|
|
Height Data
Accurate height information is a powerful tool in understanding the Earth’s surface and the built environment. By using height data in CAD and GIS systems you can build a clear 3D picture of a particular area and its natural and built environment. This can aid advanced site analysis, planning and modelling applications, as well as effective environmental analysis that is reliant on accurate flood risk and subsistence modelling.
Understanding Height Data
Digital Surface Models (DSM)
DSM's measure the height values of the first surface on the ground. This includes terrain features, buildings, vegetation and power lines etc. DSM’s therefore provide a topographic model of the earth's surface. DSM’s can be used to create 3D fly-throughs, support location-based systems and augmented simulated environments.
Digital Terrain Models (DTM)
DTM's provide a topographic model of the bare earth / underlying terrain of the earth's surface. They are usually derived from DSM's by digitally removing the cultural (man-made) and vegetation features described above.
Contours
Contours are the most popular and widely understood way of visualising and presenting height data. They are derived from the measured height values and are available in DXF and DWG formats for CAD or GIS. Generating contours involves a certain amount of approximation and the accuracy depends on the accuracy/density of the height values from which they are derived.
Where to find height data in Promap?
All height data can be purchased by locating to your site and selecting the Export Data options.
The range of height data available for that area will be displayed, select the one you require and the format type and proceed through the purchase options.
DTM
DTM's provide a topographic model of the bare earth / underlying terrain of the earth's surface. They are usually derived from DSM's by digitally removing the cultural (man-made) and vegetation features.
Where to find height data in Promap?
All height data can be purchased by locating to your site and selecting the Export Data options.
The range of height data available for that area will be displayed, select the one you require and the format type and proceed through the purchase options.
Sample Height Data
What is the difference between LiDAR, RADAR and Photogrammetrically derived height data?
LiDAR (Light Detection and Ranging)
LiDAR has revolutionised the acquisition of digital elevation data. There is no other method that can collect ground and surface height information as quickly and accurately. These factors make LiDAR a highly viable option for all applications that require height, volume or 3D visualisation information.
This technique measures distances using Lazer technology. It measures how long it takes for a light wave to travel, bounce off an object and come back. From this data a height value is then obtained.
LiDAR data can integrated with the majority of GIS and CAD systems.
RADAR (IFSAR - Interferometric Synthetic Aperture Radar)
This technique works on the same principle as LiDAR but uses radio waves instead of light waves. Radar bounces radio waves and the time delay between transmission of a pulse and detection of the reflected signal to determine the range of an object.
Photogrammetry
This is the practice of obtaining information, about physical objects, including height values, through the process of recording, measuring, and interpreting photographic images. Photogrammetry has been included within some LiDAR datasets as it can prove more reliable areas with rapid changes in terrain.
Topographical Survey
GPS survey and in the past, surveys levelled to the national benchmark network have been included in some datasets. However, due to the high cost of collecting data in this way, survey data has not been widely used to collect and produce commercially available datasets and is primarily used to verify other capture methods.
DTM LIDAR
LiDAR has revolutionised the acquisition of digital elevation data. There is no other method that can collect ground and surface height information as quickly and accurately. These factors make LiDAR a highly viable option for all applications that require height, volume or 3D visualisation information.
The Environment Agency 25cm, 50cm, 1m and 2m DTM LiDAR Height Data
The EA LIDAR data has an accuracy of +/-5cm to 15cm, with the spatial resolutions ranging from 25cm to 2 metres.
The dataset has been developed to show a 'bare earth' Digital Terrain Models (DTM). This data can be used in a range of GIS and CAD formats.
The elevation data produced is suitable for a range of environmental applications, including flood risk assessment.
ASCII 1m sample
Format options: ASCII
Applications
3D modelling to aid visualisation and provide real world interpretation of sites
Flooding analysis
Feasibility studies
Risk Assessments
Reporting
Line of sight analysis
Noise and wind modelling
Sample Height Data
DTM RADAR
This technique works on the same principle as LiDAR but uses radio waves instead of light waves. Radar bounces radio waves and the time delay between transmission of a pulse and detection of the reflected signal to determine the range of an object.
RADAR is also known as IFSAR (Interferometric Synthetic Aperture Radar)
NEXTMAP 5m DTM RADAR Height Data
Within the NEXTMAP height data elevation points are provided every five meters. For the DTM, the ground surface objects have been processed and removed to give a representation of the bare earth at an accuracy of +/- 1m.
DXF sample
XYZ sample
Format options: DWG, DXF, XYZ, ASCII
DSM
DSM's measure the height values of the first surface on the ground. This includes terrain features, buildings, vegetation and power lines etc. DSM’s therefore provide a topographic model of the earth's surface. DSM’s can be used to create 3D fly-throughs, support location-based systems and augmented simulated environments.
