A Continuous, Transboundary, 50-meter DEM for the Alaska Perhumid Coastal Temperate Rainforest (AKPCTR_DEM)

AKPCTR_DEM is a 50-meter resolution, bare-earth digital elevation model (DEM) in raster (geotiff) format. The perhumid (wettest) region of the North American coastal temperate rainforest (PCTR) extends along the coast of British Columbia and southeast Alaska between approximately 50.57 and 59.6 degrees north latitude.The extent of this dataset includes all of the Alaska and Canada watersheds that discharge into southeast Alaska coastal waters, which covers essentially the northern half of the PCTR.

General Methods:
Using Desktop ArcGIS version 10.3.1, the following three elevation datasets were combined to create a continuous DEM for the Alaska perhumid coastal temperate rainforest (AKPCTR) watersheds:

1) The 2-arc-second, 1:63360, USGS National Elevation Dataset (NED), downloaded 12/4/2008. Horizontal datum=NAD83; vertical datum=NGVD29; map units=decimal degrees; elevation units=meters. [Note: the term "3DEP" has replaced "NED."]

2) The 25-meter resolution, 1:20,000 British Columbia Terrain Resource Information Management (TRIM) DEM, downloaded 9/4/2009. Horizontal datum=NAD83; vertical datum=CGVD28; projection=BC Albers; map units=meters; elevation units=meters.

3) The 0.75-arc-second, 1:50,000 Canadian Digital Elevation Data (CDED) DEM for the Yukon Territory, downloaded 8/11/2015. Horizontal datum=NAD83; vertical datum=CGVD28; map units=decimal degrees; elevation units=meters.

The 3 DEMs were projected to a common coordinate system, resolution, and registration. The Canadian TRIM and CDED datasets were combined, then a program called “Merge” was used to join the Canada DEM to the NED. The different processing methods, scales, and vertical datums used to produce the source U.S. and Canada DEMs result in a visible seam where the 2 datasets are joined. The “Merge” program creates a smooth transition along the seam between the NED and Canada DEMs (see process steps for details).

Portions of the NED for Southeast Alaska have been updated with higher-resolution IfSAR and LiDAR data; however the vertical datum for this newer data is based on NAVD88. Using the updated portions of the NED would result in an AKPCTR DEM containing a mix of NAVD88, NGVD29, and CGVD28 elevations. There are no datum converters for Alaska to easily transform between NAVD88 and NGVD29 or CGVD28. To avoid the mix of vertical datums and to be more consistent with adjacent Canadian elevations in CGVD28, the older version of the NED (pre-LiDAR and IfSAR) was used. Source data for the Alaska and Canada DEMs range from the 1940's to 2002.

Data and Resources

Additional Info

Spatial resolution

50 meters

Credits

The following people worked on producing this data set:

