# Auxiliary data

## Base layers from auxiliary data (visualisation)

Different auxiliary datasets are offered in the ESA Charter Mapper as static layers to be used only for visualisation purposes as alternative (or complementary) base layers to the default one.

The list of auxiliary data base layers that are available is the following:

• Copernicus DEM1

• ESA World Cover2

• JRC Global Surface Water3,4 (Transitions, Change, Seasonality, Recurrence, Extent, Occurrence),

• DLR World Settlement Footprint 20195

• NASA Gridded Population of the World 20206

The below figure shows an example of visualisation of the ESA World Cover Base layer in the map.

Using the show layer info button next to the title of the layer in the list it is possible to superimpose each auxiliary base layer to the default basemap by setting a desired level of transparency.

For each base layer it is also possible to display the related legend by clicking on the show layer info button.

Opacity can be also used to superimpose multiple auxiliary data layers, as shown in the below figure between the GSW Water Occurrence and the WSF 2019 layers near the Gabon coast.

Warning

The ESA Charter Mapper relies on the external map / tile servers provided by the providers of the Auxiliary datasets.

## Auxiliary Datasets (processing and visualisation)

The ESA Charter Mapper also offers auxiliary data in the form Datasets including single or multiple assets to be used for visualization and processing.

## List of offered Auxiliary Datasets

Selected auxiliary datasets are the following:

• Copernicus DEM1,

• ESA Global Land Cover 20202,

• Global Surface Water 1984-20203,4,

• World Settlement Footprint 20195,

• WorldPop Population density 20207.

The list of auxiliary assets in COG format is given in the following table.

Dataset Description Assets included Res (m) Notes
Copernicus DEM (GLO-30) DSM at 30m resolution Single-band asset 30
ESA WorldCover Land Cover for 2020 from S1 and S2 data Single-band asset with LC 11 classes 10
Global Surface Water Globally spatial and temporal distribution of water surfaces over the past 37 years Six single-band assets for GSW: Occurrence, Occurrence Change Intensity, Seasonality, Recurrence, Transitions, and Maximum Water Extent. 25
World Settlement Footprint Binary mask outlining the extent of human settlements globally (2019) Single-band asset 10 True value 255
WorldPop Population density UN Adjusted 2020 Single-band asset 100

Table 1 - Auxiliary data specifications.

## Systematic Dataset creation for the activation workspace

For the auxiliary datasets to be made available for processing, the data in its original format is gathered from the source, either external or from a local repository, pre-processed to convert it in the format needed by the processing services (STAC+COG) and stored in the Activation storage space. This ensures its availability and usability for the full duration of the activation. Their reformatting in STAC+COG also enables visualisation via the platform tiler (i.e. the layer styling function).

Once an activation workspace is created, a background processing implements a mosaic over the call areas buffered envelope. As an example in the case of the areas defined in the [Act-756/Call-869] Tropical Storm Megi in the Philippines, the auxiliary datasets offered within the workspace do not have a global extension but cover only the portion of the Philippines surrounding the activation areas.

In particular, the creation of a mosaic for each auxiliary dataset is done by using a buffered polygon including all activation areas as shown in the below figure.

This polygon buffered with a certain distance (e.g. 0.05 degrees) is then used to select all the intersecting tiles. Therefore the resulting mosaic includes a wider area than the one shown in the below image with the rectangle in white. The mosaicking is triggered one by one systematically for all auxiliary datasets. Thus, in the activation workspace the users access a list of Auxiliary Datasets by clicking on the Aux Datasets data context upper menu.

Warning

The Aux Datasets data context button in the upper menu is currently under development. Thus, Auxiliary Datasets can temporarly found under Datasets. In this temporary situation please note that to filter Auxiliary Datasets from Calibrated EO Datasets in the Filter Criteria under the Satellite filter use the class auxiliary data.

Once the mosaicking is done and all resulting auxiliary datasets are published, PM/VAs can easily visualise the asset in the map at full resolution, change layer styling and consult the values directly in the map as shown in the below figure.

Auxiliary Datasets appear as multiple features under Results in the left panel as shown in the below image.

After selecting one of the features in the result list the user can see in the map each auxiliary dataset one by one. In a similar manner the user can drag and drop the selected Dataset as input to a processing service (when relevant and supported by the processing service). In case of the Global Surface Water auxiliary data the mosaicked Dataset includes multiple assets (Transitions, Change, Seasonality, Recurrence, Extent, Occurrence).

1. Copernicus DEM global 30m (GLO-30) DSM at 30m resolution. More info at: spacedata.copernicus.eu

2. ESA World Cover, global land cover product at 10 m resolution for 2020 based on Sentinel-1 and 2 data with 11 LC classes. More info at: esa-worldcover.org

3. Pekel, JF., Cottam, A., Gorelick, N. et al. High-resolution mapping of global surface water and its long-term changes. Nature 540, 418–422 (2016). DOI: 10.1038/nature20584

4. Global Surface Water 1984-2020, Occurrence, Occurrence change intensity, Seasonality, Recurrence, Transitions, and Maximum water extent. More info at: global-surface-water.appspot.com