This is a tiled collection of the 3D Elevation Program (3DEP) and is one meter resolution. The 3DEP data holdings serve as the elevation layer of The National Map, and provide foundational elevation information for earth science studies and mapping applications in the United States. Scientists and resource managers use 3DEP data for hydrologic modeling, resource monitoring, mapping and visualization, and many other applications. The elevations in this DEM represent the topographic bare-earth surface. USGS standard one-meter DEMs are produced exclusively from high resolution light detection and ranging (lidar) source data of one-meter or higher resolution. One-meter DEM surfaces are seamless within collection projects, but, not necessarily seamless across projects. The spatial reference used for tiles of the one-meter DEM within the conterminous United States (CONUS) is Universal Transverse Mercator (UTM) in units of meters, and in conformance with the North American Datum of 1983 ...

This dataset contains the Digital Elevation Model (DEM) for South America from the Hydrologic Derivatives for Modeling and Analysis (HDMA) database. The data were developed and distributed by processing units. There are 10 processing units for South America. The distribution files have the number of the processing unit appended to the end of the zip file name (e.g. sa_dem_3.zip contains the DEM data for unit 3-2). The HDMA database provides comprehensive and consistent global coverage of raster and vector topographically derived layers, including raster layers of digital elevation model (DEM) data, flow direction, flow accumulation, slope, and compound topographic index (CTI); and vector layers of streams and catchment boundaries. The coverage of the data is global (-180º, 180º, -90º, 90º) with the underlying DEM being a hybrid of three datasets: HydroSHEDS (Hydrological data and maps based on SHuttle Elevation Derivatives at multiple Scales), Global Multi-resolution Terrain Eleva ...

The High Resolution Digital Elevation Model (HRDEM) product is derived from airborne LiDAR data (mainly in the south) and satellite images in the north. The complete coverage of the Canadian territory is gradually being established. It includes a Digital Terrain Model (DTM), a Digital Surface Model (DSM) and other derived data. For DTM datasets, derived data available are slope, aspect, shaded relief, color relief and color shaded relief maps and for DSM datasets, derived data available are shaded relief, color relief and color shaded relief maps. The productive forest line is used to separate the northern and the southern parts of the country. This line is approximate and may change based on requirements. In the southern part of the country (south of the productive forest line), DTM and DSM datasets are generated from airborne LiDAR data. They are offered at a 1 m or 2 m resolution and projected to the UTM NAD83 (CSRS) coordinate system and the corresponding zones. The datasets at a 1 m resolution cover an area of 10 km x 10 km while datasets at a 2 m resolution cover an area of 20 km by 20 km. In the northern part of the country (north of the productive forest line), due to the low density of vegetation and infrastructure, only DSM datasets are generally generated. Most of these datasets have optical digital images as their source data. They are generated at a 2 m resolution using the Polar Stereographic North coordinate system referenced to WGS84 horizontal datum or UTM NAD83 (CSRS) coordinate system. Each dataset covers an area of 50 km by 50 km. For some locations in the north, DSM and DTM datasets can also be generated from airborne LiDAR data. In this case, these products will be generated with the same specifications as those generated from airborne LiDAR in the southern part of the country. The HRDEM product is referenced to the Canadian Geodetic Vertical Datum of 2013 (CGVD2013), which is now the reference standard for heights across Canada. Source data for HRDEM datasets is acquired through multiple projects with different partners. Since data is being acquired by project, there is no integration or edgematching done between projects. The tiles are aligned within each project. The product High Resolution Digital Elevation Model (HRDEM) is part of the CanElevation Series created in support to the National Elevation Data Strategy implemented by NRCan. Collaboration is a key factor to the success of the National Elevation Data Strategy. Refer to the “Supporting Document” section to access the list of the different partners including links to their respective data.

