Mapping & LiDAR

Mapping & LiDAR

Topographic & contour survey (DTM/DSM)

A survey of ground levels and features for planning and engineering.

Discuss this service

What you receive

  • Feature-coded CAD/GIS plan
  • DTM and/or DSM
  • Contours, spot levels and breaklines
  • Sections and survey-quality report
How we deliver

Scope & options

DTM represents bare-earth terrain; DSM retains above-ground surfaces such as roofs and vegetation.

Contours are derived from an elevation surface and inherit its datum, resolution and interpolation limits.

Breaklines preserve abrupt terrain changes that a contour-only product can smooth over.

Explore 3 service variants

Detailed feature and breakline survey

Record edges and changes in slope that matter to engineering models.

Visible-image extraction is supplemented where required.

Drainage and platform-level survey inputs

Provide terrain and levels for drainage or grading design.

Runoff, pipe sizing and flood modelling require separate engineering analysis.

Terrain processing from existing data

Produce surfaces and contours from supplied survey observations.

Source accuracy and gaps limit output accuracy.

Useful to know

Terms, explained
DTM
Digital Terrain Model: bare-earth ground surface with vegetation and structures removed where the data supports it.
DSM
Digital Surface Model: top surface including buildings, vegetation and other objects.
Contour
A line joining points of equal elevation at the stated interval and datum.
What is the difference between DTM and DSM?

A DTM represents interpreted bare-earth terrain. A DSM includes visible surfaces such as roofs and vegetation. The choice depends on the design task.

Are contours enough for a designer?

Often not. Spot levels, breaklines, feature coding and an editable terrain surface may also be required. The designer should confirm the specification.

Can this show where water will collect?

It can identify low areas and terrain flow paths. A reliable flood or drainage assessment also needs hydrological and hydraulic inputs.

Can you promise a contour interval before seeing the site?

The requested interval can be recorded, but deliverability depends on source measurements, terrain and the required accuracy. The agreed scope states limitations.

Method & limitations

Separate bare-earth DTM from above-ground DSM.

Capture breaklines and features required by the designer, not contours alone.

Specify datum, contour output and validation against project requirements.

Visible-image extraction is supplemented where required.

Runoff, pipe sizing and flood modelling require separate engineering analysis.

Source accuracy and gaps limit output accuracy.

Sources & references

Your project

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Topographic & contour survey (DTM/DSM)

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Help me ask
  • Does my designer need DTM, DSM or both?
  • Which breaklines and site features should be included?
  • What survey information is needed before drainage design?
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