The LIDAR Composite DTM (Digital Terrain Model) is a raster elevation model covering ~99% of England at 1m spatial resolution. The DTM (Digital Terrain Model) is produced from the last or only laser pulse returned to the sensor. We remove surface objects from the Digital Surface Model (DSM), using bespoke algorithms and manual editing of the data, to produce a terrain model of just the surface.

Produced by the Environment Agency in 2022, the DTM is derived from a combination of our Time Stamped archive and National LIDAR Programme surveys, which have been merged and re-sampled to give the best possible coverage. Where repeat surveys have been undertaken the newest, best resolution data is used. Where data was resampled a bilinear interpolation was used before being merged.

The 2022 LIDAR Composite contains surveys undertaken between 6th June 2000 and 2nd April 2022. Please refer to the metadata index catalgoues which show for any location which survey was used in the production of the LIDAR composite.

The data is available to download as GeoTiff rasters in 5km tiles aligned to the OS National grid. The data is presented in metres, referenced to Ordinance Survey Newlyn and using the OSTN’15 transformation method. All individual LIDAR surveys going into the production of the composite had a vertical accuracy of +/-15cm RMSE.

Nearshore areas within Long Island Sound are of great interest to the Connecticut and New York research and management communities because of their ecological, recreational, and commercial importance. However, although advances in multibeam echosounder technology permit the construction of detailed digital terrain models of seafloor topography within deeper waters, limitations inherent with collecting multibeam data make using this technology in shallower waters (<10-m deep) more difficult and expensive. These limitations have often resulted in gaps of no data between multibeam bathymetric datasets and the adjacent shoreline. To address this problem, complete-coverage multibeam bathymetry acquired offshore of New London and Niantic Bay, Connecticut, has been integrated with hydrographic LIDAR acquired along the nearshore. The result is a more continuous seafloor perspective and a much smaller gap between the digital bathymetric data and the shoreline. These datasets are provided as ESRI grid and GeoTIFF formats in order to facilitate access, compatibility, and utility.

Light Detection and Ranging (LiDAR) data was collected by The Geoinformation Group using LiDAR-equipped survey aircraft for the main urban conurbations of England and Wales (including London, Manchester, Birmingham, Liverpool, Newcastle, Edinburgh and Glasgow) as part of the Cities Revealed project, and made available through the Landmap service. The GeoInformation Group (TGG) has processed the data so that they are available as Digital Terrain Models (ground surface only) and Digital Surface/Elevation Models (the ground and all features on it), both geographic databases with height and surface measurement information in the form of regular grids with intervals of 1 or 2 m. In addition, some First Pass and Last Pass data are available. The First Pass data provides height values for the top of the canopy (i.e. buildings, trees etc.) while the Last Pulse data provides height values for the bottom of the canopy and provides information about the shape of the terrain. The data are available in img format. The Joint Information Systems Committee (JISC) funded Landmap service which ran from 2001 to July 2014 collected and hosted a large amount of earth observation data for the majority of the UK, part of which was elevation data. After removal of JISC funding in 2013, the Landmap service is no longer operational, with the data now held at the NEODC.

When using the data please also add the following copyright statement: Cities Revealed © The GeoInformation Group yyyy

Nearshore areas within Long Island Sound are of great interest to the Connecticut and New York research and management communities because of their ecological, recreational, and commercial importance. However, although advances in multibeam echosounder technology permit the construction of detailed digital terrain models of seafloor topography within deeper waters, limitations inherent with collecting multibeam data make using this technology in shallower waters (<10-m deep) more difficult and expensive. These limitations have often resulted in gaps of no data between multibeam bathymetric datasets and the adjacent shoreline. To address this problem, complete-coverage multibeam bathymetry acquired offshore of New London and Niantic Bay, Connecticut, has been integrated with hydrographic LIDAR acquired along the nearshore. The result is a more continuous seafloor perspective and a much smaller gap between the digital bathymetric data and the shoreline. These datasets are provided as ESRI grid and GeoTIFF formats in order to facilitate access, compatibility, and utility.

Nearshore areas within Long Island Sound are of great interest to the Connecticut and New York research and management communities because of their ecological, recreational, and commercial importance. However, although advances in multibeam echosounder technology permit the construction of detailed digital terrain models of seafloor topography within deeper waters, limitations inherent with collecting multibeam data make using this technology in shallower waters (<10-m deep) more difficult and expensive. These limitations have often resulted in gaps of no data between multibeam bathymetric datasets and the adjacent shoreline. To address this problem, complete-coverage multibeam bathymetry acquired offshore of New London and Niantic Bay, Connecticut, has been integrated with hydrographic LIDAR acquired along the nearshore. The result is a more continuous seafloor perspective and a much smaller gap between the digital bathymetric data and the shoreline. These datasets are provided as ESRI grid and GeoTIFF formats in order to facilitate access, compatibility, and utility.

Data are distances (in cm) to water measured by an experimental near-infrared lidar sensor in six different setups (2017–9). Laboratory tests conducted at Imperial College London include quantifying the effect of (i) distance, (ii) sensor inclination, (iii) turbidity/clarity of the water, and (iv) ambient temperature on measurement bias. Outdoor tests at three locations in London interrogated the effect of varying water surface roughness on the measurements. A dataset of high-frequency measurements is also included, from which the effects of sample autocorrelation were interrogated.

The USGS, in cooperation with NOAA and the Connecticut DEP, is producing detailed maps of the seafloor in Long Island Sound. The current phase of this cooperative research program is directed toward analyzing how bathymetric relief relates to the distribution of sedimentary environments and benthic communities. As part of this program, digital terrain models (DTMs) from bathymetry collected as part of NOAA's hydrographic charting activities are converted into ESRI raster grids and imagery (primarily of 2-m resolution), verified with bottom sampling and photography, and used to produce interpretations of seabed geology and hydrodynamic processes. Although each of the 18 completed surveys, ranging in area from 12 to 293 square kilometers, individually provides important benthic environmental information, many applications require a geographically broader perspective. For example, the usefulness of individual surveys is limited for the planning and construction of cross-Sound infrastructure, such as cables and pipelines, or for the testing of regional circulation models. To address this need, we integrated 12 multibeam and 2 LIDAR (Light Detection and Ranging) contiguous bathymetric DTMs into one dataset that covers much of eastern Long Island Sound. The new dataset is adjusted to mean lower low water, is provided in UTM Zone 18 NAD83 and geographic WGS84 projections, and is gridded to 4-m resolution. This resolution is adequate for seafloor-feature and process interpretation, but small enough to be queried and manipulated with standard GIS programs and to allow for future growth. Natural features visible in the grid include exposed bedrock outcrops, boulder lag deposits of submerged moraines, sand-wave fields, and scour depressions that reflect the strength of the oscillating tidal currents. Bedform asymmetry allows interpretations of net sediment transport. Anthropogenic artifacts visible in the bathymetric data include a dredged channel, shipwrecks, dredge spoils, mooring anchors, prop-scour depressions, buried cables, and bridge footings. Together the merged data reveal a larger, more continuous perspective of bathymetric topography than previously available, providing a fundamental framework for research and resource management activities in this major east-coast estuary.