WorldView-2 Satellite Image Inventory for Timor-Leste

Inventory of satellite images from DigitalGlobe’s WorldView-2 satellite purchased by the NOAA Coral Reef Ecosystem Program for Timor-leste from Jan 26, 2010 to August 10, 2014. Images were acquired for purposes of deriving seafloor depths and benthic habitat classes for the nearshore waters (< 20m depths) of Timor-leste. In addition to the inventory, the dataset includes the regions of interest (ROI) defined by NOAA used to define the geographic areas to acquire the satellite images from DigitalGlobe, the boundary extent of the available images within each ROI, and the footprint (extent) of each image. The data within each satellite image is clipped to the ROI. The ROI, boundary, and footprint files are provided in shapefile format, and the inventory is provided as a text file, which corresponds to the footprints shapefile.

In 2011, NOAA and the United States Agency for International Development (USAID) Timor-Leste Mission formed a 5-year bi-lateral partnership agreement from 2012 to 2016, in support of the Government of Timor-Leste—particularly the Ministry of Agriculture and Fisheries (MAF)—by addressing significant information gaps in their nearshore marine ecosystems. Specifically, MAF asked NOAA to address the following questions:

1. Where are the nearshore marine resources?

2. What are the nearshore marine resources?

3. How are they changing over time and what threats are potentially causing these changes?

4. What approaches are needed to manage and conserve the nearshore marine resources?

With financial support from USAID and in-kind support from the NOAA Coral Reef Conservation Program (CRCP), the NOAA Coral Reef Ecosystem Program (NOAA-CREP) conducted baseline ecosystem assessment surveys to inform ecosystem-based management planning in Timor-Leste. The primary activities conducted by NOAA to answer these questions included:

1. satellite mapping of nearshore habitats,

2. conducting coral reef ecosystem assessments,

3. establishing ecological baselines for climate change, and

4. building management capacity by developing a spatial data framework

The satellite image inventory described herein resulted from the first activity to conduct satellite mapping for the nearshore waters around Timor-Leste.

Pacific Islands Fisheries Science Center. 2017. Interdisciplinary baseline ecosystem assessment surveys to inform ecosystem-based management planning in Timor-Leste: Final Report. Pacific Islands Fisheries Science Center, PIFSC Special Publication, SP-17-002, 234 p. https://doi.org/10.7289/V5/SP-PIFSC-17-002.

The Region of Interest (ROI) and Boundary shapefiles contain information about the four regions in Timor-leste (north and south shores of mainland Timor-leste, the island of Atauro, and the district of Oecusse to the west of mainland Timor-leste). The footprint shapefile represents the extent of each satellite image. The inventory file (CSV) contains information about each satellite image, including the purchase/acquisition attributes, type of imagery, center points in UTM, azimuth and elevation of the sun and satellite sensor, cloud cover, and off nadir. It also includes whether the image was georeferenced by NOAA, and used to derive depths and habitat classes. The inventory files corresponds to the footprints shapefil.

While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.

Timor-Leste

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NOAA Coral Reef Ecosystem Program (CREP) Data Sharing Recommendations, version 9.0 updated August 12, 2015:

CREP welcomes the opportunity to collaborate on research issues contributing to the scientific basis for better management of marine ecosystems. CREP has a very diverse set of field activities that generates large volumes of data using an array of data collection protocols.

The following recommendations are for your consideration as you use this data:

1) Data analyses should take all field exigencies into account. The most effective way to do this would be active collaboration with CREP principal investigators.

2) In all presentations, product releases, or publications using data generated by CREP, proper acknowledgement of both CREP and the individuals responsible for data collection is expected. Citing the DOI (if available) is preferred, a non-DOI example is listed below.

3) If you collect or generate data for the same study areas, CREP requests that you share relevant information on complimentary data collections.

4) Those receiving data are strongly urged to inform the CREP Data Management Team of any errors and discrepancies that are discovered during the course of using these data. They are further urged to bring to the attention of the Team all problems and difficulties encountered in using these data. This information is necessary in order to improve the collections and to facilitate more efficient and economical data processing and retrieval. The users are asked to supply copies of any missing data that may be located, and to provide information as to significant subsets and special aggregations of data that are developed in using the material provided.