This dataset contains the Digital Elevation Model (DEM) for North America from the Hydrologic Derivatives for Modeling and Analysis (HDMA) database. The DEM data were developed and distributed by processing units. There are 13 processing units for North America. The distribution files have the number of the processing unit appended to the end of the zip file name (e.g. na_dem_3_2.zip contains the DEM data for unit 3-2). The HDMA database provides comprehensive and consistent global coverage of raster and vector topographically derived layers, including raster layers of digital elevation model (DEM) data, flow direction, flow accumulation, slope, and compound topographic index (CTI); and vector layers of streams and catchment boundaries. The coverage of the data is global (-180º, 180º, -90º, 90º) with the underlying DEM being a hybrid of three datasets: HydroSHEDS (Hydrological data and maps based on SHuttle Elevation Derivatives at multiple Scales), Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010) and the Shuttle Radar Topography Mission (SRTM). For most of the globe south of 60º North, the raster resolution of the data is 3-arc-seconds, corresponding to the resolution of the SRTM. For the areas North of 60º, the resolution is 7.5-arc-seconds (the smallest resolution of the GMTED2010 dataset) except for Greenland, where the resolution is 30-arc-seconds. The streams and catchments are attributed with Pfafstetter codes, based on a hierarchical numbering system, that carry important topological information.

This collection is a legacy product that is no longer supported. It may not meet current government standards. The Canadian Digital Elevation Model (CDEM) is part of Natural Resources Canada's altimetry system designed to better meet the users' needs for elevation data and products. The CDEM stems from the existing Canadian Digital Elevation Data (CDED). In these data, elevations can be either ground or reflective surface elevations. A CDEM mosaic can be obtained for a pre-defined or user-defined extent. The coverage and resolution of a mosaic varies according to latitude and to the extent of the requested area. Derived products such as slope, shaded relief and colour shaded relief maps can also be generated on demand by using the Geospatial-Data Extraction tool. Data can then be saved in many formats. The pre-packaged GeoTiff datasets are based on the National Topographic System of Canada (NTS) at the 1:250 000 scale; the NTS index file is available in the Resources section in many formats.

1 arc-second (30m) raster topographical data from the National Elevation Dataset (NED) for the Baltimore MSA. The USGS National Elevation Dataset (NED) has been developed by merging the highest-resolution, best-quality elevation data available across the United States into a seamless raster format. NED is the result of the maturation of the USGS effort to provide 1:24,000-scale Digital Elevation Model (DEM) data with NAD83 datum for the conterminous US and Hawaii, and 1:63,360-scale DEM data with NAD27 datum for Alaska. This is part of a collection of 221 Baltimore Ecosystem Study metadata records that point to a geodatabase. The geodatabase is available online and is considerably large. Upon request, and under certain arrangements, it can be shipped on media, such as a usb hard drive. The geodatabase is roughly 51.4 Gb in size, consisting of 4,914 files in 160 folders. Although this metadata record and the others like it are not rich with attributes, it is nonetheless made available because the data that it represents could be indeed useful. This is part of a collection of 221 Baltimore Ecosystem Study metadata records that point to a geodatabase. The geodatabase is available online and is considerably large. Upon request, and under certain arrangements, it can be shipped on media, such as a usb hard drive. The geodatabase is roughly 51.4 Gb in size, consisting of 4,914 files in 160 folders. Although this metadata record and the others like it are not rich with attributes, it is nonetheless made available because the data that it represents could be indeed useful.

A Digital Elevation Model (DEM) is a digital data file containing an array of elevation information over a portion of the earth's surface. This array is developed using information extracted from digitized elevation contours from Primary Base Series (PBS) maps. FSTopo or PBS are 1:24,000 scale topographic maps. This dataset is a digital elevation model grid at a resolution of 10 meters by 10 meters. The data was originated from 1:24,000 scale topographic maps (primarily contours). The base data is in the form of an esri lattice file. Derived datasets include generated contours at 10, 25, and 50 meter intervals, degree slope, aspects, and a hillshade for topographic visualization.

