# DEA Summary Product Grid (Collection 3)¶

## Introduction¶

Digital Earth Australia (DEA) maintains and distributes collections of Satellite derived information sourced from a growing number of different Satellite missions.

Previously, as part of DEA’s Landsat Collection 2, all Landsat Analysis Ready Data (ARD) was re-projected from native Universal Transverse Mercator (UTM) to Australia Albers (EPSG:3577) and tiled to a common $$100km^2$$ grid. As a result, all products, single-observation and summary, were published in a common projection and grid tiling scheme.

As part of DEA Landsat Collection 3, ARD and single-observation derivative products are distributed in their native UTM projection in an effort to reduce:

• complexity of our pipelines,

• reduce size on disk,

• lossy re-projection of data from native coordinate reference system.

In an effort to make information across Australia comparable, continental-scale, statistical summary products are produced in a common grid based upon Australian Albers (Albers Collection 3 grid). This page describes how we developed this grid and how it differs from the previous Australian Albers grid (Albers Collection 2 grid).

## How did we develop the new Collection 3 grid?¶

In developing this new grid, we had a number of goals:

• be compatible with the new resolution of Landsat ($$30m^2$$ from $$25m^2$$)

• be interoperable between both Landsat ($$30m^2$$) and Sentinel-2 ($$10m^2$$, $$20m^2$$ and $$60m^2$$)

• have a naming convention that was non-negative, removing the need for plus and minus symbols that can be problematic for some applications

The tile size is defined as $$96km^2$$, for Landsat this will result in a raster size of $$3200*3200$$ pixels of $$30m^2$$. In the case of Sentinel-2, this will result in a raster size of $$9600*9600$$ pixels of $$10m^2$$.

For compatibility with file system and web access tools and protocols, the grid has been defined to be non-negative, with the x00,y00 cell located in the South-Western corner of the grid, and positive numbers progressing Northward and Eastward.

The extent of this grid is based upon the maximal extents of:

• GDA94 / Australian Albers projection coordinate reference system (EPSG:3577),

• Digital Earth Australia’s Landsat collection 3,

• Digital Earth Australia’s Sentinel-2 Collection,

• With a 3-cell buffer for future growth.

Shown here is an image of the new grid in EPSG:3577 projection, with tiles shown where we expect to have land imagery available.

## How can I use this grid?¶

This tiling grid scheme has been used to subdivide processing and storage of our continental products.

This tiling grid can be used as an overlay in other spatial systems to determine the xMyN reference of a given area of interest from within a DEA Collection 3 summary product.

Unfortunately, there is no one-to-one mapping of the new Albers Collection 3 grid to the old Albers Collection 2 grid.