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.

PLEASE NOTE: This dataset has been retired. A new version of the data is available here: https://environment.data.gov.uk/dataset/09ea3b37-df3a-4e8b-ac69-fb0842227b04 The LIDAR Composite DTM (Digital Terrain Model) is a raster elevation model covering >93% of England at 2m spatial resolution. Produced by the Environment Agency in 2020, this dataset is derived from a combination of our Time Stamped archive and National LIDAR Programme, which has 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 2020 LIDAR Composite contains surveys undertaken between 6th June 2000 and 1st September 2020. Please refer to the survey index files which shows, for any location, what Time Stamped survey or National LIDAR Programme block went into the production of the LIDAR composite for a specific location. The DTM (Digital Terrain Model) is produced from the last return LIDAR signal. 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. Available to download as GeoTiff files in 5km grids, data is presented in metres, referenced to Ordinance Survey Newlyn, using the OSTN’15 transformation. All LIDAR data has a vertical accuracy of +/-15cm RMSE. Light Detection and Ranging (LIDAR) is an airborne mapping technique, which uses a laser to measure the distance between the aircraft and the ground. Up to 500,000 measurements per second are made of the ground, allowing highly detailed terrain models to be generated at spatial resolutions of between 25cm and 2 metres. The Environment Agency’s open data LIDAR archives includes the Point Cloud data, and derived raster surface models of survey specific areas dating back to 1998 and composites of the best data available in any location. This metadata record is for Approval for Access product AfA458. Attribution statement: (c) Environment Agency copyright and/or database right 2021. All rights reserved. Attribution Statement: © Environment Agency copyright and/or database right 2015. All rights reserved.