River hydraulic geometry is an important input to hydraulic and hydrologic models that route flow along streams, determine the relationship between stage and discharge, and map the potential for flood inundation give the flow in a stream reach. Traditional approaches to quantify river geometry have involved river cross-sections, such as are required for input to the HEC-RAS model. Extending such cross-section based models to large scales has proven complex, and, in this presentation, an alternative approach, the Height Above Nearest Drainage, or HAND, is described. As we have implemented it, HAND uses multi-directional flow directions derived from a digital elevation model (DEM) using the Dinifinity method in TauDEM software (http://hydrology.usu.edu/taudem) to determine the height of each grid cell above the nearest stream along the flow path from that cell to the stream. With this information, and the depth of flow in the stream, the potential for and depth of flood inundation can be determined. Furthermore, by dividing streams into reaches or segments, the area draining to each reach can be isolated and a series of threshold depths applied to the grid of HAND values in that isolated reach catchment, to determine inundation volume, surface area and wetted bed area. Dividing these by length yields reach average cross section area, width, and wetted perimeter. Together with slope (also determined from the DEM) and roughness (Manning's n) these provide all the inputs needed for establishing a Manning's equation uniform flow assumption stage-discharge rating curve and for mapping potential inundation from discharge. This presentation will describe the application of this approach across the continental US in conjunction with NOAA’s National Water Model for prediction of stage and flood inundation potential in each of the 2.7 million reaches of the National Hydrography Plus (NHDPlus) dataset, the vast majority of which are ungauged. The continental US scale application has been enabled through the use of high performance parallel computing at the National Center for Supercomputing Applications (NCSA) and the CyberGIS Center at the University of Illinois.

Presentation at 2018 AWRA Spring Specialty Conference: Geographic Information Systems (GIS) and Water Resources X, Orlando, Florida, April 23-25, http://awra.org/meetings/Orlando2018/.

Abstract

This dataset and its metadata statement were supplied to the Bioregional Assessment Programme by a third party and are presented here as originally supplied.

MrVBF is a topographic index designed to identify areas of deposited material at a range of scales based on the observations that valley bottoms are low and flat relative to their surroundings and that large valley bottoms are flatter than smaller ones. Zero values indicate erosional terrain with values 1 and larger indicating progressively larger areas of deposition. There is some evidence that MrVBF values correlate with depth of deposited material.

The MrVBF product was derived from the Smoothed Digital Elevation Model (DEM-S; ANZCW0703014016), which is based on the 1 second resolution SRTM data acquired by NASA in February 2000.

Dataset History

The 1 second SRTM-derived Smoothed Digital Elevation Model (DEM-S; ANZCW0703014016).

MrVBF calculation

The MrVBF method is described in Gallant and Dowling (2003). It is based on slope and position in landscape (ranking within a 3- or 6-cell circular window) calculated from the original DEM and progressively generalised DEMs. The algorithm used to create this product is version 6g-a5, which is slightly different to that in the original paper.

Each value of MrVBF is associated with a particular scale and slope threshold. For each successive value the slope threshold halves and the scale triples. At each scale a location is considered erosional if it is high (ranked above the majority of the surrounding cells) or steep (slope greater than the threshold), and depositional otherwise. The largest value takes precedence at each location, so a value of zero indicates the site is considered to be erosional at all scales.

Value Threshold Resolution Interpretation

   slope (%)  (approx)

0 30 m Erosional

1 16 30 Small hillside deposit

2 8 30 Narrow valley floor

3 4 90

4 2 270 Valley floor

5 1 800 Extensive valley floor

6 0.5 2.4 km

7 0.25 7.2 km Depositional basin

8 0.125 22 km

9 0.0625 66 km Extensive depositional basin

MrVBF has been used with topographic wetness index (TWI) to predict soil depths; see McKenzie, Gallant and Gregory (2003) for details.

