This reference is written engineer to engineer, for the engineer of record or asset owner deciding how to scope and brief a reality-capture or inspection project. It sets out, for each core service, what the deliverables are, how to specify accuracy and modelled detail as two separate decisions, the standards you can write into a brief, the site constraints that govern method and time, and the information we need to return a firm quote. Throughout, accuracy and tolerance figures describe what is achievable by the relevant method and equipment class and what you can specify in a scope. They are confirmed per project against the agreed survey control and registration, and against an independent check-point test where one applies, rather than quoted as a fixed guarantee in advance. Where a standard family is named generically, that is deliberate: the exact class or clause applied is confirmed against your brief and stated in the signed deliverable. Delta Scan works under Pr Eng (ECSA) oversight, holds B-BBEE Level 1 status and carries professional indemnity cover, and delivers both directly to end clients and white-label through engineering firms across South Africa, the wider SADC region and selected Middle East markets.
As-built modelling of structures, plant and buildings
Scan to BIM
Scan to BIM converts a measured point cloud of an existing asset into an intelligent, object-based model you can interrogate, clash-check and hand into design or asset-management workflows. The capture method is chosen to suit the asset: handheld SLAM LiDAR (XGRIDS Lixel L2) for fast walkthrough coverage of plant interiors and congested spaces, static terrestrial scanning where tighter point-to-point control is needed, and VTOL drone mapping (WingtraOne) plus GNSS control (Emlid RS4) to tie roofs, structures and large sites into a real-world coordinate system. The deliverable is governed by the brief, so two questions drive the scope: how accurate the model must be (a survey or Level of Accuracy question) and how much modelled detail and embedded information you actually need (a level-of-information-need question). Those are separate decisions, and conflating them is the most common cause of over- or under-scoping. The notes below are framed around what an engineer can specify; the achievable figures are properties of the method and equipment class and are confirmed per project against the agreed control and registration, not quoted as a blanket guarantee.
Typical deliverables
- Registered, georeferenced point cloud in an agreed format (typically .rcp or .rcs for Autodesk workflows, .e57 as an open exchange, and .las or .laz where required), with a stated coordinate reference system and registration report
- Native authored BIM model in the agreed platform (commonly Revit .rvt, with IFC export to an agreed schema for open exchange under the ISO 19650 family), modelled to the agreed level of information need and discipline scope
- Two-dimensional deliverables generated from the model where required: general arrangement plans, sections, elevations and key setting-out dimensions, in DWG or PDF
- Panoramic or registered imagery, or a web-hosted point-cloud and model viewer for stakeholder access without specialist software
- Surface mesh (for example OBJ or FBX) where a watertight surface, not an intelligent model, is the actual need, for example clash visualisation or volume work
- A model methodology and accuracy statement: control used, registration approach, the achieved or agreed Level of Accuracy band, modelling assumptions, and exclusions such as obscured or inaccessible elements
How to specify accuracy
Specify accuracy and modelled detail as two separate things in the scope. For dimensional accuracy of the captured conditions, use the USIBD Level of Accuracy (LOA) framework, which defines measurable tolerance bands (LOA 10 through LOA 50) at a 95% confidence level and lets you set a different band for different systems or zones rather than one blanket number. LOA 20 to LOA 30 covers the majority of building and plant as-built work, with higher bands reserved for tight tie-in or fabrication-critical areas because they sharply increase capture and registration effort. State the LOA against the deliverable (point cloud or model) and the elements it applies to. For modelled content, specify the level of information need (the EN 17412-1 and ISO 7817-1 family that supports ISO 19650), describing geometry, information and documentation required per element rather than relying on legacy LOD labels alone. The achievable accuracy is a function of the capture method, the survey control and the registration regime, so the band is confirmed per project against agreed ground control and a registration report, never asserted as a guaranteed fixed figure in advance.