Example citation:

"This publication makes use of data products provided by the Coral Reef Ecosystem Program (CREP), Pacific Islands Fisheries Science Center (PIFSC), National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), with funding support from the United States Agency for International Development (USAID). The analysis and interpretations presented here are solely that of the current authors.”

Data can be accessed online via the NOAA National Centers for Environmental Information (NCEI) Ocean Archive

WorldView-2 imagery cannot be publicly redistributed per the license agreement with DigitalGlobe. Contact the NOAA Coral Reef Ecosystem Program for specific questions about the source imagery for TImor-leste at nmfs.pic.credinfo@noaa.gov.

Please cite NOAA Coral Reef Ecosystem Program (CREP) when using the data.

Example

Coral Reef Ecosystem Program; Pacific Islands Fisheries Science Center (2017). WorldView-2 Satellite Image Inventory for Timor-Leste. NOAA's National Center for Environmental Information. Dataset. https://www.fisheries.noaa.gov/inport/item/46151

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All satellite images associated with each region of interest (ROI) in Timor-leste are stored in a mosaic dataset in an ESRI file geodatabase. Within each mosaic dataset is the boundary (extent) of the available images for each region (exported to a shapefile) and the footprint for each image within the boundary (exported to shapefile). Within GIS, the footprints can be used to quickly identify the image files that fall within a geographic area of interest. The inventory, extracted from the footprints, provides information about which satellite images are available and where, as well as information about each image. The source mosaic dataset geodatbase is not useful unless the user has direct access to the satellite images. Contact NOAA for more information if access to the imagery is required.

The location information for some of the satellite images was inadequate; therefore, the images did not align properly with each other or with other data. The images were spatially adjusted (georeferenced) to align with ArcGIS basemaps—provided by ESRI with ArcGIS products (http://www.esri.com/data/basemaps). The georeferencing step was performed using the georeferencing tools in ArcGIS 10.X desktop software.

The pixel values of the WorldView-2 satellite images provided by DigitalGlobe are digital numbers (0-255), which have not been calibrated into physically meaningful units (i.e., solar radiance). The digital numbers must therefore be converted to capture the radiance at the satellite sensor using a calibration formula (Updike and Comp 2010). The satellite sensor is routinely calibrated, and thus the coefficients provided by DigitalGlobe (in the metadata files) are unique to each image. The conversion was conducted in ENVI (Environment for Visualizing Images) image analysis software provided by Harris Geospatial Solutions (http://www.harrisgeospatial.com/ProductsandTechnology/Software/ENVI.aspx).

WorldView-2 satellite imagery was acquired for nearshore waters along the coast of Timor-Leste from Jan 26 2010 to Aug 10, 2014. Complete coverage of the coastline with WorldView-2 satellite images was achieved. However, some images contain areas of high water column turbidity, clouds, whitewater, etc. that were masked out of the analyses due to a lack of reliable imagery of the seafloor for those areas. Multiple overlapping images of some portions of the shoreline enabled sections of different images to be extracted and used to patch holes in other images in some cases, in a process known as "cloud patching." This process enabled more complete coverage to be developed for the depths and/or habitats.

Pre-processing of all WorldView-2 satellite images was performed using the same methods to georeference, convert the digital numbers, mask out areas, and remove sun glint.

The satellite image inventory was inspected following completion of the final products, and prior to delivery of the final products to the in-country partners.

NOAA IRC and NOAA Fisheries ITS resources and assets.

The image catalog is stored as an ESRI file geodatabase (not available) and serves two purposes: 1) it is an inventory of all the satellite images purchased by NOAA for each region of interest (ROI) in Timor-Leste, and 2) it contains features associated with the images, including the ROI, the boundary extent of the available images within each ROI, and the footprints of each image (exported as shapefiles and publicly accessible). Within GIS, the footprints can be used to quickly identify the image files that fall within a geographic area of interest.

Furthermore, the inventory (extracted from the footprints shapefile) provides metadata for the imagery, and also indicates if the images were georeferenced and used to derive depths or habitat classes.