The MrVBF calculation was performed on 1°  1° tiles, with overlaps to ensure correct values at tile edges, for the finer scale steps (1 through 3). The coarser scale steps use lower resolution data so could be processed for the entire continent as a single piece, starting with a generalised version of DEM-S at 9 second resolution. The tiled processing clipped out the relevant parts of the 9 second results and combined them with the finer scale results from the 1 second DEM-S.

Dataset Citation

CSIRO (2016) AUS SRTM 1sec MRVBF mosaic v01. Bioregional Assessment Source Dataset. Viewed 18 June 2018, http://data.bioregionalassessments.gov.au/dataset/79975b4a-1204-4ab1-b02b-0c6fbbbbbcb5.

Abstract

This dataset and its metadata statement were supplied to the Bioregional Assessment Programme by a third party and are presented here as originally supplied

MrRTF is a topographic index designed to identify high flat areas at a range of scales. It complements the MrVBF index that is designed to identify areas of deposited material in flat valley bottoms. Unlike MrVBF, the MrRTF index does not have a clear link to landform processes but it has been found to be a useful adjunct to MrVBF in landform classification. Zero values indicate areas that are steep or low, with values 1 and larger indicating progressively larger areas of high flat land.

The 3 second resolution product was generated from the 1 second MrRTF product and masked by the 3" water and ocean mask datasets.

Dataset History

This dataset and its metadata statement were supplied to the Bioregional Assessment Programme by a third party and are presented here as originally supplied:

Data quality

Lineage:

Source data

1. The 1 second MrRTF product

2. 3 second resolution SRTM water body and ocean mask datasets

MrRTF calculation

The MrRTF and MrVBF method is described in Gallant and Dowling (2003). It is based on slope and position in landscape (ranking within a 3- or 6-cell circular window) calculated from the original DEM and progressively generalised DEMs. The algorithm used to create this product is version 6g-a5, which is slightly different to that in the original paper.

Each value of MrRTF is associated with a particular scale and slope threshold. For each successive value the slope threshold halves and the scale triples. At each scale a location is assigned the value for that scale if it is sufficiently high (ranked above the majority of the surrounding cells) and flat (slope less than the threshold), and zero otherwise. The largest value takes precedence at each location.

Value Threshold Resolution

   slope (%)  (approx)

0 30 m

1 16 30

2 8 30

3 4 90

4 2 270

5 1 800

6 0.5 2.4 km

7 0.25 7.2 km

8 0.125 22 km

9 0.0625 66 km

The 3 second version of MrRTF was derived from the 1 second MrRTF using the median value in each 3 x 3 group of 1 second cells.

Positional accuracy:

The horizontal positional error is the same as for the raw SRTM 1 second data, with 90% of tested locations within 7.2 m for Australia. See Rodriguez et al. (2006) for more information.

Attribute accuracy:

There is no clear geomorphic interpretation of the MrRTF index, so its accuracy is difficult to assess. Users are advised that the interpretation of the MrRTF index is likely to be sensitive to geomorphic context i.e. similar values mean different things in different areas. In some areas, high values of MrRTF index are associated with deeply weathered features where relatively flat areas high in the landscape have been preserved over a long period while surrounding areas have been eroded, exposing fresher material.

The caveats for MrVBF (which does have a reasonably consistent geomorphic interpretation) are repeated here for information:

* In areas dominated by aeolian transport the assumptions behind the method are not met, and dunes (for example) are represented as erosional features with MrVBF = 0.

* Alluvial and colluvial fans are depositional but stand above their surroundings so often appear as erosional features with MrVBF = 0.

Logical consistency:

This product is a consistent representation of terrain based on the information in DEM-S.

Completeness:

The MrRTF product covers the same area as the source DEM-S, which is virtually all of continental Australia and near coastal islands. Some tiles containing parts of mainland or pieces of islands were not supplied at 1 second resolution and are therefore missing, see DEM-S metadata for details.