Zoom in on the map above and click your area of interest or use the Tile Index linked below to determine which package(s) you require for download.The DTM data is available in the form of 1-km by 1-km non-overlapping tiles grouped into packages for download.This dataset is a compilation of lidar data from multiple acquisition projects, as such specifications, parameters and sensors may vary by project. See the detailed User Guide linked below for additional information.You can monitor the availability and status of lidar projects on the Ontario Lidar Coverage map on the Ontario Elevation Mapping Program hub page. Now also available through a web service which exposes the data for visualization, geoprocessing and limited download. The service is best accessed through the ArcGIS REST API, either directly or by setting up an ArcGIS server connection using the REST endpoint URL. The service draws using the Web Mercator projection. For more information on what functionality is available and how to work with the service, read the Ontario Web Raster Services User Guide. If you have questions about how to use the service, email Geospatial Ontario (GEO) at geospatial@ontario.ca.Service Endpointshttps://ws.geoservices.lrc.gov.on.ca/arcgis5/rest/services/Elevation/Ontario_DTM_LidarDerived/ImageServerhttps://intra.ws.geoservices.lrc.gov.on.ca/arcgis5/rest/services/Elevation/Ontario_DTM_LidarDerived/ImageServer (Government of Ontario Internal Users)Additional Documentation Ontario DTM (Lidar-Derived) - User Guide (DOCX) OMAFRA Lidar 2016-2018 - Cochrane - Additional Contractor Metadata (PDF)OMAFRA Lidar 2016-2018 - Peterborough - Additional Contractor Metadata (PDF)OMAFRA Lidar 2016-2018 - Lake Erie - Additional Contractor Metadata (PDF)CLOCA Lidar 2018 - Additional Contractor Metadata (PDF)South Nation Lidar 2018-19 - Additional Contractor Metadata (PDF)OMAFRA Lidar 2022 - Lake Huron - Additional Contractor Metadata (PDF)OMAFRA Lidar 2022 - Lake Simcoe - Additional Contractor Metadata (PDF)Huron-Georgian Lidar 2022-23 - Additional Contractor Metadata (Word)Kawartha Lakes Lidar 2023 - Additional Contractor Metadata (Word)Sault Ste Marie Lidar 2023-24 - Additional Contractor Metadata (Word)Thunder Bay Lidar 2023-24 - Additional Contractor Metadata (Word)Timmins Lidar 2024 - Additional Contractor Metadata (Word)Cataraqui Lidar 2024 - Additional Metadata (Word)Chapleau Lidar 2024 - Additional Metadata (Word)Dryden-Ignace-Sioux Lookout Lidar 2024 - Additional Metadata (Word)Atikokan Lidar 2024 - Additional Metadata (Word) Ontario DTM (Lidar-Derived) - Tile Index (SHP)Ontario Lidar Project Extents (SHP) OMAFRA Lidar DTM 2016-2018 - Cochrane - Breaklines (SHP)OMAFRA Lidar DTM 2016-2018 - Peterborough - Breaklines (SHP)OMAFRA Lidar DTM 2016-2018 - Lake Erie - Breaklines (SHP)CLOCA Lidar DTM 2018 - Breaklines (SHP)South Nation Lidar DTM 2018-19 - Breaklines (SHP)Ottawa-Gatineau Lidar DTM 2019-20 - Breaklines (SHP)OMAFRA Lidar DTM 2022 - Lake Huron - Breaklines (SHP)OMAFRA Lidar DTM 2022 - Lake Simcoe - Breaklines (SHP)Eastern Ontario Lidar DTM 2021-22 - Breaklines (SHP)Muskoka Lidar DTM 2018 - Breaklines CGVD2013 (SHP) / CGVD28 (SHP)Muskoka Lidar DTM 2021 - Breaklines CGVD2013 (SHP) / CGVD28 (SHP)Muskoka Lidar DTM 2023 - Breaklines CGVD2013 (SHP) / CGVD28 (SHP)DEDSFM Huron-Georgian Bay 2022-23 - Breaklines (SHP)DEDSFM Kawartha Lakes 2023 - Breaklines (SHP)DEDSFM Sault Ste Marie 2023-24- UTM16 - Breaklines (SHP)DEDSFM Sault Ste Marie 2023-24- UTM17 - Breaklines (SHP)DEDSFM Sudbury 2023-24 - Breaklines (SHP)DEDSFM Thunder Bay 2023-24 - Breaklines (SHP)DEDSFM Timmins 2024 - Breaklines (SHP)DEDSFM Cataraqui 2024 - Breaklines (SHP)DEDSFM Chapleau 2024 - Breaklines (SHP)DEDSFM Dryden 2024 - Breaklines (SHP)DEDSFM Ignace 2024 - Breaklines (SHP)DEDSFM Sioux Lookout 2024 - Breaklines (SHP)DEDSFM Northeastern Ontario 2024 - Breaklines (SHP)DEDSFM Atikokan 2024 - Breaklines (SHP)Product PackagesDownload links for the Ontario DTM (Lidar-Derived) (Word)Projects:LEAP 2009GTA 2014-18OMAFRA 2016-18CLOCA 2018South Nation CA 2018-19Muskoka 2018-23York-Lake Simcoe 2019Ottawa River 2019-20Ottawa-Gatineau 2019-20Lake Nipissing 2020Hamilton-Niagara 2021Huron Shores 2021Eastern Ontario 2021-22OMAFRA Lake Huron 2022OMAFRA Lake Simcoe 2022Belleville 2022Digital Elevation Data to Support Flood Mapping 2022-26Huron-Georgian Bay 2022-23Kawartha Lakes 2023Sault Ste Marie 2023-24Sudbury 2023-24Thunder Bay 2023-24Timmins 2024Cataraqui 2024Chapleau 2024Dryden 2024Ignace 2024Northeastern Ontario 2024Sioux Lookout 2024Atikokan 2024Greater Toronto Area Lidar 2023StatusOn going: Data is continually being updatedMaintenance and Update FrequencyAs needed: Data is updated as deemed necessaryContactOntario Ministry of Natural Resources - Geospatial Ontario, geospatial@ontario.ca

This dataset is retired and no longer available on the Data Services Platform. The Environment Agency Geomatics team no longer produce a 25cm resolution composite product. This has been replaced by a 1m resolution version. The entire archive of lidar data, including the 1m composite and 25cm time-stamped data, is available to download from the following page: https://environment.data.gov.uk/survey. The LIDAR Composite DTM (Digital Terrain Model) is a raster elevation model covering areas of England at 25cm spatial resolution. Produced by the Environment Agency in 2017, this dataset is derived from a combination of our full time stamped archive, which has been merged and re-sampled to give the best possible coverage. Where repeat surveys have been undertaken the newest, best resolution data is used. The composite is updated on an annual basis to include the latest surveys. The DTM (Digital Terrain Model) is produced from the last return LIDAR signal. 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. Available to download as ASCII files in 5km grids, data is presented in metres, referenced to Ordinance Survey Newlyn, using the OSTN’15 transformation. All LIDAR data has a vertical accuracy of +/-15cm RMSE. A tinted shaded relief, which is an image showing what LIDAR looks like when loaded into specialist software, is also available as a WMS feed. You can also download survey index files which shows, for any location, what Time Stamped survey went into the production of the LIDAR composite. Light Detection and Ranging (LIDAR) is an airborne mapping technique, which uses a laser to measure the distance between the aircraft and the ground. Up to 500,000 measurements per second are made of the ground, allowing highly detailed terrain models to be generated at spatial resolutions of between 25cm and 2 metres. The Environment Agency’s open data LIDAR archives includes the Point Cloud data, and derived raster surface models of survey specific areas and composites of the best data available in any location. To find out more about LIDAR and the various surface models we produce please read our story map

