products will be generated with medium to fine resolution (30m spatial resolution or less) imagery and hence would be too large to distribute to users as single files covering the entire study region. Where the projection provides a mechanism to ensure that the products are geometrically compatible, the reference grid provides a standardized way to break the files up into units that are easy to download and manipulate by the researchers.

Gridded ABoVE datasets of the extent larger than 100 X 100 km² are to be produced in this grid and projection (this is roughly a Landsat tile). It is recognized that, at very high resolution, reprojection of original data can result in substantial special shifts in orientation, location, and shape of small objects; therefore, ABoVE science team members are encouraged to submit their fine-scale datasets in the original projection in addition to the ABoVE grid format (if the extent of their dataset is greater or equal to 10,000 km²) or only in the original projection if it is smaller than that size.

 

Reference Grid Naming Convention

The reference grid naming convention is modeled after the MODIS grid using horizontal (h) and vertical (v) offsets from the upper left corner to describe the tile. For example in Figure 1 the large grid tile in the upper left corner is referred to as “h0v0” and the tile in the lower right corner is referred to as “h5v3”. For each of the large tiles there is a series of small tiles nested inside. The large grid is referred to as “A” and the small grid is referred to as “B”. This yields a naming convention such as:

ABoVE.water.2001001.Ah0v0.Bh2v3.001.2014075120101.hdf
Where:
     ABoVE – refers to the campaign
     Water – refers to the product ID or type
     2001001 – refers to the data reference date
     Ah0v0 – refers to the upper left tile in the “A” or larger grid
     Bh2v3 – refers to the central tile in the “B” or smaller grid
     001 – refers to the version of the product
     2014075120101 – is a production date for the product

Not applicable.

The ABoVE Reference Grid is applicable mainly for raster-based products derived for the study domain (but does not apply to circumpolar datasets). The grid has been designed to cover the entire study domain, and extends to the eastern portions of North America (see Figure 1) to accommodate any products that are looking at continental scale processes. This grid is similar to the MODIS tiling scheme and is a nested pair of grids provided at scales of 240 and 30 meter spatial resolution, such that products from MODIS and Landsat would be compatible within the grid. It is easily scalable for products of 30, 60, 90 meters etc., although for products smaller than 15 meters, it may be necessary to subdivide the grid to keep file sizes manageable.

The approach taken with the ABoVE reference grid and projection is modeled after the MODIS standard products. Below is a list of assumptions that were used when determining the projection and grid:

1. While the projection would be applicable to multiple data types, the grid would primarily be used for raster products produced over the study domain (not including circumpolar datasets).
2. To provide areal calculations from the data products we need to have the data in an equal area projection.
3. The products could range from fine spatial resolution (1 – 5m) to coarse spatial resolution (250m or more).
4. 30m will be a central spatial resolution.
5. Users of raster data can easily download files that are 300MB in size.