Dataset Citation

CSIRO (2000) Multi-resolution Ridge Top Flatness at 3 second resolution CSIRO 20000211. Bioregional Assessment Source Dataset. Viewed 27 November 2017, http://data.bioregionalassessments.gov.au/dataset/d29afa3d-2b3e-41c1-8c3f-e1b2500f16cc.

Download In State Plane Projection Here The 2017 Digital Terrain Model (DTM) is a 2 foot pixel resolution raster in Erdas IMG format. This was created using the ground (class = 2) lidar points and incorporating the breaklines. The DTMs were developed using LiDAR data. LiDAR is an acronym for LIght Detection And Ranging. Light detection and ranging is the science of using a laser to measure distances to specific points. A specially equipped airplane with positioning tools and LiDAR technology was used to measure the distance to the surface of the earth to determine ground elevation. The classified points were developed using data collected in April to May 2017. The LiDAR points, specialized software, and technology provide the ability to create a high precision three-dimensional digital elevation and/or terrain models (DEM/DTM). The use of LiDAR significantly reduces the cost for developing this information. The DTMs are intended to correspond to the orthometric heights of the bare surface of the county (no buildings or vegetation cover). DTM data is used by county agencies to study drainage issues such as flooding and erosion; contour generation; slope and aspect; and hill shade images. This dataset was compiled to meet the American Society for Photogrammetry and Remote Sensing (ASPRS) Accuracy Standards for Large-Scale Maps, CLASS 1 map accuracy. The U.S. Army Corps of Engineers Engineering and Design Manual for Photogrammetric Production recommends that data intended for this usage scale be used for any of the following purposes: route location, preliminary alignment and design, preliminary project planning, hydraulic sections, rough earthwork estimates, or high-gradient terrain / low unit cost earthwork excavation estimates. The manual does not recommend that these data be used for final design, excavation and grading plans, earthwork computations for bid estimates or contract measurement and payment. This dataset does not take the place of an on-site survey for design, construction or regulatory purposes.

This dataset provides topographic indices derived from 1 m resolution DEMs for sequoia groves in both Sequoia-Kings Canyon and Yosemite National Parks. All mapped sequoia groves in Sequoia-Kings Canyon National Park and two groves from Yosemite National Park, Merced and Mariposa, are included. For each grove, aspect, slope, the stream network, height above nearest drainage (HAND), depth to water (DTW), maximum elevation deviation (DEVmax), and heat load index (HLI) are calculated. These indices were chosen because of their relevance in determining soil moisture across a landscape. Derived topographic parameters were calculated using 1 m DEMs generated in 2016 resampled to 3 m and a combination of ArcGIS Pro Tools, ArcPy Scripts, Whitebox GAT tools, and R scripts. The stream networks, which are further used in the calculation of HAND and DTW, were determined using a flow accumulation threshold of 2000 meters squared based on a literature-accepted range, chosen specifically based on knowledge of the areas of interest. The neighborhood size range for DEVmax was chosen on two scales, allowing for the identification of both local and more global minima and maxima: squares centered at each pixel ranging from 9 to 303 meters and 9 to 1203 meters wide. The neighborhood size chosen by the algorithm at each pixel maximizes the deviation from the average. Files that include the neighborhood size chosen are included for reference. All files are included as GeoTIFF files.

This Digital Elevation Model (DEM) of the Vietnamese part of the Mekong delta was interpolated using almost 20.000 elevation points derived from a national topographical map of 2014 (scale 1:200,000). The elevation data is vertically referenced to the Vietnam's geodetic Hon Dau datum, which has its elevation origin at mean sea level (MSL) of the Hon Dau tide gauge. The DEM was interpolated from the topographical elevation points using empirical Bayesian kriging employing empirical data transformation and an exponential model. Elevation points with elevations higher than +10m, located on elevated bedrock outcrops were excluded from the interpolation. Rivers and bedrock outcrops were clipped from the final DEM. For more details on the elevation data, the interpolation procedure and data processing steps, see the corresponding paper and supplementary information.File name: Topo_DEM_Mekong_delta_excl_rivers_and_bedrock.ascFile format: ASCI fileSpatial reference: WGS_1984_UTM_Zone_48NVertical reference datum: Hon Dau datum (Vietnamese)Grid cell size: 500 x 500 m

