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White Paper

PlanetDEM 30 Plus

PlanetObserver

10/12/2015

PlanetObserver France – www.planetobserver.com – [email protected] – Tel. +33 4 73 44 19 00

http://www.planetobserver.com/

mailto:[email protected]

White Paper – PlanetDEM 30 Plus – PlanetObserver

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1. Introduction

PlanetObserver presents PlanetDEM 30 Plus, a new Digital Elevation Model (DEM) offering global

coverage and reliable data at 30-meter resolution.

Background information

The NASA Shuttle Radar Topographic Mission (SRTM) has provided digital elevation data for all land

between 56 degrees south and 60 degrees north latitude, which comprises 80% of Earth’s total

landmass.

The NASA has initially released the SRTM dataset at 3 Arc-Seconds (approx. 90 meters) for near-

global coverage. The latest SRTM data version released by the NASA offers 1 Arc-Second resolution

(approx. 30 meters) for the entire dataset.

The SRTM dataset at 1 Arc-Second is a void-filled elevation dataset processed by the NASA. Although

the product has been corrected, some tiles still contain voids and pervasive artifacts, pits and bumps.

The SRTM data coverage is limited up to 60 degrees north and 56 degrees south. There is a lack of

coverage for all polar regions, including Norway and Sweden.

PlanetObserver has developed PlanetDEM 30 Plus, a new high quality elevation dataset offering 30-

meter resolution globally. PlanetDEM 30 Plus is processed from SRTM 1 Arc-Second data thoroughly

corrected and combined with other source data. All input elevation data have been compiled and

extensively reprocessed in order to offer a comprehensive global DEM with precise, corrected and

detailed information for the entire Earth.


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2. Product features

2.1 Global coverage

PlanetDEM 30 Plus elevation product covers all emerged lands (at 99%).

The above map shows SRTM data coverage in grey. It is limited to all land between 60 degrees north

and 56 degrees south latitude. All void areas and artifacts still present in the SRTM 30m elevation

dataset have been identified and corrected by using ASTER 30m elevation data. Corrected areas are

identified in orange on the map. Extensive data corrections have been carried out on all mountainous

regions across the world and in many desert areas in Africa and the Middle East.

On the map, blue areas correspond to the additional elevation data that have been compiled beyond

60° north latitude and 56° south latitude, areas uncovered by SRTM data. Those elevation data come

all from highly reliable sources.

2.2 Data sources

PlanetDEM 30 Plus is processed from different source data:

SRTM 1 Arc-Second (from 60 degrees north to 56 degrees south latitude) corrected with ASTER data in several places:

- Mountain areas: Andes, Alps, Himalayas, Southeast Asia, New Zealand, etc.

- Desert: Mauritania, Algeria, Libya, Egypt, Arabian Peninsula, etc.

For areas uncovered by SRTM data, accurate sources have been used:

- Antarctica: NSIDC (National Snow and Ice Data Center)

- Alaska: AGDC (Alaska Geospatial Data Clearinghouse)

- Canada: CDED (Canadian Digital Elevation Data) from Geobase

- Greenland, Iceland and Svalbard: topographic maps

- North Atlantic Islands, North Scandinavia, North Russia and North Siberia: Russian maps


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2.3 Corrections

PlanetDEM 30 Plus is a global elevation composite dataset processed with different source data.

Specific processing methods have been developed and applied, with a particular focus on edge

smoothing processing in order to produce a seamless and global DEM product.

Voids and artifacts due to clouds, sand and shadow effect still present in SRTM 1 Arc-Second dataset

have been carefully identified and corrected with ASTER 30m data.

2.4 Data specifications

PlanetDEM 30 Plus specifications in terms of vertical and horizontal accuracy are similar to SRTM

specs which are reported to be as follows:

- Vertical accuracy (LE95): 14 meters

- Horizontal accuracy (CE95): 10 meters

Oceans are set to 0 meter.

Negative values are present in areas under the sea level.

2.5 Data structure and format

Resolution :

PlanetDEM 30 Plus is available with a resolution of 1 Arc-Second (approx. 30m resolution).

File format :

The product is available in the following formats:

- GEOTIFF, 16 bit-format, divided in 5° x 5° tiles (18,000 x 18,000 pixels), for a total of 1,449

tiles ; total data size: 876 GB.

- DTED 2, divided in 1° x 1° tiles, for a total of 25,518 tiles; total data size: 397 GB.

Both file formats are supplied without tiles containing water only.

Tile naming :

For GeoTiff format, tiles are named as follows: PlanetDEM_30_Plus_(N or S)(yy)(W or E)(xxx).tif

N or S = tile upper latitude

W or E = tile left longitude

Projection :

The product comes in Geographic (latitude-longitude) projection, WGS84.

Other projections can be provided on demand for specific AOIs.


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3. Comparaison: PlanetDEM 30 Plus vs. SRTM

SRTM PlanetDEM 30 Plus

Desert, Egypt


Coastal area, Indonesia


Himalayas


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Alps


Fjords, Chile


Desert, Niger

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