MnTOPO is a web application for viewing, printing and downloading
high-resolution elevation data for the State of Minnesota that was collected using LiDAR technology. It runs on a variety of devices including desktop PCs, tablets, and mobile phones. The data you see and download in MnTOPO was made possible by the Minnesota elevation mapping project. MnTOPO is a collaborative effort between staff from the Minnesota
Information Technology (MN.IT) @ Minnesota Department of Natural Resources and MN.IT @ Minnesota Geospatial Information Office (MnGeo). Funding was provided by the Clean Water Fund of the Clean Water, Land and Legacy Amendment.

This viewer is available through CT ECO, a partnership between CT DEEP and UConn CLEAR. DescriptionThe Elevation Viewer contains statewide bare earth elevation. The elevation layers are pixels derived from a Lidar point cloud. The Hillshade, Shaded Relief, Slope, and Aspect are all part of the viewer and are different ways of viewing the bare earth elevation. The Viewer also contains contours, older elevation layers, and reference layers like parcels, aerial imagery, watersheds, and impervious surface. All about elevation on CT ECOLidar FAQ UseTo use the viewer, zoom in and then use the Layer List (upper right) to turn on and off layers (remember to turn OFF the ones above on the list or they will hide layers below) to compare and explore the area. The swipe tool (lower left) is a fun way to compare two datasets, especially aerial imagery with an elevation layer like hillshade or slope. Be sure at least two items are checked on in the layer list and use the swipe tool to compare. Refer to Viewer Help for more details and tips. Tipslidar points can reach the ground through tree canopy and exceptional at "seeing" features like stone walls that are not easily visible on aerial imagery"dynamic color" services means that the full range of colors is always displayed no matter what the viewing extentlidar points can also be used to create surfaces, which are different from bare earth elevation shown in the Elevation ViewerCT ECO has a 3D Lidar Point Viewer that contains points that have been colored based on summertime aerial imagery

This application shows LiDAR bare earth elevation layers from 2022 and 2018. Shaded relief views show the ground detail while popup windows display elevation in feet for the area clicked in the map.

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.

These data were created as part of the National Oceanic and Atmospheric Administration Office for Coastal Management's efforts to create an online mapping viewer called the Sea Level Rise and Coastal Flooding Impacts Viewer. It depicts potential sea level rise and its associated impacts on the nation's coastal areas. The purpose of the mapping viewer is to provide coastal managers and scientists with a preliminary look at sea level rise and coastal flooding impacts. The viewer is a screening-level tool that uses nationally consistent data sets and analyses. Data and maps provided can be used at several scales to help gauge trends and prioritize actions for different scenarios. The Sea Level Rise and Coastal Flooding Impacts Viewer may be accessed at: https://coast.noaa.gov/slr. This metadata record describes the Rhode Island digital elevation model (DEM), which is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea Level Rise and Coastal Flooding Impacts Viewer described above. This DEM includes the best available lidar known to exist at the time of DEM creation that met project specifications. This DEM includes data for the entire state. The DEM was produced from the following lidar data sets: 1. 2013 - 2014 USGS Hurricane Sandy Supplemental for NE (RI, MA, NH) 2. 2011 USGS ARRA Lidar for the Northeast: Rhode Island 3. 2010 FEMA Narragansett River Lidar The DEM is referenced vertically to the North American Vertical Datum of 1988 (NAVD88, Geoid12B) with vertical units of meters and horizontally to the North American Datum of 1983 (NAD83). The resolution of the DEM is approximately 3 meters.

There are a variety of resources available via The National Map homepage, such as static maps, interactive map viewers, and geospatial data. Some of these maps and apps include, the National Map Viewer, the 3D Elevation Program, the National Hydrography Dataset and Hydrography Viewer, the Historical Topographic Map and the US Topo. Via The National Map, historical topographic maps are available to search and download via a variety of options. The 3D Elevation Program (3DEP) provides information about, and access to elevation data meeting the 3DEP guidelines. Users can also access and view the National Hydrography Dataset via the Hydrography viewer; this is similar to the National Map Viewer, however the basemap is based on HUC watersheds. Using the National Map Viewer, users can search for, access and download current 7.5 minute US Topos for the entire country; users can also explore and view other data for their area of interest. Below, find links to the different The National Map resources that were described above. The National Map also provides access to other data and viewers, such as the National Land Cover Database, and The National Map Corps.