Standards you can write into a brief
- USIBD Level of Accuracy (LOA) Specification, for specifying measurable dimensional tolerance of existing-conditions capture at a stated confidence level
- Level-of-information-need standards (EN 17412-1, carried into ISO 7817-1) supporting the ISO 19650 information-management series
- LOD or Level of Development conventions (for example the BIM Forum LOD specification) where a client workflow is expressed in LOD terms
- ISO 19650 information-management standards for the wider data exchange, naming and common-data-environment requirements
- Relevant SANS or ISO survey accuracy classes and the project coordinate reference system for georeferencing and ground control
Site constraints that govern method and time
- Access and permits: confined spaces, working at height, live plant, permit-to-work systems and induction requirements, all of which govern capture method and time on site
- Line of sight and occlusion: dense pipe racks, insulation, cable trays and stored material hide elements, so agree up front what is captured as-built versus assumed or excluded
- Operational state and shutdown windows: whether capture must happen around live operations or within a shutdown, and any no-go or hot zones
- Coordinate control and georeferencing: availability of existing site control or benchmarks, or whether GNSS control needs to be established, and the target coordinate reference system
- Environmental and surface conditions: reflective, wet, dark or vibrating surfaces, dust, steam and GNSS-denied interiors that affect method selection and achievable accuracy
- Safety and compliance: site-specific PPE, hazardous-area classification, escort requirements and security or photography restrictions
- Schedule and continuity: site availability windows, and whether the asset will change between capture and modelling
What we need to return a firm quote
- Asset description and scale: type (building, structure, plant), gross floor area or footprint, number of storeys or levels, and approximate site location
- What is to be modelled: disciplines and systems in scope (for example architectural and structural shell only, or including MEP and piping), and what is explicitly excluded
- Required Level of Accuracy (USIBD LOA band) for the point cloud or model, and whether different zones need different bands
- Required level of information need (or LOD equivalent) for the model, per element where it varies
- Deliverable formats and target platform or version (for example Revit version, IFC schema, point-cloud format) and the required coordinate reference system or existing control
- Site access and constraints: live versus shutdown, permits and inductions, confined-space or height work, hazardous-area classification, and available access windows
- Whether two-dimensional drawings, a hosted viewer or other outputs are needed in addition to the model
- Programme: required delivery date or milestones, and any phasing
- Point of contact for site coordination, and any client BIM execution plan or information-requirements document to align to
Inspection, defect rating and certification
Engineering and structural condition audits
A condition audit is an engineering judgement, not a photograph book. The capture method exists to feed that judgement: imagery and point-cloud data are turned into a located, measured, severity-classified defect schedule, referenced to the code clause that governs the asset, and signed off by a Pr Eng (ECSA). What you scope here is two separate things that engineers often conflate. First, the capture fidelity, meaning how finely the asset surface and geometry are recorded and what the smallest reliably detectable and measurable defect is. Second, the assessment standard, meaning the rating framework the structure is judged against and the level of engineering certification you need on the output. Specify both explicitly. An unrated high-resolution capture gives you data and no decision; a rigorous standard applied to under-resolved data gives you false confidence. The deliverable should let you answer, for every defect, what it is, where it is, how severe it is, what the repair is, roughly what it will cost in materials, and where it sits against the applicable code, so the report can be tendered and, where needed, submitted to an insurer or regulator.
