Terrain and Mining Engineering Glossary

A raster grid in which every cell stores a ground elevation. It is the base layer for almost every terrain calculation: volumes, cross-sections, slope, hydrology and contours are all derived from it.

In practice 'DEM' is used both as the umbrella term for any elevation grid and, more narrowly, as a synonym for a bare-earth model. When it matters, say DSM or DTM instead.

An elevation surface that includes everything standing on the ground: buildings, vegetation, equipment and stockpiles. It is what a photogrammetry pipeline produces first, before any filtering.

A DSM is the right surface for measuring a stockpile, and the wrong surface for a ground volume through a wooded area — the trees would be counted as material.

A bare-earth elevation surface, with buildings and vegetation removed so only the ground remains. It is what earthwork quantities and design surfaces should be computed against.

A DSM is the surface as captured, including objects on it; a DTM is the ground underneath after those objects are removed. Over open ground the two are nearly identical; over vegetation or structures they differ by the height of whatever is standing there.

The distinction decides the number, not the picture. A volume computed on a DSM where a DTM was intended is wrong by roughly the object height times the area they cover.

A surface built from triangles connecting measured points, rather than from a regular grid of cells. It follows breaklines and dense survey points exactly, which is why design surfaces are often stored as a TIN.

A TIN and a raster DEM describe the same thing in different ways: a TIN is efficient where point density varies a lot, a raster is efficient where it is uniform.

A set of measured 3D points, usually from LiDAR or from dense image matching in photogrammetry. It is a measurement, not yet a surface — points must be classified or rasterized before you can compute volumes on them.

An aerial image corrected for camera tilt and terrain relief so that every pixel sits at its true map position and distances can be measured on it directly.

An uncorrected aerial photo is not an orthophoto: on sloping ground the displacement can be metres.

The ground distance represented by one pixel of an image, usually in cm/pixel. A 2 cm GSD means each pixel covers 2 cm of ground.

GSD sets the finest detail you can see, but it is not the same as accuracy — a 2 cm GSD survey with poor control can still be a metre out in absolute position.

A shaded-relief rendering that lights the terrain from a chosen sun angle so slopes and ridges read as shape rather than as colour values.

A line joining points of equal elevation. The vertical distance between successive lines is the contour interval, and how tightly the lines pack together is how steep the ground is.

A line along which the terrain changes slope abruptly — a crest, a toe, a road edge, a ditch. Surfaces that ignore breaklines round off exactly the features that matter most.

Material that has to be removed to bring the existing ground down to a design surface or level. In a cut/fill result it is the volume where the existing surface is above the design.

Material that has to be added to bring the existing ground up to a design surface or level — the volume where the design is above the existing surface.

The paired calculation of how much has to be removed and how much has to be placed between two surfaces, or between a surface and a level. Reported as two separate figures plus their net.

The net figure alone hides the work: 10,000 m³ cut and 10,000 m³ fill nets to zero but is still 20,000 m³ of moving.

The platform level at which cut volume equals fill volume, so material neither has to be imported nor hauled off site. Found where the cut and fill curves cross.

Volume computed from cross-sectional areas taken at regular stations along an alignment, then integrated between them — the classic road and channel earthwork method.

The station interval controls accuracy: sections too far apart miss the shape of the ground between them.

A cumulative plot of cut minus fill along an alignment. Its rising and falling sections show where material is surplus or short, and therefore how far it has to be moved.

A pile of extracted or processed material held on site. Its volume is measured above a reference base and multiplied by material density to give tonnage for inventory.

The mass of material per unit of volume as it sits, including the void space between particles — typically t/m³. It is what converts a measured volume into a tonnage.

Bulk density differs from the density of the rock itself, and it differs again between in-situ and stockpiled material.

The increase in volume when material is excavated and loosened. 1 m³ of rock in the ground can occupy 1.3–1.6 m³ in a truck, which is why survey volumes and truck counts rarely agree.

The surface or flat elevation a volume is measured against. Changing it changes the answer, so it belongs in the report next to the number.

Comparing two surveys of the same area to find where material was added and where it was removed, reported as deposition and erosion volumes rather than a single net figure.

The smallest surface change that can be distinguished from survey noise. Differences below it are not evidence of movement, however clean the map looks.

The layout of blastholes on a bench, defined by burden, spacing, the arrangement (square or staggered) and the orientation of the grid relative to the free face.

The distance from a blasthole to the nearest free face, measured perpendicular to it. It is the rock the hole actually has to break, and it is the parameter fragmentation is most sensitive to.

On a battered face the burden is not what the plan view shows: an inclined hole gets progressively more rock in front of it with depth, so the toe is where a pattern goes tight.

The distance between adjacent holes along a row. Together with burden it sets the pattern area each hole is responsible for, and therefore the powder factor.

The extra depth drilled below the design floor so the floor breaks cleanly instead of leaving a hard toe. Too little leaves a high floor; too much damages the bench below.

Inert material placed in the top of a blasthole to confine the explosive gases. Too little stemming vents energy into the air as noise and flyrock instead of into the rock.

The mass of explosive used per unit of rock broken, in kg/m³ or kg/t. It is the standard way blast energy is compared between patterns.

The open surface a blast can break towards. Without one, rock has nowhere to move and the energy goes into shaking the ground rather than fragmenting it.