The U.S. Interagency Elevation Inventory (USIEI) displays high-accuracy topographic and bathymetric data for the United States and its territories. The project is a collaborative effort between the National Oceanic and Atmospheric Administration, the U.S. Geological Survey, the Federal Emergency Management Agency, the U.S. Department of Agriculture - Natural Resources Conservation Service and U.S. Forest Service, the National Park Service, and the U.S. Army Corps of Engineers. This resource is a comprehensive, nationwide listing of known high-accuracy topographic data, including lidar and IfSAR, and bathymetric data, including NOAA hydrographic surveys, multibeam data, and bathymetric lidar. This zip file contains the attribute information and footprints about the data sets that are displayed in the Topographic Lidar, Topobathy Shoreline Lidar, IfSAR Data, and Bathymetric Lidar layers in the USIEI viewer. This does not include the elevation data itself. The data are provided in Esri file geodatabase format (gdb) and in the open format of OGC GeoPackage (gpkg). The data is also available via this map service: https://coast.noaa.gov/arcgis/rest/services/USInteragencyElevationInventory/USIEIv2/MapServer. The data is updated quarterly. The information provided for each elevation data set includes many attributes such as vertical accuracy, point spacing, and date of collection. A direct link to access the data or information about the contact organization is also available through the inventory. The footprints in this data set are generalized to represent the coverage of the collection. If the exact data coverage is needed, please contact the data provider for an authoritative footprint. The fields in the gdb and gpkg are in four tables. The fields in each table are listed in the Entity Attribute Overview field.

The USGS Elevation Contours service from The National Map (TNM) consists of contours generated for the conterminous United States from 1- and 1/3 arc-second elevation data. Small scale contours derived from 1 arc-second data are displayed at scales ranging from 1:577K to 1:72K in The National Map viewer. Contour intervals are 100 foot between 1:577K and 1:144K, and 50 foot at 1:72K. Large scale contours derived from 1/3 arc-second data are displayed at 1:50K (and larger). Large scale contour intervals are variable across the United States depending on complexity of topography. The National Map viewer allows free downloads of public domain contour data in either Esri File Geodatabase or Shapefile formats. The 3D Elevation Program (3DEP) provides elevation data for The National Map and basic elevation information for earth science studies and mapping applications. Scientists and resource managers use elevation data for global change research, hydrologic modeling, resource monitoring, mapping and visualization, and many other applications. For additional information on 3DEP, go to http://nationalmap.gov/3DEP/.

This resource contains Lidar-DEM collection status shapefiles from the Texas Natural Resources Information System (TNRIS) [http://tnris.org]. November 2023 updates: this year, TNRIS changed its name to Texas Geographic Information Office (TxGIO). The domain name hasn't changed yet, but the data hub is continually evolving. See [1], [2] for current downloadable data.

For purposes of Hurricane Harvey studies, the 1-m DEM for Harris County (2008) has also been uploaded here as a set of 4 zipfiles containing the DEM in tiff files. See [1] for a link to the current elevation status map and downloadable DEMs.
Project name: H-GAC 2008 1m Datasets: 1m Point Cloud, 1M Hydro-Enforced DEM, 3D Breaklines, 1ft and 5ft Contours Points per sq meter: 1 Total area: 3678.56 sq miles Source: Houston-Galveston Area Council (H-GAC) Acquired by: Merrick, QA/QC: Merrick Catalog: houston-galveston-area-council-h-gac-2008-lidar

References: [1] TNRIS/TxGIO StratMap elevation data [https://tnris.org/stratmap/elevation-lidar/] [2] TNRIS/TxGIO DataHub [https://data.tnris.org/]