Bare earth elevation surface (DTM) and actual surface (DSM) given in meters in the NAVD88 (Geoid12A realization) vertical reference frame. Horizontal coordinates referenced to appropriate UTM zone. Bare earth is created by classifying and removing vegetation and man-made structures from lidar point cloud prior to surface generation. Both the DSM and DTM are mosaicked onto a spatially uniform grid at 1 m spatial resolution in 1 km by 1 km tiles provided in a geotiff format.

The LIDAR DTM (Digital Terrain Model) Time Stamped Tiles product is an archive of raster elevation data produced by the Environment Agency. Site specific LIDAR surveys have been carried out across England since 1998, with certain areas, such as the coastal zone, being surveyed multiple times. Data is available at varying resolutions of 25cm, 50cm, 1m and 2m, depending on project requirements.

The DTM (Digital Terrain Model) is produced from the last return LIDAR signal. 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.

Available to download as GeoTiff rasters in 5km zipfiles, data is presented in metres, referenced to Ordnance Survey Newlyn and data aligned to the OS Grid. All LIDAR data has a vertical accuracy of +/-15cm RMSE. The transformation used on the data is specific to the time period of survey.

Please refer to the metadata index catalogue which show, for any location, what time stamped data is available, the specific dates of survey, resolution of product and what transformation and geoidal model used.

This dataset shows the extent of data in each individual tile that went into the merging process to create the LIDAR Composite DSM & DTM.

Light Detection and Ranging (LIDAR) is an airborne mapping technique, which uses a laser to measure the distance between the aircraft and the ground. Up to 100,000 measurements per second are made of the ground, allowing highly detailed terrain models to be generated at spatial resolutions of between 25cm and 2 metres.

The Natural Resources Wales composite dataset contains digital elevation data derived from surveys carried out over several years and covers approximately 70% of Wales. We have made available 25cm, 50cm, 1m and 2m datasets, supplied as terrain models (a representation of the ground level) or surface models (a representation of object heights such as vehicles, buildings and vegetation).

In addition to the height information, georeferenced, coloured, shaded relief images at the same resolution as the input LiDAR data grids are available.

The LIDAR Composite DTM (Digital Terrain Model) is a raster elevation model covering ~99% of England at 2m 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. Attribution statement: © Environment Agency copyright and/or database right 2022. All rights reserved.

This dataset is Lidar data that has been collected by the Scottish public sector and made available under the Open Government Licence. The data are available as point cloud (LAS format or in LAZ compressed format), along with the derived Digital Terrain Model (DTM) and Digital Surface Model (DSM) products as Cloud optimized GeoTIFFs (COG) or standard GeoTIFF. The dataset contains multiple subsets of data which were each commissioned and flown in response to different organisational requirements. The details of each can be found at https://remotesensingdata.gov.scot/data#/list

This is a high resolution spatial dataset of Digital Terrain Model (DTM) data in South West England. The DTM along with a Digital Surface Model (DSM) cover an area of 9424 km2 that includes all the land west of Exmouth (i.e. west of circa 3 degrees 21 minutes West). The DTM represents the topographic model (height) of the bare earth. The dataset is a part of outcomes from the Centre for Ecology & Hydrology South West (SW) Project. There is also a Digital Surface Model (DSM) dataset covering the same areas available from the SW project.

PLEASE NOTE: This dataset has been retired. A new version of the data is available here: https://environment.data.gov.uk/dataset/09ea3b37-df3a-4e8b-ac69-fb0842227b04

The LIDAR Composite DTM (Digital Terrain Model) is a raster elevation model covering >93% of England at 2m spatial resolution.

Produced by the Environment Agency in 2020, this dataset is derived from a combination of our Time Stamped archive and National LIDAR Programme, which has 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 2020 LIDAR Composite contains surveys undertaken between 6th June 2000 and 1st September 2020. Please refer to the survey index files which shows, for any location, what Time Stamped survey or National LIDAR Programme block went into the production of the LIDAR composite for a specific location.

The DTM (Digital Terrain Model) is produced from the last return LIDAR signal. 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. Available to download as GeoTiff files in 5km grids, data is presented in metres, referenced to Ordinance Survey Newlyn, using the OSTN’15 transformation. All LIDAR data has a vertical accuracy of +/-15cm RMSE.