Typical deliverables
- Executive summary with risk grading and a prioritised action list, written for asset-owner and board-level decision making
- Full defect schedule: each defect located on the asset, dimensioned, classified by severity, cross-referenced to the relevant code clause, and linked to a photograph or 3D position
- Defect-tagged 3D model or navigable digital twin, with defects overlaid in position, delivered through DeltaCloud, our hosted review platform, for remote review and re-inspection comparison
- Dimensioned outputs as required: cross-sections, elevations, ovality and verticality checks, deflection or section-loss measurements, and volumetric or surface-area quantities
- Repair methodology per defect class, written to be put out to tender
- Material quantification per repair, for example concrete, reinforcement and coating, with wastage allowances
- Compliance commentary against the agreed assessment standard, for example relevant SANS or Eurocode clauses or a client-specific code
- Recommended re-inspection interval and a monitoring plan, with epoch-over-epoch comparison where the asset is on a recurring audit cycle
- Pr Eng (ECSA) letter of certification where required for insurance, regulatory or legal submission
- Source capture data on request: registered point cloud, orthomosaics and inspection imagery in agreed open formats
How to specify accuracy
Specify accuracy as two linked but distinct things, both confirmed per project after a site and data review, never quoted as a guaranteed firm-wide number. First, geometric or survey accuracy, the positional and dimensional tolerance of the model, scoped against recognised survey-accuracy bands and tied to a defined survey-control framework. Handheld and mobile LiDAR (for example the XGRIDS Lixel L2) is well suited to relative dimensional checks and as-built capture at the centimetre to low-centimetre band over a structure; survey-control-tied drone photogrammetry and VTOL mapping (for example the WingtraOne with Emlid RS4 GNSS ground control) supports tighter absolute positioning where the control network and conditions allow. State whether you need relative accuracy (dimension to dimension within the model, sufficient for most defect measurement and clearance checks) or absolute accuracy (tied to a national coordinate reference, needed for georeferenced asset registers and multi-epoch deformation work), because the two drive very different control and method requirements. Second, defect detection and classification resolution, the smallest crack width or feature reliably detected and measured at the planned capture standoff and lighting, plus the severity-rating framework. Both are set during scoping against the specific asset, access and environment, and the final Pr Eng-signed report states the accuracy and method actually achieved on that project. As a rule to scope around: detectable feature size scales with how close the sensor gets and the surface condition, so define the minimum defect of interest (for example hairline cracking versus spalling versus section loss) up front and let that drive the capture plan, rather than asking for a single headline accuracy figure.
Standards you can write into a brief
- SANS 10160 (basis of structural design and actions on structures)
- SANS 10100 (structural use of concrete) and SANS 10162 (structural use of steel)
- ISO 16311 family, in particular Part 2, assessment of existing concrete structures
- TMH19, Manual for the Visual Assessment of Road Structures (degree, extent and relevancy defect rating) for bridges, culverts, retaining walls and similar road structures
- SAICE guidance, and for industrial-structure inspection CIRIA guidance, applied as method context rather than a single prescriptive code
- Eurocode and ASTM structural and materials standards where a client or asset specifies them
- ISO 19650 information-management standards and BIM level-of-information-need conventions for model deliverables and asset-register handover
- ISO 17025 testing-and-calibration competence, referenced where any sampled or laboratory test data is incorporated
- Client-specific or sector codes (for example mining, energy, and oil and gas asset-integrity standards) supplied by the asset owner; the Pr Eng certification names the standards actually applied
Site constraints that govern method and time
- Access and working at height: structure height and reach, and whether confined-space or GPS-denied internals (shafts, ducts, vessels, flues) require a collision-tolerant indoor capture method rather than open-air UAV flight
- Airspace and flight permissions: proximity to airports, controlled airspace or restricted sites, plus any client no-fly or escort rules, and lead time for approvals where applicable
- Operational state: whether the asset can be taken offline, must be captured live, or has hot, energised, pressurised or rotating-equipment hazards that constrain standoff and timing
- Survey control and georeferencing: presence or absence of usable site control or benchmarks, and GNSS availability, which determines whether absolute accuracy is achievable or whether control must be established
- Surface, lighting and environmental conditions: corrosion, coatings, wet or fouled surfaces, dust, vibration, low light and weather windows, all of which affect detectable defect size and capture quality
- Safety regime and inductions: site-specific safety files, medicals, permits to work, escort and standby requirements, and any shutdown or isolation procedures that shape the capture window
- Logistics and remoteness: travel, accommodation and mobilisation for SADC and Middle East sites, plus equipment import or carnet considerations for cross-border work
- Data sensitivity: site security, photography restrictions, and data-handling or residency requirements for sensitive industrial assets