Source: https://carto.nationalmap.gov/arcgis/rest/services/contours/MapServerThe USGS Elevation Contours service from The National Map displays contours generated for the United States at various scales. Small-scale contours were created by USGS TNM from 1 arc-second data with 100-meter contours, and are visible at 1:600,000 and smaller scales. Medium-scale contours were created by USGS EROS from 1/3-arc-second data with 100-foot intervals, and are visible between 1:150,000 and 1:600,000. Additional medium-scale contours were created by USGS EROS from 1/3-arc-second data with 50-foot intervals, and are visible between 1:50,000 and 1:150,000. Large scale contours are updated every quarter, and are created by USGS TNM for the 7.5' 1:24,000-scale US Topo digital map series. These contours are derived from 1/3 arc-second or better resolution data, and are visible at scales 1:50,000 and larger. Large scale contour intervals are variable across the United States depending on complexity of topography, and as contours are generated per US Topo quadrangle, lines may not match across quad boundaries. The National Map download client allows free downloads of public domain contour data in either Esri File Geodatabase or Shapefile formats. The 3D Elevation Program (3DEP) provides elevation data for The National Map and basic elevation information for earth science studies and mapping applications. Scientists and resource managers use elevation data for global change research, hydrologic modeling, resource monitoring, mapping and visualization, and many other applications. For additional information on 3DEP, go to https://www.usgs.gov/3d-elevation-program. See https://apps.nationalmap.gov/help for assistance with The National Map viewer, download client, services, or metadata.

This is an image service providing access to bathymetric/topographic digital elevation models stewarded at NOAA's National Centers for Environmental Information (NCEI).There are 5 related image services providing access to Digital Elevation Models:DEM Mosaic (Individual DEMs)DEM Global Mosaic (Elevation Values)DEM Global Mosaic (Color Shaded Relief)CUDEM Mosaic (Elevation Values)CUDEM Mosaic (Color Shaded Relief)NCEI builds and distributes high-resolution, coastal digital elevation models (DEMs) that integrate ocean bathymetry and land topography to support NOAA's mission to understand and predict changes in Earth's environment, and conserve and manage coastal and marine resources to meet our Nation's economic, social, and environmental needs. They can be used for modeling of coastal processes (tsunami inundation, storm surge, sea-level rise, contaminant dispersal, etc.), ecosystems management and habitat research, coastal and marine spatial planning, and hazard mitigation and community preparedness. For more information about coastal DEMs at NCEI, please see: https://www.ncei.noaa.gov/products/coastal-elevation-models or learn more from our DEM Fact Sheet (1 MB PDF).This service provides data from many individual DEMs combined together as a mosaic (maximum of 80 rasters at once). By default, the rasters are drawn in order of cell size, with higher-resolution grids displayed on top of lower-resolution grids. If overlapping DEMs have the same resolution, the newer one is shown. Alternatively, a single DEM or group of DEMs can be isolated using a filter/definition query or using the "Lock Raster" mosaic method in ArcMap.The DEMs can be viewed in NCEI's Bathymetric Data Viewer along with other bathymetric datasets stewarded at NCEI.Please see NCEI's corresponding DEM Footprints map service for polygon footprints and more information about the individual DEMs used to create this composite view. The newer 1/3 and 1/9 arcsecond "tiled" DEMs are hosted by NOAA's Office for Coastal Management; please see the Data Access Viewer for access to these data. View these services together in a single combined map.This service has a server-side function available. This can be selected in the ArcGIS Online layer using "Image Display", or in ArcMap under "Processing Templates".None: The default. Provides elevation/depth values in meters. Please refer to the vertical datum for each DEM.ColorHillshade: An elevation-tinted hillshade visualization. The depths are displayed using this color ramp:THREDDS catalog (for extracting/downloading DEMs)

These data depict the elevation features of Konza Prairie. Record type 1 is a 2 meter resolution digital elevation model (DEM) of Konza Prairie, generated from 2006 LiDAR DEM data collected to standard USGS specifications (GIS200). Record type 3 is a 2010 10 meter (1/3 arc second) resolution National Elevation Dataset (NED) DEM of Konza Prairie (GIS202). Record type 4 is a 10 meter resolution NED DEM of Konza Prairie with a modified 3 kilometer buffer (GIS203). Record type 5 is a USGS topographic map of Konza Prairie (GIS204). These data are available as zipped (.zip) TIFF files (.tif). Data and metadata derived from DASC (record types 1 and 5), http://www.kansasgis.org/. Additional data and metadata derived from USGS (record types 3 and 4), http://www.nationalmap.gov/viewer.html.

