A dataset is a collection of data that has been organized for a specific purpose. A dataset may be created for a specific research project, or it may be created as part of a larger data collection effort.
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Category: Location
A datum is a specific piece of information that is used as the basis for a measurement or calculation. A datum can be a physical object, such as a benchmark or a control point, or it can be a theoretical construct, such as a reference ellipsoid or a geoid.
James is the head of marketing at Tamoco
A platform that helps businesses buy advertising space on websites and other digital platforms.
James is the head of marketing at Tamoco
Depth is a measure of the vertical distance between two points. In the context of data, depth may refer to the number of layers in a data set, the number of levels in a hierarchy, or the number of dimensions in a data set.
James is the head of marketing at Tamoco
Information that can be used to identify a particular device, such as an IP address or a MAC address.
James is the head of marketing at Tamoco
An industry self-regulatory body that develops and enforces standards for online advertising.
James is the head of marketing at Tamoco
A digital elevation model (DEM) is a raster dataset in which every cell holds an elevation value, representing the height of the Earth’s surface across an area. It is the general term for digital height data, and in practice is used as an umbrella covering both the digital surface model (DSM) and the digital terrain model (DTM).
DEM, DSM and DTM are not interchangeable
This is the most common source of confusion in elevation data, and choosing the wrong one produces quietly wrong answers.
- DSM — includes everything on the surface: buildings, tree canopy, infrastructure.
- DTM — bare earth, with those objects removed.
- DEM — the generic term, which may mean either depending on the provider.
Because DEM is ambiguous, always check which the supplier actually means before using it.
How DEMs are produced
Common sources are LiDAR, photogrammetry from aerial or satellite imagery, and radar interferometry. Each carries different vertical accuracy and resolution, and the cell size of the raster sets the finest detail the model can express.
What they are used for
Elevation data supports flood and drainage modelling, line-of-sight and telecoms planning, slope and terrain analysis, viewshed calculation, and infrastructure design. In location analytics it also informs how signals propagate and where physical barriers shape how people actually move.
James is the head of marketing at Tamoco
Digital out of home (DOOH) is a form of marketing that uses digital displays in public places, such as bus stops or train stations, to deliver advertising messages to passersby.
James is the head of marketing at Tamoco
A digital surface model (DSM) is an elevation dataset that records the height of the Earth’s surface including everything standing on it — buildings, tree canopy, bridges and other structures. It represents the first surface a signal from above would strike.
How it differs from a DTM
A digital terrain model (DTM) describes bare earth, with surface objects stripped out. The distinction matters concretely: over a forest, a DSM traces the top of the canopy while a DTM follows the ground beneath it. Over a city, a DSM includes rooftops; a DTM gives the street level under them. Both are types of digital elevation model.
Where DSMs are the right choice
Use a DSM when the objects themselves are the subject: telecoms and line-of-sight planning where buildings block signal, solar potential assessment across rooftops, 3D city modelling, flight-path and drone corridor planning, and shadow or daylight analysis.
How they are captured
LiDAR is the usual source. A laser pulse returns several times as it strikes canopy, structures and then ground; the first return is used to build the DSM and the last return the DTM, which is why both can be derived from a single survey.
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A digital terrain model (DTM) is an elevation dataset representing the bare earth — the ground surface with buildings, vegetation and other objects removed. It answers the question of what the land itself looks like beneath whatever sits on it.
How it differs from a DSM
A digital surface model records the top of everything present, including canopy and rooftops. A DTM removes those and models the terrain underneath. Both fall under the broader heading of digital elevation model, which is why that term should always be clarified before use.
Where DTMs are the right choice
Bare-earth models are used for flood modelling and drainage, civil engineering and earthworks, slope stability and landslide risk, agricultural planning, and archaeological survey — where stripping tree cover can reveal earthworks invisible from the air.
How the ground is separated from the objects
DTMs are usually derived from LiDAR by filtering point returns to classify which struck the ground and which struck something above it. That classification is an interpretation, not a measurement, so DTM quality depends heavily on how well the filtering handles dense vegetation, steep slopes and built-up areas.
James is the head of marketing at Tamoco