Resources

LiDAR and emissions monitoring glossary

Plain-language definitions of the terms used in LiDAR stockpile measurement, bulk inventory management and air emissions monitoring, with links to the Altamus pages where each one matters.

This glossary covers 42 terms across two areas Altamus works in: measuring bulk material with LiDAR stockpile monitoring, and collecting compliance data with STACguard emissions data acquisition. Select a letter to jump to it.

0–9

40 CFR Part 60: The federal New Source Performance Standards (NSPS). Its subparts set emission limits and monitoring requirements for specific source categories, such as boilers, cement kilns and fertilizer plants, and its appendices define how continuous monitors must be certified and quality-assured. Part 60 monitoring for boilers
40 CFR Part 75: The federal continuous emissions monitoring rule for the Acid Rain Program and related trading programs. It sets detailed requirements for monitoring, quality assurance, data substitution and electronic reporting of SO2, NOx, CO2 and heat input, mainly at electric generating units. STACguard for steam generation

A

Angle of repose: The steepest angle at which a loose bulk material can be piled without sliding. It depends on particle size, shape and moisture, and it controls how much material a given floor area or bin can hold.
Angular resolution: The angle between neighboring measurements in a scan. A smaller angle means more points and more detail but a longer scan. The EOS2 completes a full spherical scan in about 3 minutes at 1° angular resolution. EOS2 specifications
API (application programming interface): A defined way for one software system to request data from another. Hyperion exposes an API so volume and tonnage results can flow automatically into inventory, ERP or reporting tools. Hyperion integrations

B

Book-to-physical variance: The difference between the inventory a company’s records say it has (book inventory) and what is actually on the ground (physical inventory). Large or unexplained variances usually lead to write-downs at audit time. Reducing variance at fertilizer plants
Bulk density: The mass of a loose material per unit of volume, including the air between particles, such as tons per cubic yard. Bulk density converts a measured stockpile volume into tonnage and varies with material, compaction and moisture.

C

Calibration drift check: A routine test, usually daily, in which a gas analyzer measures reference gases of known concentration. The difference between the reading and the known value (the drift) shows whether the monitor is still measuring within allowed limits. Automated calibrations in STACguard
CEMS (continuous emissions monitoring system): The complete set of equipment that continuously measures pollutant concentrations and related parameters in a stack: sample handling, gas analyzers, flow or opacity monitors, and a data acquisition system that records the results. STACguard for CEMS
Class 1 laser: The safest laser classification under international laser safety standards. A Class 1 laser product is eye-safe under all conditions of normal use, which allows the EOS2 to operate around people without special controls. EOS2 LiDAR sensor
CO (carbon monoxide): A colorless, odorless gas produced by incomplete combustion. CO is monitored at many combustion sources as both a regulated pollutant and an indicator of combustion efficiency.

D

DAHS (data acquisition and handling system): The term used in federal CEMS rules, especially Part 75, for the computer system that collects monitor data, applies quality-assurance and substitution rules, calculates emissions and generates reports. In practice it is often used interchangeably with DAS. STACguard DAS
DAS (data acquisition system): Software and hardware that collect readings from analyzers and sensors, validate and average them, trigger alarms and produce compliance reports. STACguard is a web-based DAS for emissions and ambient air monitoring. STACguard
Digital twin: A digital model that mirrors a physical asset and is updated with measured data. In stockpile monitoring, the 3D mesh built from each scan acts as a digital twin of the inventory on the ground. Hyperion 3D models

E

ERP (enterprise resource planning): Business software, such as SAP or JD Edwards, that manages inventory, purchasing, production and finance in one system. Feeding measured stockpile quantities into an ERP keeps book inventory aligned with reality.

F

Fenceline monitoring: Measuring air quality at the boundary of a site to detect dust, vapors or gases leaving the property. It is common at remediation, industrial and construction sites that must protect nearby communities.
Field of view: The horizontal and vertical extent a sensor can observe. The EOS2 has a 360° × 180° field of view, meaning it can measure in every direction around its mounting point. EOS2 field of view

I

IP54 rating: An ingress protection rating under the IEC 60529 standard. The 5 means the enclosure is protected against dust in amounts that would interfere with operation, and the 4 means it resists water splashed from any direction.