  • The USGS Alaska Climate Science Center and USDA Forest Service provided funding for this project.
  • Frances Biles, USDS Forest Service, Pacific Northwest Research Station (produced AKPCTR_DEM.tif).
  • Dan Miller, TerrainWorks Inc. (created Merge program).
  • U.S. Geological Survey (USGS), EROS Data Center (source for 2-arc-second NED DEM dataset for Alaska).
  • British Columbia Ministry of Forests, Lands and Natural Resource Operations \u2013 GeoBC (source for 25-meter TRIM DEM dataset for British Columbia).
  • Sari Sanders and Andy MacKinnon, British Columbia Ministry of Forests, Lands and Natural Resource Operations, and Dan Sirk, Land Information Coordinator, Integrated Land Management Bureau, Vancouver Island Service Centre, British Columbia, Canada (provided assistance with BC TRIM DEM dataset).
  • Government of Canada; Natural Resources Canada (NRCan); Earth Sciences Sector; Canada Centre for Mapping and Earth Observation (source for 1:50k CDED DEM dataset for Yukon Territory).
Field Value
Source http://data.snap.uaf.edu/data/Base/Other/AKPCTR_DEM/
Maintainer Frances Biles
Version 1.0
access_constraints ["AKPCTR_DEM was created using funding from the U.S. Government and can be used without additional permissions or fees. Please cite this dataset if it is used in a publication, presentation, or other research product. A suggestion for the general form of the citation is as follows: Data Product Creator, Year of Data Publication, Title of Data Product, Publisher, Data Product Identifier (DOI or download link).", "The portion of AKPCTR_DEM covering Alaska, USA used source data produced by the U.S. Geological Survey. These data are covered under the USGS disclaimer (https://www.doi.gov/disclaimer) and are considered to be in the U.S. public domain and can be used without restriction (https://www2.usgs.gov/visual-id/credit_usgs.html).", "The portion of AKPCTR_DEM covering British Columbia, Canada used source data produced by the British Columbia Ministry of Forests, Lands and Natural Resource Operations \u2013 GeoBC. Use of this data is covered under the \"Open Government License - British Columbia,\" which can be viewed here: http://www2.gov.bc.ca/gov/content/governments/about-the-bc-government/databc/open-data/open-government-license-bc.", "The portion of AKPCTR_DEM covering the Yukon Territory, Canada used source data produced by the Government of Canada; Natural Resources Canada; Earth Sciences Sector; Canada Centre for Mapping and Earth Observation (source for 1:50k CDED DEM dataset for Yukon Territory). These data are licensed under the \"Open Government Licence \u2013 Canada,\" which can be viewed here: http://open.canada.ca/en/open-government-licence-canada."]
bbox-east-long -124.91369
bbox-north-lat 61.83026000000001
bbox-south-lat 54.1516
bbox-west-long -141.2049
contact-email fbiles@fs.fed.us
coupled-resource []
credits ["The USGS Alaska Climate Science Center and USDA Forest Service provided funding for this project.", "Frances Biles, USDS Forest Service, Pacific Northwest Research Station (produced AKPCTR_DEM.tif).", "Dan Miller, TerrainWorks Inc. (created Merge program).", "U.S. Geological Survey (USGS), EROS Data Center (source for 2-arc-second NED DEM dataset for Alaska).", "British Columbia Ministry of Forests, Lands and Natural Resource Operations \u2013 GeoBC (source for 25-meter TRIM DEM dataset for British Columbia).", "Sari Sanders and Andy MacKinnon, British Columbia Ministry of Forests, Lands and Natural Resource Operations, and Dan Sirk, Land Information Coordinator, Integrated Land Management Bureau, Vancouver Island Service Centre, British Columbia, Canada (provided assistance with BC TRIM DEM dataset).", "Government of Canada; Natural Resources Canada (NRCan); Earth Sciences Sector; Canada Centre for Mapping and Earth Observation (source for 1:50k CDED DEM dataset for Yukon Territory)."]
dataset-reference-date [{"type": "publication", "value": "2016-08-03T00:00:00"}]
download-url http://data.snap.uaf.edu/data/Base/Other/AKPCTR_DEM/
frequency-of-update unknown
graphic-preview-description thumbnail
graphic-preview-file DEM_thumbnail_s.png
graphic-preview-type png
guid 85ae3c2d-5a71-4675-923c-bf6ed85a460a
licence ["Different vertical datums are used in this DEM. Canadian elevations are referenced to CGVD28. U.S. elevations are referenced to NGVD29, with the exception of an area at the southern tip of Baranof Island having bounding coordinates of LR=56 degrees N latitude, 133.998993 degrees west longitude; UL=57 degrees N latitude, 135.001007 degrees W longitude. This area is covered by USGS 1:63,360 topographic map \"Port Alexander B3\" (PAXB3). The elevations for PAXB3 came from the Shuttle Radar Topography Mission (SRTM), which uses a vertical datum of NAVD88.", "CGVD28 elevations are slightly lower than NGVD29 heights. These differences are thought to be small (they are typically less than 0.5 feet in the Great Lakes area), but it is not clear what the true differences between the two datums are in Alaska. Where the NED and TRIM DEMs overlap along the international border, NED heights were 12 meters higher on average, with differences ranging from -880 meters (TRIM higher than NED) to 860 meters (NED higher than TRIM). The \"Merge\" program was used to smooth the seam between the Canadian and U.S. DEMs to create a more visually pleasing transition and help ensure that water flows towards the coast.", "Data anomalies exist scattered throughout the U.S. and Canada DEMs, especially in the high-elevation transboundary area. The majority of these anomalies are: 1) areas where it appears that lower-resolution source data was used to fill in areas that otherwise lacked adequate coverage, 2) data processing artifacts such as grid-like patterns or stepped contour patterns, 3) pits and unnatural, rough surfaces (due to processing errors or data quality issues) over glaciated areas where it appears that ASTER or SRTM data was used 4) visible seams along source map tile boundaries. Issues 1 to 3 are primarily in areas where glaciers are present."]
license Creative Commons Attribution 4.0
license_url http://creativecommons.org/licenses/by/4.0/
metadata-date 2016-10-06T17:02:05
metadata-language
progress completed
resource-type
responsible-party [{"name": "USDA Forest Service", "roles": ["originator"]}]
spatial {"type": "Polygon", "coordinates": [[[-141.2049, 54.1516], [-124.91369, 54.1516], [-124.91369, 61.83026], [-141.2049, 61.83026], [-141.2049, 54.1516]]]}
spatial-data-service-type
spatial-reference-system 26931
spatial-resolution 50
spatial-resolution-units meters
spatial_harvester true