Photogrammetry Products
Digital Terrain and Elevation Models (DTM and DEM)
Digital Terrain Models are one of the most common photogrammetric products used to represent the Earth's surface elevation as a set of points. These models, derived chiefly from aerial imagery, offer users the ability to visualise and manipulate the surface of the earth. DTMs are used to produce orthophotographs and contour data.
Buildings can be added to the models creating 3D cityscapes and various planning applications such as clutter data for broadcasters. Draping aerial photographs or topographic map detail over the models gives a more detailed, very visual view that can be looked at from many angles.
Terralink International’s DTM, DEM and 3D Cityscapes are used for a variety of planning applications such as earthquake and flood prediction models, environmental planning, sound and vibration analysis, roading design and earth works. Models can be supplied in GIS and CAD formats as well as movie type fly throughs, and digital and hardcopy scenes.
Close range photogrammetry assists in crime scene mapping and set design and modelling for the film industry.
Orthophotographs
An orthophoto combines the visual advantages of a photo with the accuracy of a map. Starting with an aerial or satellite photo, distortions caused by the curvature of the earth, camera tilt and terrain relief are removed through the process of orthorectification. The completed orthophotos are geographically referenced and provide a key data layer in a Geographic Information System (GIS). Terralink has the most extensive collection of high quality aerial imagery available for New Zealand.
3D Capability
Using detailed terrain models, aerial photography and highly accurate 3D cityscape models, Terralink International are able to produce interactive 360o virtual reality environments, fly throughs and animations of existing and/or proposed future developments. Visually impressive virtual reality models can be created for your area of interest be it the whole of New Zealand or focusing on a new property development.
Data
3D buildings are stereo captured typically to a spatial accuracy of 0.5 metres from 1:5,000 – 1:8,000 imagery and Digital Terrain Models up to 0.5 metres (subject to the usual constraints – photo scale, AT etc). Orthophotography is often generated to a resolution of 0.1 metre GSD (Ground Sample Distance).
For projects covering a large area, satellite imagery may be a preferred choice. Satellite imagery is available in resolutions as high as a 60cm pixel size with a re-fly frequency of three days.
Building 'textures' can be created from a mix of digital terrestrial photos and oblique aerial photos. Artist impressions can also be used for proposed building projects. Textured buildings can be combined with a digital terrain model and “draped” orthophotography to create a 3D digital environment.
The digital output is completely flexible; the data can be used live on the screen, across the Intranet, inside a PowerPoint presentation or as a still image within a printable document.
Still Images
Using 3D modelling techniques, still images can be produced from any viewpoint. These views can be anything from a view of the entire country down to a single residence. We can even create views from locations that would be hard or impossible to get to in real life. Some projects still views have been used for include:
- Public consultation and resource consent
- Showing bird migratory patterns
- Real estate
- Television news
- Tourism
3D Cityscapes
3D cityscapes are true perspective models of the Auckland and Wellington central business district buildings and land form, and are predominantly used by councils, planners and developers. These models are excellent visualisation and planning tools allowing the user to perform virtual fly throughs, conduct line of sight analysis, wind tunnel testing and noise and pollution modelling. Cityscapes in other regions can readily be created.
Fly Through and Animated Movie Files
Terralink’s 3D modelling techniques create a full 3D virtual environment which allows us to animate the camera viewpoints. These animations can be as simple as a panning camera through to recreating a fly through or walk through path. We can animate just the camera over the terrain, or animate objects such as vehicles or water within the 3D model. This data has been used for:
- Public consultation and resource consents
- CD-ROM atlases
- Real estate
- Television documentaries
- Tourism displays
Visit our 3D capability page to view a fly through of Lake Waikaremoana
VRML Data
Our 3D models can be exported into the open source vrml file format to allow real time display in third party software, including web browsers such as Internet Explorer and Netscape Navigator.
Contour Data
Contours of various resolution are derived from digital elevation models and are used in mapping and where a representation of elevations is necessary.
Clutter Data
Clutter data is used to determine interference to the electromagnetic spectrum from transmitter to receiver. This interference comes in many forms and interacts with the mid to upper radio frequency section of the spectrum, reducing the coverage and reliability of communication networks. Our clutter data models contain representations of the surface of the earth, land cover and cultural features in a multidimensional format.
Clutter data analysis enables communications infrastructure providers to accurately predict coverage and audience areas, reduce infrastructure costs by maximizing coverage and enhance the reliability of service and coverage.
To create clutter data models a combination of land cover classifications and building footprints are layered with digital terrain models to provide a 3D model.
For further information on interference, advantages of clutter data, urban and rural classifications and supply formats click here View clutter data sample
Crime Scene Mapping
By reconstructing complex crime scenes and mapping the events and movements of those involved in a three dimensional model Terralink International has assisted the police in their investigations. After a model of a scene is created a number of scenarios can be tested and walk throughs provided to the court in printed form to assist with the presentation of evidence.