Light Detection and Ranging (LIDAR) is an airborne mapping technique, which uses a laser to measure the distance between the aircraft and the ground. Up to 500,000 measurements per second are made of the ground, allowing highly detailed terrain models to be generated at spatial resolutions of between 25cm and 2 metres. The Environment Agency’s open data LIDAR archives includes the Point Cloud data, and derived raster surface models of survey specific areas dating back to 1998 and composites of the best data available in any location.

This metadata record is for Approval for Access product AfA458.

Attribution statement: (c) Environment Agency copyright and/or database right 2021. All rights reserved. Attribution Statement: © Environment Agency copyright and/or database right 2015. All rights reserved.

This data was collected by the Geological Survey Ireland, the Department of Culture, Heritage and the Gaeltacht, the Discovery Programme, the Heritage Council, Transport Infrastructure Ireland, New York University, the Office of Public Works and Westmeath County Council. All data formats are provided as GeoTIFF rasters but are at different resolutions. Data resolution varies depending on survey requirements. Resolutions for each organisation are as follows: GSI – 1m DCHG/DP/HC - 0.13m, 0.14m, 1m NY – 1m TII – 2m OPW – 2m WMCC - 0.25m Both a DTM and DSM are raster data. Raster data is another name for gridded data. Raster data stores information in pixels (grid cells). Each raster grid makes up a matrix of cells (or pixels) organised into rows and columns. The grid cell size varies depending on the organisation that collected it. GSI data has a grid cell size of 1 meter by 1 meter. This means that each cell (pixel) represents an area of 1 meter squared. .hidden { display: none }

LiDAR (Light Detection and Ranging) is a remote sensing technology, i.e. the technology is not in direct contact with what is being measured. From satellite, aeroplane or helicopter, a LiDAR system sends a light pulse to the ground. This pulse hits the ground and returns back to a sensor on the system. The time is recorded to measure how long it takes for this light to return. Knowing this time measurement scientists are able to create topography maps.LiDAR data are collected as points (X,Y,Z (x & y coordinates) and z (height)). The data is then converted into gridded (GeoTIFF) data to create a Digital Terrain Model and Digital Surface Model of the earth. This LiDAR data was collected between June and October 2018.An ordnance datum (OD) is a vertical datum used as the basis for deriving heights on maps. This data is referenced to the Malin Head Vertical Datum which is the mean sea level of the tide gauge at Malin Head, County Donegal. It was adopted as the national datum in 1970 from readings taken between 1960 and 1969 and all heights on national grid maps are measured above this datum. Digital Terrain Models (DTM) are bare earth models (no trees or buildings) of the Earth’s surface.Digital Surface Models (DSM) are earth models in its current state. For example, a DSM includes elevations from buildings, tree canopy, electrical power lines and other features.Hillshading is a method which gives a 3D appearance to the terrain. It shows the shape of hills and mountains using shading (levels of grey) on a map, by the use of graded shadows that would be cast by high ground if light was shining from a chosen direction.This data shows the hillshade of the DTM.This data was collected by BlueSky and GeoAeroSpace and provided to the Geological Survey Ireland. All data formats are provided as GeoTIFF rasters but are at different resolutions. Data resolution is 1m.Both a DTM and DSM are raster data. Raster data is another name for gridded data. Raster data stores information in pixels (grid cells). Each raster grid makes up a matrix of cells (or pixels) organised into rows and columns. This data has a grid cell size of 1 meter by 1 meter. This means that each cell (pixel) represents an area of 1 meter squared.

Digital terrain model (DTM) with 1 metre ground resolution resulting from LiDAR scanning on an aerial platform acquired by the Ministry of the Environment and the Tuela del Territorio and del Mare as part of the Extraordinary Environmental Remote Sensing Plan. The survey concerned the I and II order river auctions (hierarchical order in the catalogue of IGM rivers).

The Ontario Lidar Digital Terrain Model (DTM) Geospatial Ontario (GEO) Dataset is a raster product representing the bare-earth terrain derived from a classified lidar point cloud. The DTM data is available in the form of 1-km by 1-km non-overlapping tiles grouped into packages for download. This dataset is a compilation of lidar data from multiple acquisition projects, as such specifications, parameters and sensors may vary by project. This data is for geospatial tech specialists, and is used by government, municipalities, conservation authorities and the private sector for land use planning and environmental analysis.