What we need to return a firm quote
- Asset type, quantity and key dimensions (for example three concrete cooling towers, with height and shell area, or a 40 m span road bridge), ideally with a sketch, photograph or location
- Site location and access details, including travel constraints and whether the work is in South Africa, SADC or the Middle East
- The assessment standard required and the level of certification needed (for example TMH19 rating, SANS-based concrete assessment, or a named client code, and whether a Pr Eng certification letter for insurance or regulatory submission is required)
- The minimum defect of interest and the decision the audit must support (for example hairline crack mapping, spalling and section-loss quantification, or a remaining-life or fitness-for-service call), so capture fidelity can be set
- Whether absolute (georeferenced) accuracy is needed or relative dimensional accuracy is sufficient, and any existing site survey control or coordinate reference to tie into
- Asset records available: original drawings, prior inspection or audit reports, and maintenance history
- Operational and access constraints: whether the asset can be shut down or isolated, whether there are confined-space or GPS-denied internals, and what standoff or no-fly limits apply
- Site safety and compliance requirements: safety file, inductions, medicals, permits, escort or standby, and any data-handling or photography restrictions
- Required output formats and delivery (for example signed PDF report plus defect-tagged model via DeltaCloud, and whether raw point cloud and imagery are to be handed over), and any integration target such as an existing asset-management system
- Whether this is a one-off audit or a recurring, multi-epoch monitoring programme, and the required reporting and re-inspection cadence
- Target dates or shutdown windows, and the contracting basis, including whether this is a direct asset-owner engagement or white-label capture delivered under an engineering firm own report
Locating and mapping buried services
GPR and subsurface utility detection
Subsurface utility detection answers a question records alone cannot: where the buried services actually are, and how confident you can be in that position before you commit a design or break ground. The work combines complementary geophysics, electromagnetic location for conductive and traceable services, and ground-penetrating radar (GPR) for non-conductive lines (plastic, clay, concrete, fibre ducts) and other anomalies, because no single method sees everything in every ground condition. The single most useful thing you can do when scoping is to state the confidence level you need rather than just asking for a utility survey. Detection confidence is governed by an established quality-level framework (QL-D desktop records, QL-C correlated to visible surface features, QL-B geophysical detection, QL-A physical verification by exposure). Specifying the target quality level per zone, and accepting that some services may only be resolvable to a lower level in difficult ground, keeps the scope honest and the deliverable defensible. Detection reduces but never eliminates risk, so a non-destructive survey is a designating exercise, not a guarantee that the ground is clear for excavation.
Typical deliverables
- Two-dimensional utility plan (CAD: DWG or DXF) with detected services drawn by type, each line tagged to its quality level (QL-D to QL-A) so the reader sees the confidence behind every position
- Georeferenced output tied to a stated coordinate system and datum (Hartebeesthoek94 and the relevant Lo system, or a client grid), with GNSS-controlled survey marks where surface control is required
- Depth-to-top annotations where ground conditions allow them, with depths flagged as indicative and method-dependent rather than absolute
- Utility register or schedule listing each detected service by type, approximate size where determinable, detection method and quality level
- GIS-ready geospatial deliverable (shapefile, GeoPackage or GeoJSON) with attributes for type, method, confidence and depth where requested
- Annotated survey report covering methods used, equipment, ground conditions, coverage achieved, areas of reduced confidence, and any zones recommended for QL-A verification
- Overlay against client design or existing as-builts, and clash or proximity flags, where the design files are provided
- Optional integration of subsurface detections with above-ground reality-capture data (LiDAR or drone topo) into a single composite model where the wider project requires it
How to specify accuracy
Accuracy on subsurface work is best specified through quality level rather than a single millimetre tolerance, because what is achievable depends heavily on service type, depth and ground conditions. An engineer can specify: a target quality level per zone (for example QL-B detection across the site with QL-A verification at defined crossings or tie-in points); horizontal position confidence consistent with the chosen quality level (QL-B geophysical designation is typically specified to the order of a few hundred millimetres in workable ground, with QL-A exposed positions specifiable to the tens-of-millimetres order); whether depth-to-top is required, and the understanding that GPR depth estimates carry wider uncertainty than horizontal position and degrade with depth and soil moisture; and the survey control accuracy for georeferencing the detections. The achievable confidence in any given zone is method-dependent and ground-dependent, so the realistic quality level per area is confirmed per project once site conditions are known, and zones where the specified level cannot be reached non-destructively are reported as such rather than overstated.