These data were created as part of the National Oceanic and Atmospheric Administration Office for Coastal Management's efforts to create an online mapping viewer called the Sea Level Rise and Coastal Flooding Impacts Viewer. It depicts potential sea level rise and its associated impacts on the nation's coastal areas. The purpose of the mapping viewer is to provide coastal managers and scientist...

The TopoBathy 3D layer provides a global seamless topography (land elevation) and bathymetry (water depths) surface to use in ArcGIS 3D applications.What can you do with this layer?This layer is meant to be used as a ground in ArcGIS Online Web Scenes, ArcGIS Earth, and ArcGIS Pro to help visualize your maps and data in 3D.How do I use this layer?In the ArcGIS Online Web Scene Viewer:Sign-in with ArcGIS Online accountOn the Designer toolbar, click Add Layers Click Browse layers and choose Living Atlas.Search for TopoBathy 3DAdd TopoBathy 3D (Elevation Layer)The TopoBathy 3D will get added under Ground. Change basemap to OceansOptionally, add any other operational layers to visualize in 3DIn ArcGIS Pro:Ensure you are logged in with an ArcGIS Online accountOpen a Global SceneOn the Map tab, click Add Data > Elevation Source LayerUnder Portal, click Living Atlas and search for TopoBathy 3DSelect TopoBathy 3D (Elevation Layer) and click OKThe TopoBathy 3D will get added under GroundOptionally, remove other elevation layers from ground and choose the desired basemapDataset Coverage To see the coverage and sources of various datasets comprising this elevation layer, view the Elevation Coverage Map. Additionally, this layer uses data from Maxar’s Precision 3D Digital Terrain Models for parts of the globe.

The High Resolution Digital Elevation Model Mosaic provides a unique and continuous representation of the high resolution elevation data available across the country. The High Resolution Digital Elevation Model (HRDEM) product used is derived from airborne LiDAR data (mainly in the south) and satellite images in the north. The mosaic is available for both the Digital Terrain Model (DTM) and the Digital Surface Model (DSM) from web mapping services. It is part of the CanElevation Series created to support the National Elevation Data Strategy implemented by NRCan. This strategy aims to increase Canada's coverage of high-resolution elevation data and increase the accessibility of the products. Unlike the HRDEM product in the same series, which is distributed by acquisition project without integration between projects, the mosaic is created to provide a single, continuous representation of strategy data. The most recent datasets for a given territory are used to generate the mosaic. This mosaic is disseminated through the Data Cube Platform, implemented by NRCan using geospatial big data management technologies. These technologies enable the rapid and efficient visualization of high-resolution geospatial data and allow for the rapid generation of dynamically derived products. The mosaic is available from Web Map Services (WMS), Web Coverage Services (WCS) and SpatioTemporal Asset Catalog (STAC) collections. Accessible data includes the Digital Terrain Model (DTM), the Digital Surface Model (DSM) and derived products such as shaded relief and slope. The mosaic is referenced to the Canadian Height Reference System 2013 (CGVD2013) which is the reference standard for orthometric heights across Canada. Source data for HRDEM datasets used to create the mosaic is acquired through multiple projects with different partners. Collaboration is a key factor to the success of the National Elevation Strategy. Refer to the “Supporting Document” section to access the list of the different partners including links to their respective data.

This layer of the National Elevation Dataset (NED) is 1/9 arc-second (approximately 3 m) resolution. The 1/9 arc-second NED are derived from diverse source data that are processed to a common coordinate system and unit of vertical measure. These data are distributed in geographic coordinates in units of decimal degrees, and in conformance with the North American Datum of 1983 (NAD 83). All elevation values are in meters and, over the continental United States, are referenced to the North American Vertical Datum of 1988 (NAVD88). The 1/9 arc-second NED layer provides project-based coverage for portions of the conterminous United States, limited areas of Alaska, and Guam. The 1/9 arc-second NED layer is available as pre-staged products tiled in 15 minute blocks in Erdas .img format. The NED is updated continually as new data become available. For a quick reference to visualize where data exists for this collection see: http://viewer.nationalmap.gov/viewer/?p=ned. All NED data are in the public domain.