This data is no longer available on the Defra Data Services Platform. Visit Scottish Remote Sensing Portal to access the latest LIDAR data for Scotland: https://remotesensingdata.gov.scot/data#/list This metadata record is for Approval for Access product AfA458. Light Detection and Ranging (LIDAR) is an airborne mapping technique, which uses a laser to measure the distance between the aircraft and the ground. Up to 100,000 measurements per second are made of the ground, allowing highly detailed terrain models to be generated at spatial resolutions of between 25cm and 2 metres. The Environment Agency’s LIDAR data archive contains digital elevation data derived from surveys carried out by the Environment Agency's specialist remote sensing team. This dataset is derived from a combination of our full dataset which has been merged and re-sampled to give the best possible coverage. Data is available at 2m, 1m, 50cm, and 25cm resolution. The dataset can be supplied as a Digital Surface Model produced from the signal returned to the LIDAR (which includes heights of objects, such as vehicles, buildings and vegetation, as well as the terrain surface) or as a Digital Terrain Model produced by removing objects from the Digital Surface Model. The dataset can be presented as an ESRI Binary Grid which contains height values, or as a georeferenced JPEG which is an image showing what LIDAR looks like when loaded into specialist software. Attribution statement: Visit Scottish Remote Sensing Portal for information.

This dataset is no longer available on the Data Services Platform. New version of the LIDAR Composite DSM data is available here: https://environment.data.gov.uk/searchresults;query=lidar%20composite%202020;searchtype=All;page=1;pagesize=20;orderby=Relevancy The LIDAR Composite DTM (Digital Terrain Model) is a raster elevation model covering >60% of England at 1m spatial resolution. Produced by the Environment Agency in 2017, this dataset is derived from a combination of our full time stamped archive, which has been merged and re-sampled to give the best possible coverage. Where repeat surveys have been undertaken the newest, best resolution data is used. The composite is updated on an annual basis to include the latest surveys. The DTM (Digital Terrain Model) is produced from the last return LIDAR signal. 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. Available to download as ASCII files in 5km grids, data is presented in metres, referenced to Ordinance Survey Newlyn, using the OSTN’15 transformation. All LIDAR data has a vertical accuracy of +/-15cm RMSE. A tinted shaded relief, which is an image showing what LIDAR looks like when loaded into specialist software, is also available as a WMS feed. You can also download survey index files which shows, for any location, what Time Stamped survey went into the production of the LIDAR composite. Light Detection and Ranging (LIDAR) is an airborne mapping technique, which uses a laser to measure the distance between the aircraft and the ground. Up to 500,000 measurements per second are made of the ground, allowing highly detailed terrain models to be generated at spatial resolutions of between 25cm and 2 metres. The Environment Agency’s open data LIDAR archives includes the Point Cloud data, and derived raster surface models of survey specific areas and composites of the best data available in any location. To find out more about LIDAR and the various surface models we produce please read our story map This metadata record is for Approval for Access product AfA458. Attribution statement: (c) Environment Agency copyright and/or database right 2019. All rights reserved. Attribution Statement: © Environment Agency copyright and/or database right 2019 All rights reserved.

SpatioTemporal Asset Catalog (STAC) Item - warrick-dtm in indiana-lidar-dtm

This metadata record is for Approval for Access product AfA458. Light Detection and Ranging (LIDAR) is an airborne mapping technique, which uses a laser to measure the distance between the aircraft and the ground. Up to 100,000 measurements per second are made of the ground, allowing highly detailed terrain models to be generated at spatial resolutions of between 25cm and 2 metres. The Environment Agency’s LIDAR data archive contains digital elevation data derived from surveys carried out by the Environment Agency's specialist remote sensing team. This dataset is derived from a combination of our full dataset which has been merged and re-sampled to give the best possible coverage. Data is available at 2m, 1m, 50cm, and 25cm resolution. The dataset can be supplied as a Digital Surface Model produced from the signal returned to the LIDAR (which includes heights of objects, such as vehicles, buildings and vegetation, as well as the terrain surface) or as a Digital Terrain Model produced by removing objects from the Digital Surface Model. The dataset can be presented as an ESRI Binary Grid which contains height values, or as a georeferenced JPEG which is an image showing what LIDAR looks like when loaded into specialist software. Attribution statement: © Environment Agency copyright and/or database right 2016. All rights reserved.

Digital Terrain Model (DTM) for portions of the Hawaiian islands based upon lidar data collected by State of Hawaii and its data partners from 1999-2017. The DTM is a representation of "bare earth." The DTM is processed to digitally remove all surface objects including vegetation, leaving only the "bare earth," or underlying terrain. Elevation values are in meters.