Standards you can write into a brief
- PAS 128 (BSI specification for underground utility detection, verification and location) and its QL-D to QL-A quality-level framework
- ASCE 38-22 Standard Guideline for Investigating and Documenting Existing Utilities (and its predecessor ASCE 38-02), the recognised standard of care for collecting and depicting subsurface utility data
- SANS construction-regulation and occupational-health-and-safety requirements relevant to excavation and working near buried services, confirmed against the applicable current edition per project
- ISO 19650 information-management standards where the utility model feeds a wider BIM or common-data-environment deliverable
- Asset-owner and utility-authority standards (for example Eskom, Transnet, municipal and mine-specific service-location and permit-to-dig requirements) where the site sits on or near third-party infrastructure
Site constraints that govern method and time
- Ground conditions drive what GPR can resolve: high-clay, saturated or highly conductive soils attenuate the radar signal and reduce depth penetration, so achievable confidence varies across a single site
- Surface type and obstructions: reinforced concrete, rebar mesh, dense hardstanding and heavy surface clutter can mask or mimic services and limit coverage
- Congested or legacy corridors where many services run in parallel or stacked can be difficult to separate, and abandoned or unrecorded lines may be present
- Non-conductive and unmarked services (plastic, clay, fibre, empty ducts) cannot be traced by electromagnetic location and rely on GPR or tracer access
- Live-site and permit constraints: induction, permits to work, hot-work or excavation permits, supervised access, and restricted working windows on operating mines, energy and oil-and-gas sites
- Vegetation, terrain and standing water restricting trolley or cart-mounted GPR access, sometimes requiring handheld survey
- Where QL-A verification is required, the need for, and approval of, non-destructive exposure (vacuum or hydro excavation, or trial holes) booked as a separate controlled activity
- Coordinate framework and existing control: availability of site survey control and the agreed datum or Lo system for georeferencing detections
What we need to return a firm quote
- Site location or locations and total area or linear extent of the zones to be surveyed (a marked plan, KMZ or coordinates is ideal)
- The quality level required (QL-D to QL-A) and whether it is uniform across the site or differs by zone or by specific crossings or tie-in points
- What you need to find: all services, or specific target utilities (for example HV cable, water main, fibre), and whether depth-to-top is required
- Surface conditions across the survey area (open ground, paved, reinforced concrete, vegetation, congestion) and any known buried services or existing as-builts or records to start from
- Required deliverable formats (CAD, GIS, report) and the coordinate system and datum the output must be delivered in, plus any site survey control available
- Whether QL-A physical verification (vacuum excavation or trial holes) is in scope, and who arranges and permits it
- Site access and safety regime: ownership, induction and permit requirements, working-hours or shutdown windows, and any escort or supervision conditions
- Site type and sector (mine, energy, oil and gas, infrastructure, insurance or forensic) and any client or authority standards the survey must satisfy
- Programme: required start window, deadline, and whether the survey must integrate with above-ground topo or reality-capture in the same mobilisation
- Whether the work is for an end client (engineer of record or asset owner) or delivered white-label to an engineering firm, including any client-branding requirements on the deliverable
Aerial mapping, volumetrics and topographic
Drone and LiDAR survey
Aerial mapping and LiDAR survey covers VTOL drone photogrammetry (orthophoto, surface and terrain models), aerial and handheld LiDAR point clouds, and the topographic and volumetric products derived from them. The right method depends on what you are trying to resolve. Drone photogrammetry suits open terrain, stockpiles, pit shells, tailings facilities and large topographic extents where a dense, colourised surface is enough. LiDAR earns its place where you need to penetrate vegetation, capture under canopy or steep walls, or where the deliverable must separate the bare-earth surface from cover. The single decision that drives both cost and defensibility is the ground control and check-point regime: accuracy is established against an independently surveyed control network, then reported against it, so an engineer should scope the control and the acceptance test, not just the flight. Specify the achievable accuracy class for the chosen method and have it confirmed per project against your control, rather than relying on a headline number. Outputs are delivered in your project datum and Lo band so they drop straight into your design environment.