Note: This service is only for using online; full resolution downloads are not supported. To enable pop ups when opening this in a new web map, then click the ellipsis (three blue dots) under the layer name in the contents, and choose Enable Pop-up.Image service created from Digital Elevation Models (DEMs) derived from county-produced LiDAR covering Wisconsin. Elevation units are in feet. This service was last updated May 2023. It can be used in conjunction with its associated Index layer, DEM and Hillshade from LiDAR - Index, to determine flight years of source LiDAR and resolution of source DEMs. Also see the Index layer item details for detailed information about counties included in this service and in related services: DEM from LiDAR (Units in Meters) and Hillshade from LiDAR.Some areas display as data gaps (white artifacts) when the service is viewed at statewide scales but display normally when zoomed in to scales of approximately 1:1,000,000 or larger. We hope to address the no-data areas and small-scale data gaps in future updates to this service. The source DEMs have not been hydrologically conditioned. The Vertical Datum for the DEMs is NAVD88.WI DNR acknowledges the USDA Natural Resources Conservation Service, USGS, FEMA, the Southeastern WI Regional Planning Commission, and the individual counties listed in DEM and Hillshade from LiDAR - Index, for making source data available. For more information, visit https://dnr.wi.gov/feedback/ and choose Geographic Information Systems Data as the subject.

Abstract

This dataset and its metadata statement were supplied to the Bioregional Assessment Programme by a third party and are presented here as originally supplied:

MrVBF is a topographic index designed to identify areas of deposited material at a range of scales based on the observations that valley bottoms are low and flat relative to their surroundings and that large valley bottoms are flatter than smaller ones. Zero values indicate erosional terrain with values 1 and larger indicating progressively larger areas of deposition. There is some evidence that MrVBF values correlate with depth of deposited material.

The 3 second resolution product was generated from the 1 second MrVBF product and masked by the 3" water and ocean mask datasets.

Dataset History

Data quality

Lineage:

Source data

1. The 1 second MrVBF product

2. 3 second resolution SRTM water body and ocean mask datasets

MrVBF calculation

The MrVBF method is described in Gallant and Dowling (2003). It is based on slope and position in landscape (ranking within a 3- or 6-cell circular window) calculated from the original DEM and progressively generalised DEMs. The algorithm used to create this product is version 6g-a5, which is slightly different to that in the original paper.

Each value of MrVBF is associated with a particular scale and slope threshold. For each successive value the slope threshold halves and the scale triples. At each scale a location is considered erosional if it is high (ranked above the majority of the surrounding cells) or steep (slope greater than the threshold), and depositional otherwise. The largest value takes precedence at each location, so a value of zero indicates the site is considered to be erosional at all scales.

Value Threshold Resolution Interpretation

   slope (%)  (approx)

0 30 m Erosional

1 16 30 Small hillside deposit

2 8 30 Narrow valley floor

3 4 90

4 2 270 Valley floor

5 1 800 Extensive valley floor

6 0.5 2.4 km

7 0.25 7.2 km Depositional basin

8 0.125 22 km

9 0.0625 66 km Extensive depositional basin

The 3 second version of MrVBF was derived from the 1 second MrVBF using the median value in each 3 x 3 group of 1 second cells.

MrVBF has been used with topographic wetness index (TWI) to predict soil depths; see McKenzie, Gallant and Gregory (2003) for details.

Positional accuracy:

The horizontal positional error is the same as for the raw SRTM 1 second data, with 90% of tested locations within 7.2 m for Australia. See Rodriguez et al. (2006) for more information.