These data were created as part of the National Oceanic and Atmospheric Administration Office for Coastal Management's efforts to create an online mapping viewer called the NOAA Lake Level Viewer. It depicts potential lake level rise and fall and its associated impacts on the nation's coastal areas. The purpose of the mapping viewer is to provide coastal managers and scientists with a prelimina...

A national interactive map viewer with spatial information compiled by the USGS. US Topography, Geographic Names, Structures, Transportation, Governmental Unit Boundaries, Map Indices, Hydrology, Land Cover, Elevation, Elevation Contours, Imagery, Reference Polygons, Natural Hazards

Web map displaying Wisconsin DNR-produced Digital Elevation Model (DEM) and Hillshade image services, along with their index layer, in formats that are clickable and can be symbolized and filtered. This map can also be used as a starting point to create a new map. To open the web map from DNR's GIS Open Data Portal, click the View Metadata: link to the right of the description, then click Open in Map Viewer.

IntroductionClimate Central’s Surging Seas: Risk Zone map shows areas vulnerable to near-term flooding from different combinations of sea level rise, storm surge, tides, and tsunamis, or to permanent submersion by long-term sea level rise. Within the U.S., it incorporates the latest, high-resolution, high-accuracy lidar elevation data supplied by NOAA (exceptions: see Sources), displays points of interest, and contains layers displaying social vulnerability, population density, and property value. Outside the U.S., it utilizes satellite-based elevation data from NASA in some locations, and Climate Central’s more accurate CoastalDEM in others (see Methods and Qualifiers). It provides the ability to search by location name or postal code.The accompanying Risk Finder is an interactive data toolkit available for some countries that provides local projections and assessments of exposure to sea level rise and coastal flooding tabulated for many sub-national districts, down to cities and postal codes in the U.S. Exposure assessments always include land and population, and in the U.S. extend to over 100 demographic, economic, infrastructure and environmental variables using data drawn mainly from federal sources, including NOAA, USGS, FEMA, DOT, DOE, DOI, EPA, FCC and the Census.This web tool was highlighted at the launch of The White House's Climate Data Initiative in March 2014. Climate Central's original Surging Seas was featured on NBC, CBS, and PBS U.S. national news, the cover of The New York Times, in hundreds of other stories, and in testimony for the U.S. Senate. The Atlantic Cities named it the most important map of 2012. Both the Risk Zone map and the Risk Finder are grounded in peer-reviewed science.Back to topMethods and QualifiersThis map is based on analysis of digital elevation models mosaicked together for near-total coverage of the global coast. Details and sources for U.S. and international data are below. Elevations are transformed so they are expressed relative to local high tide lines (Mean Higher High Water, or MHHW). A simple elevation threshold-based “bathtub method” is then applied to determine areas below different water levels, relative to MHHW. Within the U.S., areas below the selected water level but apparently not connected to the ocean at that level are shown in a stippled green (as opposed to solid blue) on the map. Outside the U.S., due to data quality issues and data limitations, all areas below the selected level are shown as solid blue, unless separated from the ocean by a ridge at least 20 meters (66 feet) above MHHW, in which case they are shown as not affected (no blue).Areas using lidar-based elevation data: U.S. coastal states except AlaskaElevation data used for parts of this map within the U.S. come almost entirely from ~5-meter horizontal resolution digital elevation models curated and distributed by NOAA in its Coastal Lidar collection, derived from high-accuracy laser-rangefinding measurements. The same data are used in NOAA’s Sea Level Rise Viewer. (High-resolution elevation data for Louisiana, southeast Virginia, and limited other areas comes from the U.S. Geological Survey (USGS)). Areas using CoastalDEM™ elevation data: Antigua and Barbuda, Barbados, Corn Island (Nicaragua), Dominica, Dominican Republic, Grenada, Guyana, Haiti, Jamaica, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, San Blas (Panama), Suriname, The Bahamas, Trinidad and Tobago. CoastalDEM™ is a proprietary high-accuracy bare earth elevation dataset developed especially for low-lying coastal areas by Climate Central. Use our contact form to request more information.Warning for areas using other elevation data (all other areas)Areas of this map not listed above use elevation data on a roughly 90-meter horizontal