Optionally, the capability to load and visualize sections of the survey data in 3D. These along and across path profiles are generated by cutting an accurate slice through the entire grid, and therefore, can be used to compute more accurate values of seabed distances and slacks than those computed using the conventional method of intersecting bathymetric contours.Īll maps can be automatically geo-referenced as Geotiffs and be viewable as layers on the main MakaiPlan GIS window. Superimpose the RPL on any of the created maps and quickly generate accurate slope graphs along and across any desired route section.
#Digital terrain model，dtm for free#
IHDTM data are available for free to users of the EDINA Environment Digimap service, which includes staff and students at more than a hundred UK further and higher education establishments.Create grid files using a variety of methodsĬreate contour colored maps (colors, numbers, and spacing of contour lines are user defined and maps can be directly loaded into the GIS database), which allow the user to visualize either water depths or the maximum seabed slopes.Ĭreate color shaded relief maps with user definable sun elevation and azimuth. It is an automatically generated Digital Terrain Model (DTM. WorldDEM DTMlite is an accurate Digital Terrain Model (DTM) on a Global Scale. Please fill in our form to request map data Academic research and education WorldDEM DTMlite is the global digital terrain model covering seamlessly and homogeneously the entire land surface of the Earth at an unrivaled resolution of 24 meters meeting high-quality standards. To obtain a licence, please contact the UKCEH Data Licensing Team by email or telephone, or by clicking the button below to fill in our data request form: NERC, Institute of Hydrology, Wallingford. Sub-set of UK 50m by 50m hydrological digital terrain model grids. Proc 4th International Symposium on Spatial Data Handling. IHDTM Surface TypeĬell values in Surface Type grid represent the most hydrologically significant surface type existing in the 50m square centred on the grid point, where the types rated in increasing order of significance are: land, river, lake, intertidal, sea. This grid was derived from the Outflow grid. IHDTM Cumulative Catchment AreaĬell values in the Cumulative Catchment Area grid represent the total number of cells that drain into that cell. The Inflow grid has been obtained directly from the Outflow data and is used in order to accelerate some applications, in particular catchment boundary definition. To improve the DTM, all the terrain points should be assigned to one of these point groups. Only the Ground and Road Surface groups are preserved in the DTM. If the point cloud classification is available, a terrain mask is computed based on the classified point groups. DSM, Orthomosaic and Index After processing step 3. This has been an iterative process and makes the IHDTM grids unique.įlow direction is provided by allocating a value to each cell that represents one of the surrounding eight cells into which water from that cell will flow. The Digital Terrain Model (DTM) can be generated: During processing step 3. For example, where there is no change of elevation between cells it might not be possible to determine the correct flow direction using automated algorithms. The Outflow grid has been modified from the raw output of flow direction algorithms to enforce the "correct" direction of flow based on other sources of knowledge aside from the adjacent eight cells in the Elevation grid itself. The Outflow grid was developed from the Elevation grid but with substantial modification to ensure hydrological consistency. Extensive work has been done to ensure that the hydrological behaviour that will be predicted by running models on this DTM correspond as far as possible with reality. This is a hydrologically consistent DTM providing height in units of 10cms. The IHDTM is comprised of five separate gridded datasets which can be licensed together or separately.Įlevation (height), Outflow and Inflow drainage directions, Cumulative Catchment Area and Surface Type.Įach IHDTM grid is hydrologically consistent with the other IHDTM grids and with the CEH 1:50,000 Watercourse Network dataset. This is a 50m grid interval digital terrain model (DTM) derived from 1:50,000 scale mapping from Ordnance Survey and Land & Property Services (previously OSNI).
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