Typical deliverables
- Classified or unclassified 3D point cloud (LAS or LAZ), with bare-earth and off-ground returns separated where LiDAR or hybrid capture is used
- Digital Terrain Model (DTM, bare earth) and Digital Surface Model (DSM) as raster grids or TINs
- Contours at a specified interval, generated from the DTM and clearly labelled as such
- Orthophoto or orthomosaic at a stated ground sample distance (GSD)
- Topographic or detail survey as CAD linework and surveyed features (DWG or DXF), drawn to your layer and feature convention
- Volumetric report: cut and fill or stockpile volumes against a stated base surface or datum plane, with the method and tonnage factor (if applied) recorded
- Cross-sections and long-sections at specified chainage and interval
- Survey or accuracy report stating control used, check-point residuals, achieved RMSE against checks, datum, projection (Lo band) and vertical reference
- Web-viewable model or tiled deliverable for review and measurement, where requested
- Metadata and a processing and methodology statement describing method class and acceptance criteria
How to specify accuracy
Specify accuracy as a target class for the chosen method, expressed as horizontal and vertical RMSE against independently surveyed check points, and have it confirmed per project once control is established. As a guide to what each method class can achieve under good conditions: drone photogrammetry with surveyed ground control can, under good control and conditions, support horizontal and vertical RMSE in the order of one to three times the GSD (commonly a few centimetres on engineering-scale flights), reported against the ASPRS standard and confirmed per project against independent check points, with vertical accuracy the limiting factor and dependent on control density and surface texture; handheld and aerial LiDAR (for example the XGRIDS Lixel L2 handheld, or drone-borne LiDAR with GNSS, IMU and ground control) supports relative accuracy at the centimetre level, with absolute accuracy governed by the control network and georeferencing. Always tie the requirement to a named standard family (for example the ASPRS Positional Accuracy Standards for Digital Geospatial Data, which report horizontal and vertical RMSE in non-vegetated and vegetated terrain) and to a stated GSD, point density and contour interval. State the acceptance test in the scope: number and distribution of independent check points and the pass or fail residual threshold. Avoid specifying a single accuracy figure without also specifying the GSD, control regime and the surface it applies to, because bare-earth accuracy under vegetation is method-limited and should be scoped separately. The achievable class is method and equipment dependent and is confirmed per project against your control, not guaranteed as a fixed number in advance.
Standards you can write into a brief
- ASPRS Positional Accuracy Standards for Digital Geospatial Data (Edition 2), reporting horizontal and vertical RMSE against independent check points
- South African Coordinate Reference System: Hartebeesthoek94 datum and the Lo (Gauss Conform) projection, with the correct Lo band and central meridian specified per site
- SACAA Civil Aviation Regulations Part 101 (RPAS) governing commercial drone operations, including the Remote Operator Certificate (ROC), Remote Pilot Licence (RPL) and the operating limits (height ceiling, visual-line-of-sight, aerodrome stand-off and third-party liability cover), as per the current edition and any specific CAA approvals held, confirmed per operation
- ISO 19650 information-management standards for deliverable structuring, naming and exchange where the project runs to a BIM or common-data-environment workflow
- LOD or level-of-information-need conventions for agreeing model and feature detail
- Relevant SANS or ISO survey and geospatial accuracy classes where a client or authority specifies them; the applicable class is confirmed against the project brief
Site constraints that govern method and time
- Airspace and regulatory clearance: proximity to aerodromes, controlled airspace, heliports and restricted or national key-point areas, which may require SACAA approval or notice and can constrain or prevent drone flight
- Ground control access: safe, surveyable points across the full extent, including the far edges and any change-of-grade areas needed to constrain vertical accuracy
- Vegetation and canopy: dense bush, crops or tree cover that obscure bare earth and push the work toward LiDAR or a hybrid method, with bare-earth accuracy scoped separately
- Vertical structure and confined areas: pit walls, highwalls, shafts, stockpile faces, tanks and under-structure zones that drone nadir capture cannot see and that suit handheld LiDAR or oblique capture
- GNSS conditions: open sky for base, rover and drone georeferencing, with multipath or obstruction near walls, headgear and steelwork affecting absolute accuracy
- Operational environment: live plant, blasting schedules, traffic, dust, induction and permit-to-work requirements, and any explosion-risk or restricted zones that limit equipment and timing
- Weather and light: wind limits for the VTOL platform, rain, low cloud and sun angle affecting both flight windows and orthophoto quality
- Site safety and access logistics: escort requirements, working-at-height or near-water controls for ground control placement, and travel time for SADC or remote sites
- Surface change over time: active earthworks, moving stockpiles or water level, which fix the as-flown date and require a clear epoch for volumetrics
What we need to return a firm quote
- Site location or locations and total area or extent (a boundary KML, shapefile or marked map is ideal), plus the number of separate sites or visits