L

LiDAR: Light Detection and Ranging: a method of measuring distance by timing laser pulses reflected from surfaces. Many measurements taken in different directions build a 3D point cloud of the surroundings. How LiDAR monitoring works

M

Mesh: A 3D surface made of connected triangles (or other polygons). Stockpile software builds a mesh from a point cloud so it can calculate the volume enclosed between the pile surface and its base. Hyperion 3D models

N

NOx (nitrogen oxides): A family of gases, mainly nitric oxide (NO) and nitrogen dioxide (NO2), formed when fuel is burned at high temperature. NOx contributes to smog and acid rain and is one of the most commonly monitored stack pollutants.
NPT (National Pipe Thread): The standard tapered thread for pipes and fittings in the United States. The EOS2 mounts on a 3/4" NPT fitting, so it can be installed with ordinary pipe hardware on poles, brackets or trusses. EOS2 mounting

O

O2 diluent: Oxygen measured alongside pollutants in a stack. Because excess air dilutes pollutant concentrations, O2 (or CO2) readings are used to correct results to a standard oxygen level so they can be compared fairly with emission limits.
Occlusion: An area hidden from a sensor’s line of sight, for example behind a wall, a machine or the far side of a tall pile. Occluded areas produce no points, so good sensor placement, extra sensors and gap flagging matter for accurate volumes. Accuracy and quality assurance
Opacity: The degree to which emissions in a stack or plume block light, expressed as a percentage. It is used as an indicator of particulate emissions and is measured by continuous opacity monitors or trained visual observers.

P

PCD file: The Point Cloud Data file format, a simple format for storing 3D points and optional attributes such as intensity or color. It is widely used in open-source point cloud tools. View an EOS2 scan
Photogrammetry: Building 3D measurements from overlapping photographs, often taken by a drone. Software matches features between images to reconstruct surfaces. It is passive, so results depend on lighting and surface texture. LiDAR vs. drone surveys
PM10 and PM2.5: Particulate matter with diameters of 10 micrometers or less (PM10) and 2.5 micrometers or less (PM2.5). The smaller the particles, the deeper they reach into the lungs, which is why both are regulated air pollutants.
Point cloud: A set of 3D points, each with X, Y and Z coordinates, that together describe the surfaces of objects and terrain. Point clouds are the raw output of LiDAR scanners and photogrammetry. Point cloud generation with EOS2
Point cloud merging (stitching): Combining several point clouds into one dataset so an area can be covered from multiple viewpoints. Merging fills occluded areas and extends coverage beyond the range of a single sensor. Multi-sensor coverage in Hyperion

R

RATA (relative accuracy test audit): A periodic test in which an independent reference method is run alongside a CEMS and the two sets of results are compared. Passing the RATA demonstrates that the installed monitors are measuring accurately. RATA support in STACguard
Registration: Aligning point clouds captured from different positions or at different times into one shared coordinate system. Accurate registration is required before scans can be merged or compared.
Rolling average: An average recalculated each period over a fixed window that moves forward in time, such as a 30-day rolling average updated every day. Many emission limits are written as rolling averages rather than single readings. Rolling averages at cement kilns

S

SO2 (sulfur dioxide): A gas formed mainly when sulfur-containing fuels or raw materials are burned or processed. SO2 is a regulated pollutant and a precursor to acid rain and fine particulate.
Soil reclamation unit (dirt burner): A plant that treats petroleum-contaminated soil with heat, usually in a rotary drum, to drive off the hydrocarbons before the exhaust passes through air pollution controls. These units typically need a single continuous monitor on the stack under their air permit. STACguard for soil reclamation units
Stockpile: A pile of bulk material, such as aggregate, coal, clinker, fertilizer, grain or feed, held in storage indoors or outdoors until it is used or shipped. Stockpile monitoring by industry
Surface reconstruction: Turning scattered points into a continuous surface. Methods such as Poisson surface reconstruction estimate a smooth surface that fits the measured points and fill small gaps between them. From point cloud to volume

T

Time of flight: Measuring distance by timing how long a signal takes to travel to a target and back. With light, distance equals the speed of light multiplied by the round-trip time, divided by two. LiDAR basics
Tonnage: The weight of material in a stockpile, usually reported in short or metric tons. It is calculated by multiplying measured volume by the material’s bulk density.
Truck ticket: The record of material weight produced when a truck crosses a scale on delivery or shipment. Ticket totals drive book inventory, but scale errors, moisture changes and handling losses mean they can drift from what is physically on site. Tickets vs. scans at a ready-mix plant

V

VOC (volatile organic compound): Carbon-based chemicals that evaporate readily at room temperature, such as solvents and fuel vapors. Many VOCs contribute to ground-level ozone and some are hazardous, so they are monitored at remediation and industrial sites.
Volumetric measurement: Determining how much space a material occupies, typically in cubic yards, cubic feet or cubic meters. For stockpiles it means calculating the volume between the measured pile surface and the ground or bin floor. Hyperion volume measurement

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