Attribute accuracy:

MrVBF is designed to represent the degree of deposition within a landscape dominated by colluvial and alluvial processes and the index has been found helpful for various purposes in much of Australia. There are several circumstances where it can be misleading:

* In areas dominated by aeolian transport the assumptions behind the method are not met, and dunes (for example) are represented as erosional features with MrVBF = 0.

* Alluvial and colluvial fans are depositional but stand above their surroundings so often appear as erosional features with MrVBF = 0.

The characteristics of the SRTM data from which DEM-S has been derived means that there are often small raised areas within otherwise flat landscapes that may be artefacts; MrVBF will often have a small value or 0 on those features.

Logical consistency:

This product is a consistent representation of terrain based on the information in DEM-S.

Completeness:

The MrVBF product covers the same area as the source DEM-S, which is virtually all of continental Australia and near coastal islands. Some tiles containing parts of mainland or pieces of islands were not supplied at 1 second resolution and are therefore missing, see DEM-S metadata for details.

Dataset Citation

CSIRO (2000) Multi-resolution Valley Bottom Flatness MrVBF at three second resolution CSIRO 20000211. Bioregional Assessment Source Dataset. Viewed 12 December 2018, http://data.bioregionalassessments.gov.au/dataset/7dfc93bb-62f3-40a1-8d39-0c0f27a83cb3.

The Australian Digital Elevation Model (DEM) has been developed using the CRES package ANUDEM. It is available at a continental scale at two spatial resolutions - 1/20th degree and 1/40th degree. The DEM is also available at a finer resolution (1/60th degree or 1 minute) for individual states.

The First DEM of Australia

The first DEM of Australia at a resolution of 1/10th degree (approximately 10 km) was calculated by Moore and Simpson (1982) using the minimum curvature interpolation procedure of Briggs (1974) applied to a point elevation data set containing about 320 000 points . These data were measured during a continent-wide gravity survey conducted by the Bureau of Mineral Resources (Anfiloff et al., 1976). Though detailed enough to detect significant geological structures (Harrington et al., 1982), this DEM suffered from a number of acknowledged limitations from the point of view of hydrological analysis. Extreme heights were not well represented and the 1/10th degree resolution could only support quite generalized drainage structures. The data were also known to contain a number of errors.

The New DEM of Australia

The new 1/40th degree DEM of Australia has been calculated by the elevation specific gridding technique described by Hutchinson (1988, 1989). This technique ensures that the DEM has a connected drainage structure by automatically removing spurious pits or sinks. The DEM also incorporates the stream line network digitized from the 1:2.5 M scale map of Australia (Division of National Mapping, 1984). A summary of the point elevation and stream line data used is given in Table I. A total of about 580 000 elevation data points were used, of which 400 000 were provided by the Bureau of Mineral Resources. These included the 320 000 elevation points used by Moore and Simpson (1982). The inclusion of the trigonometric data points ensured that most of the principal peaks were incorporated into the DEM. Additional point and stream line data were digitized from 1:250 000 scale topographic maps to provide more detail and to remove remaining drainage anomalies, particularly in areas with complex terrain. Sink data points were also digitized to prevent drainage clearance of genuine depressions, although the drainage enforcement algorithm is generally sufficiently sensitive to ensure that genuine depressions are not cleared, whether or not they have been identified as such in the data (Hutchinson, 1989).

[Summary provided by the Australian National University.]

Spatial coverage index compiled by East View Geospatial of set "Iceland 10M Digital Elevation Model". Source data from LI (publisher). Type: Elevation Database. Scale: 10m. Region: Europe.