- Purpose of the survey and the primary deliverable (topographic detail, DTM or DSM, contours, volumetrics, orthophoto, or a combination)
- Required accuracy class or tolerance, and the contour interval and GSD if already specified, so the method and control regime can be set
- Datum and projection required (Hartebeesthoek94 and the Lo band or central meridian), and the vertical reference, if other than the project default
- Deliverable formats and conventions: file types (LAS or LAZ, DWG or DXF, raster, PDF), CAD layering or feature codes, and any client template
- Whether bare-earth under vegetation is required, and the nature and density of any vegetation or canopy on site
- Presence of vertical or confined features (pit walls, stockpile faces, shafts, structures, under-canopy areas) that need LiDAR or oblique capture rather than nadir drone only
- Existing survey control on site, or whether Delta Scan is to establish and survey the control network
- Volumetrics detail if applicable: base surface or datum plane, whether a prior surface is provided, and any tonnage or density factor to apply
- Airspace and access context: proximity to aerodromes, any controlled or restricted airspace, national key-point status, and on-site induction, permit, escort or safety requirements
- Required timeframe, the as-flown or capture date that matters for volumetrics or change, and any repeat or monitoring frequency
- Site access and logistics: nearest town, road access, accommodation needs for remote or SADC sites, and any client-imposed working windows
- Whether the deliverable is white-label (issued to or through an engineering firm) or direct to the asset owner or engineer of record, and the named recipient for the survey report
Georeferenced spatial data for design and planning
GIS and topographic survey
This service produces georeferenced topographic and spatial datasets that an engineer can take straight into design, GIS, asset-management or planning workflows. The output is a survey of the ground surface and visible features (levels, breaklines, edges of infrastructure, services covers, watercourses, vegetation lines, hardstanding) tied to a known coordinate reference system, rather than a raw point cloud you still have to interpret. Method is selected to suit the site and the accuracy you specify: WingtraOne VTOL drone photogrammetry and aerial LiDAR for open or large-area topography and corridors, XGRIDS Lixel L2 handheld LiDAR for dense built-up zones, plant and areas under canopy or cover, and Emlid RS4 GNSS for ground control, check points and discrete feature pick-ups. All deliverables are referenced to the South African system (Hartebeesthoek94 and WGS84, Lo projection on the relevant central meridian) or to a client grid you nominate, with the vertical datum stated explicitly. ECSA-registered (Pr Eng) oversight is available where the dataset feeds a design or a statutory submission. The key brief decisions for the engineer are: what coordinate and height datum the data must sit in, what positional accuracy class the design actually needs, and what features and detail level must be captured. Final figures are confirmed per project against the control framework on site and are not guaranteed in advance.
Typical deliverables
- Georeferenced point cloud (LAS or LAZ, or E57), classified to ground and key feature classes where specified
- Digital terrain model (DTM, bare earth) and or digital surface model (DSM) as a TIN or gridded raster (GeoTIFF), with stated grid spacing
- Contours at a client-specified interval, plus spot heights and breaklines
- Two-dimensional topographic or detail survey drawing (DWG or DXF) layered to a client or in-house standard, with feature codes
- Orthomosaic or orthophoto (GeoTIFF) at a stated ground sample distance, georeferenced
- GIS-ready vector layers (shapefile, GeoPackage or file geodatabase) with an attribute schema agreed up front
- Coordinate listings of control, check points and surveyed features (CSV), with the coordinate reference system, projection and vertical datum recorded
- Survey report stating method, control framework, datum, achieved accuracy against independent check points, date of capture and any occluded or estimated areas
- ISO 19115-style metadata where the dataset must enter a spatial data infrastructure
How to specify accuracy
Specify the accuracy class your design genuinely needs rather than defaulting to the tightest. For aerial photogrammetry and LiDAR, the achievable horizontal and vertical accuracy scales with the chosen ground sample distance, flying height, control density and check-point regime, and is best stated against the ASPRS Positional Accuracy Standards for Digital Geospatial Data (Edition 2) as an RMSE value, for example a stated horizontal RMSE and a stated vertical RMSE for the bare-earth model, agreed before flight. For handheld and terrestrial LiDAR in built-up or covered areas, specify relative (local) accuracy for clash and as-built work separately from absolute (georeferenced) accuracy, because the two differ and the brief should make clear which governs. Ground control and discrete GNSS pick-ups using RTK off a CORS or base reference are typically specified at the survey-grade centimetre level. The practical approach is: nominate a required accuracy class and an independent check-point tolerance in the scope, and the achieved figure is then verified per project against those check points and reported in the survey report. Accuracy classes quoted here are achievable by the relevant method and equipment class and are confirmed per project; they are not a guaranteed pre-stated Delta Scan number.
