Stereo-Photogrammetric Digital Elevation/Surface Models
The Digital Elevation Models (DEMs) provided here are gridded surface elevation data constructed from overlapping pairs high-resolution (~0.5 m) images acquired by the DigitalGlobe, Inc. Worldview-1 and 2 satellites through the NGA EnhancedView license. The DEMs are built using photogrammetric techniques in which common features are identified in each image and are used to model the relative three dimensional position of the terrain. These DEMs are constructed without ground control and rely on the satellite positioning model (also called the Rational Function Mode, or RFM) to locate the surface in space. The accuracy of the DEM is primarily limited by the accuracy of the rational polynomial coefficients, or RPC’s, used in the RFM model, and is expected to be several meters in the vertical dimension. Additional errors in the DEM arise from failure in the matching software due to clouds, shadows and lack of contrast.
Please be aware that you will be asked to register before viewing or downloading any DEM product. However, all elevation data are available at no cost.
The PGC provides DEMs from several processing methods:
1. Surface Extraction with TIN-based Search-space Minimization (SETSM) from M.J. Noh and I. Howat (Ohio State University)
These DEMs were created using the Surface Extraction from TIN-based Search-space Minimization (SETSM) algorithm developed at the Byrd Polar Research Center, Ohio State University with funding from NASA. SETSM uses a pyramiding approach to efficiently generate surfaces from stereo imagery using only the sensor’s Rational Function Model (RFM) and Rational Polynomial Coefficients (RPC). The software is parallelized and runs in the Matlab environment using embedded C-subroutines for efficiency. More detail on SETSM and access to the data below.
Noh, M.J., I.M. Howat, Automated stereo-photogrammetric DEM generation at high latitudes: Surface Extraction from TIN-Based Search Minimization (SETSM) validation and demonstration over glaciated regions, GIScience and Remote Sensing, doi:10.1080/15481603.2015.1008621
2. Ames Stereo Pipeline (ASP)
The Flade Isblink DEMs are data products from Flade Isblink, Greenland. These datasets are the results from an upcoming Nature paper from Mike Willis, Brad Herried, and Mike Bevis. The 22 DEMs (2012-14) available showcase the recharge of subglacial lake, evidence through a surficial depression as scene in the DEMs.
3. Desktop Remote Sensing Software (ERDAS, etc.) (currently no data available)
What geographic areas are covered?
Currently, a limited set of data is available, primarily on the North Slope of Alaska and western Greenland. We plan to expand the data coverage over time.
What products are available?
The SETSM surface models are distributed as segmented tiles within the full area mosaic using the PGC Arctic and Antarctic tiling scheme. The files are 32-bit GeoTIFFs with projections dependent on the location (EPSG:3031 for Antarctica, EPSG:3413 for the Arctic). Along with each DEM file are included acquisition date and data coverage raster files of the same dimensions of the DEM. The acquisition date file gives the acquisition day of each pixel of the DEM mosaic. The data coverage file is a binary mask with 1’s for pixels that contain at least one Triangulated Irregular Network (TIN) elevation point and zero for pixels that were only interpolated. This mask can be applied to compare the DEM accuracy with ground control, such as LiDAR and GPS surveys.
ASP and other products are currently unavailable. We expect non-mosaicked "standard" products (e.g. full strip or scene DEMs) to be availalbe upon a full release in December 2013. That release will include a robust user interface, programmatic access, and broader temporal and spatial data coverage.
Are there licensing restrictions?
All of the elevation data are publicly available. However, the optical imagery that the DEMs are derived from are under licensing restrictions and are not available to download. For more information on obtaining the optical imagery, please contact Paul Morin at the Polar Geospatial Center.
How do I get the data?
There is a beta portal for data discovery and download. You must register your name, email address, and home institution to access the data pages. Currently, only BETA SETSM mosaics for the Arctic are available (limited geographic coverage). We plan to release more spatial coverage and product types during the full release in December 2013.
Who created the DEMs?
These DEMs are distributed and created by the Polar Geospatial Center and the Byrd Polar Research Center Glacier Dynamics Group. Development of SETSM was funded under NASA Award NNX10AN61G. Data processing was supported by a Discovery User resource allocation grant to I. Howat by the Ohio Supercomputing Center. Distribution is funded under NSF Cooperative Agreement 1043681. For more questions about the SETSM surface models, please contact Myoung-Jong Noh at The Ohio State University.
How should I cite the data?
Acknowledgment for the SETSM surface models should be present in any publication, proceeding, presentation, etc. You must notify Ian Howat at The Ohio State University if you are to use the surface models in any of those forms. Please note, the SETSM mosaics are currently in BETA release and the dataset authors make no guarantees of product accuracy and the authors cannot be held liable for any errors, events, etc. arising from its use.