Digital Elevation Model (DEM) for British Columbia produced by GeoBC. This data is the TRIM DEM converted to the Canadian Digital Elevation Data (CDED)format. The data consists of an ordered array of ground or reflective surface elevations, recorded in metres, at regularly spaced intervals. The spacing of the grid points is .75 arc seconds north/south. The data was converted into 1:50,000 grids for distribution. The scale of this modified data is 1:250,000 which was captured from the original source data which was at a scale of 1:20,000. The CDED format specification are available at ftp://ftp.geogratis.gc.ca/pub/nrcan_rncan/elevation/cdem_mnec/doc/CDEM_product_specs.pdf

Project Zone error threshold models. A point scale factor map with a 20PPM threshold applied. Generated using geodetic calculations and Digital Elevation Models (DEM) data.This data is used for road investigation, planning, design, construction and asset management.Data Dictionary: https://bit.ly/3glraQN

This is the 2nd release of the fourth version of an Everglades Depth Estimation Network (EDEN) digital elevation model (DEM) generated from certified airborne height finder (AHF) and airboat collected ground surface elevations for the Greater Everglades Region. Collectively, these data are referred to as "High Accuracy Elevation Data" (HAED). Inconsistencies in available greater Everglades boundary files resulted in a missing elevation value for 1 cell along the western boundary of WCA3s. In this release, that single cell was "filled" with a value of 2.19682 meters as determined through the kriging process summarized below. As was the case with the 1st release (EDEN_em_JA10), this version differs from the previous elevation model (EDEN_EM_OCT07) in several ways. First, the kriging algorithm applied to newly modeled subareas was changed from ordinary to universal kriging - resulting in slightly lower errors during cross-validation and accuracy assessment. Second, a previously omitted area in the northwestern corner of the Everglades National Park (ENP) and southern portion of Big Cypress National Preserve has been filled. Third, to increase accuracy in WCA1, the most challenging EDEN subarea from an elevation modeling standpoint, the Conservation area is subdivided into 4 zones (Northern, Central, Southwest and Southeast). Boundaries between the North, Central and two Southern zones is based upon landscape units defined through the CERP. The landscape unit representing approximately the southern third of WCA1 was further divided into two zones (east and west) based on marked changes in slope and aspect data generated from a DEM of the southern landscape unit as a whole. Division of WCA1 into 5 zones reduces errors estimated by comparing DEM modeled water depths with those measured by EDEN Principal Investigators in the field. Subdivision of the south landscape unit into east and west zones resulted in lower error estimates for the eastern subzone (i.e., southeast) without significantly affecting (i.e., improving or degrading) the quality of the western subzone - an area where DEM modeling is most challenging. Finally, to reduce artificial breaks in elevation along WCA1 subarea boundaries, models were overlapped by 1 cell at these boundaries and, for the North, Central and South zone boundaries, overlapping model values were averaged. For the boundaries between the Southwest and Southeast zones, cell values were "blended" based on weighted distance from the boundary edge. Finally, points along the North / Central and Central / South zone edges were subjectively selected and changed by adding or subtracting 0.03 meters (3 cm) to particular cells. This slightly reduces apparent artifacts without drastically affecting the integrity of the model. The EDEN offers a consistent and documented dataset that can be used to guide large-scale field operations, to integrate hydrologic and ecological responses, and to support biological and ecological assessments that measure ecosystem responses to Comprehensive Everglades Restoration Plan. To produce historic and near-real time maps of water depths, the EDEN requires a system-wide DEM of the ground surface.

This file is intended specifically for use in the EDEN applications software. Therefore, it is a modification of the EDEN DEM released in January of 2010 (i.e., eden_em_ja10). The released January 2010 data was modified by converting elevation values from meters (m) to centimeters (cm). In a previous release of this data set (eden_em_cm_ja10-notch) data was removed from the southern Big Cypress National Preserve and northwestern Everglades National Park area so that the DEM boundary matched the EDEN boundary. However, a new version of the EDEN water surface boundary has been released in October 2011, and provided for the release of eden_em_cm_ja10 which has the area of southern Big Cypress National Preserve and northwestern Everglades National Park filled in so that it now matchs the current water surface model in that area. Aside from this difference in units, the following data documentation applies.