Standards you can write into a brief
- ASPRS Positional Accuracy Standards for Digital Geospatial Data (Edition 2, 2023), the RMSE-based positional accuracy classes for photogrammetry, LiDAR and UAS mapping
- ISO 19157 (Geographic information, data quality), for positional accuracy, completeness and logical-consistency reporting
- ISO 19115 (Geographic information, metadata) family, for datasets entering a spatial data infrastructure
- Spatial Data Infrastructure Act 54 of 2003 (SASDI), with the ISO 19144 land-cover and classification systems family (and any SANS adoption) where data must be SASDI-compatible or classified
- South African reference framework: Hartebeesthoek94 datum (WGS84 ellipsoid) and the Lo (Gauss conformal) projection administered by CD: NGI
- ISO 19650 information-management conventions and level-of-information-need conventions where the topographic survey feeds a BIM or digital-twin workflow
- Relevant SANS or ISO survey accuracy and GIS data-quality classes as nominated by the client or engineer of record
Site constraints that govern method and time
- Airspace and flight permissions: drone capture needs clear airspace and may be restricted near airports, controlled airspace, mines, power stations and national key points, with lead time for any required authorisations
- Tree canopy, dense vegetation and overhead cover degrade aerial line of sight to the ground and may need handheld LiDAR or supplementary ground survey to recover true ground level
- GNSS sky view: deep cuttings, tall structures, dense plant and indoor or under-deck areas weaken or block satellite reception, affecting control and direct georeferencing
- Availability and condition of existing survey control or trig beacons on site, and whether a local site grid or transformation must be honoured
- Site access, induction, permit-to-work, escort and PPE requirements on operating mining, energy and oil-and-gas sites, and any live-plant or exclusion zones
- Ground cover and surface state: standing water, flooding, crops or stockpiles obscure the true terrain surface and should be flagged in the brief
- Weather and light windows for aerial capture (wind, cloud base, rain) and seasonal vegetation that affects what the ground model can resolve
- Area extent, terrain relief and corridor length, which drive flight planning, control spacing and the number of mobilisations
- Security, sensitivity or confidentiality constraints on imagery and data leaving site
What we need to return a firm quote
- Site location or locations and the exact survey extent or boundary (a marked-up plan, KML or shapefile, or coordinate list is ideal), plus total area or corridor length
- Required coordinate reference system, projection (for example Hartebeesthoek94 Lo on the relevant central meridian, or a nominated client grid) and the vertical datum for heights
- Required positional accuracy class (horizontal and vertical), stated as an ASPRS or RMSE class or an equivalent tolerance, and the intended use of the data (design, volumes, GIS, planning, as-built)
- Feature list and level of detail to be captured (which services, structures, edges, levels, contours), the contour interval, and any GIS attribute schema required
- Deliverable formats and the CAD or GIS layering or feature-coding standard to be followed
- Whether existing site control, a trig framework or a site-specific transformation must be used, and any prior survey data to tie into
- Site access and safety conditions: ownership, induction or permit requirements, escort, operating-plant or exclusion zones, and any security or data-confidentiality constraints
- Airspace context for drone capture (proximity to airports, mines, key points or controlled airspace) and who holds or arranges any permissions
- Programme: required survey date or dates, reporting deadline and whether repeat or monitoring epochs are needed
- Whether Pr Eng (ECSA) oversight, certification or a signed-off deliverable is required, and whether the engagement is direct or white-label under the client own brand