Where to find height data in Promap?
All height data can be purchased by locating to your site and selecting the Export Data options.
The range of height data available for that area will be displayed, select the one you require and the format type and proceed through the purchase options.
What is the difference between LiDAR, RADAR and Photogrammetrically derived height data?
LiDAR (Light Detection and Ranging)
LiDAR has revolutionised the acquisition of digital elevation data. There is no other method that can collect ground and surface height information as quickly and accurately. These factors make LiDAR a highly viable option for all applications that require height, volume or 3D visualisation information.
This technique measures distances using Lazer technology. It measures how long it takes for a light wave to travel, bounce off an object and come back. From this data a height value is then obtained.
LiDAR data can integrated with the majority of GIS and CAD systems.
RADAR (IFSAR - Interferometric Synthetic Aperture Radar)
This technique works on the same principle as LiDAR but uses radio waves instead of light waves. Radar bounces radio waves and the time delay between transmission of a pulse and detection of the reflected signal to determine the range of an object.
Photogrammetry
This is the practice of obtaining information, about physical objects, including height values, through the process of recording, measuring, and interpreting photographic images. Photogrammetry has been included within some LiDAR datasets as it can prove more reliable areas with rapid changes in terrain.
Topographical Survey
GPS survey and in the past, surveys levelled to the national benchmark network have been included in some datasets. However, due to the high cost of collecting data in this way, survey data has not been widely used to collect and produce commercially available datasets and is primarily used to verify other capture methods.
DSM LIDAR
LIDAR has revolutionised the acquisition of digital elevation data. There is no other method that can collect ground and surface height information as quickly and accurately. These factors make LiDAR a highly viable option for all applications that require height, volume or 3D visualisation information
The Environment Agency 25cm, 50cm, 1m and 2m DSM LIDAR Height Data
The EA LIDAR data has an accuracy of +/-5cm to 15cm, with the spatial resolutions ranging from 25cm to 2 metres.
The dataset has been developed to show the DSM (Digital Surface Model; where all surface objects are included). This data can be used in a range of GIS and CAD formats.
The elevation data produced is suitable for a range of environmental applications, including flood risk assessment.
ASCII 1m sample
Format options: ASCII
Applications
3D modelling to aid visualisation and provide real world interpretation of sites
Flooding analysis
Feasibility studies
Risk Assessments
Reporting
Line of sight analysis
Noise and wind modelling
DSM RADAR
This technique works on the same principle as LiDAR but uses radio waves instead of light waves. Radar bounces radio waves and the time delay between transmission of a pulse and detection of the reflected signal to determine the range of an object.
RADAR is also known as IFSAR (Interferometric Synthetic Aperture Radar)
NEXTMAP 5m DDM RADAR Height Data
Using airborne RADAR technology the ground surface has been modelled in a detail with elevation points provided every five meters. The measurements are derived from the return signals received that bounce off the first surface they strike, making the DSM a representation of any object large enough to be resolved. These include buildings, vegetation and roads, as well as natural terrain features at an accuracy of +/- 1.
DXF sample
XYZ sample
Format options: ASCII
Format options: DWG, DXF, XYZ, ASCII
Understanding Contour data collection methods
Photogrammetry
This is the practice of obtaining information, about physical objects, including height values, through the process of recording, measuring, and interpreting photographic images. Photogrammetry has been included within some LiDAR datasets as it can prove more reliable areas with rapid changes in terrain.
Topographical Survey
GPS survey and in the past, surveys levelled to the national benchmark network have been included in some datasets. However, due to the high cost of collecting data in this way, survey data has not been widely used to collect and produce commercially available datasets and is primarily used to verify other capture methods.
Applications
Terrain analysis
Drainage analysis
Visual impact studies
Site analysis
Contour data
OS Land-Form PROFILE Contours
Ordnance Survey's Land-Form PROFILE contour data is a data set representing the physical shape of the real world within Great Britain. Contained within this data set are height contours, and high and low water marks. Contour data has been captured from Ordnance Survey's 1:10 000 scale mapping.
DWG sample
OS Land-Form PANORAMA Contours
Like the OS PROFILE product (Ordnance Survey Land-Form PROFILE Contour Data), the OS PANORAMA product is a dataset representing the physical shape of the real world, and contains contour data. PANORAMA contour features are at 10 m elevation intervals (compared to 5m elevation intervals in the OS PROFILE product)
The accuracy of digital contours is typically better than 3 m (root mean square error (RMSE)). These refer to the differences between the contour height recorded on the map and the measured height (above mean sea level) at the points on the ground represented by that contour.
DXF sample
Format options: DWG, DXF
|