resolution grid derived from NASA’s Shuttle Radar Topography Mission (SRTM). SRTM provides surface elevations, not bare earth elevations, causing it to commonly overestimate elevations, especially in areas with dense and tall buildings or vegetation. Therefore, the map under-portrays areas that could be submerged at each water level, and exposure is greater than shown (Kulp and Strauss, 2016). However, SRTM includes error in both directions, so some areas showing exposure may not be at risk.SRTM data do not cover latitudes farther north than 60 degrees or farther south than 56 degrees, meaning that sparsely populated parts of Arctic Circle nations are not mapped here, and may show visual artifacts.Areas of this map in Alaska use elevation data on a roughly 60-meter horizontal resolution grid supplied by the U.S. Geological Survey (USGS). This data is referenced to a vertical reference frame from 1929, based on historic sea levels, and with no established conversion to modern reference frames. The data also do not take into account subsequent land uplift and subsidence, widespread in the state. As a consequence, low confidence should be placed in Alaska map portions.Flood control structures (U.S.)Levees, walls, dams or other features may protect some areas, especially at lower elevations. Levees and other flood control structures are included in this map within but not outside of the U.S., due to poor and missing data. Within the U.S., data limitations, such as an incomplete inventory of levees, and a lack of levee height data, still make assessing protection difficult. For this map, levees are assumed high and strong enough for flood protection. However, it is important to note that only 8% of monitored levees in the U.S. are rated in “Acceptable” condition (ASCE). Also note that the map implicitly includes unmapped levees and their heights, if broad enough to be effectively captured directly by the elevation data.For more information on how Surging Seas incorporates levees and elevation data in Louisiana, view our Louisiana levees and DEMs methods PDF. For more information on how Surging Seas incorporates dams in Massachusetts, view the Surging Seas column of the web tools comparison matrix for Massachusetts.ErrorErrors or omissions in elevation or levee data may lead to areas being misclassified. Furthermore, this analysis does not account for future erosion, marsh migration, or construction. As is general best practice, local detail should be verified with a site visit. Sites located in zones below a given water level may or may not be subject to flooding at that level, and sites shown as isolated may or may not be be so. Areas may be connected to water via porous bedrock geology, and also may also be connected via channels, holes, or passages for drainage that the elevation data fails to or cannot pick up. In addition, sea level rise may cause problems even in isolated low zones during rainstorms by inhibiting drainage.ConnectivityAt any water height, there will be isolated, low-lying areas whose elevation falls below the water level, but are protected from coastal flooding by either man-made flood control structures (such as levees), or the natural topography of the surrounding land. In areas using lidar-based elevation data or CoastalDEM (see above), elevation data is accurate enough that non-connected areas can be clearly identified and treated separately in analysis (these areas are colored green on the map). In the U.S., levee data are complete enough to factor levees into determining connectivity as well.However, in other areas, elevation data is much less accurate, and noisy error often produces “speckled” artifacts in the flood maps, commonly in areas that should show complete inundation. Removing non-connected areas in these places could greatly underestimate the potential for flood exposure. For this reason, in these regions, the only areas removed from the map and excluded from analysis are separated from the ocean by a ridge of at least 20 meters (66 feet) above the local high tide line, according to the data, so coastal flooding would almost certainly be impossible (e.g., the Caspian Sea region).Back to topData LayersWater Level | Projections | Legend | Social Vulnerability | Population | Ethnicity | Income | Property | LandmarksWater LevelWater level means feet or meters above the local high tide line (“Mean Higher High Water”) instead of standard elevation. Methods described above explain how each map is generated based on a selected water level. Water can reach different levels in different time frames through combinations of sea level rise, tide and storm surge. Tide gauges shown on the map show related projections (see just below).The highest water levels on this map (10, 20 and 30 meters) provide reference points for possible flood risk from tsunamis, in regions prone to them.