3D Perspective Views

3D perspective view of Cape George, Nova ScotiaMost imagery (and/or spatial data) that we view in geomatics is typically viewed vertically downwards from the source toward the map or image. This typical aerial view that we are accustomed to using, allows an abundant amount of information to be represented spatially within a two dimensional cartesian representation. However, occasionally it is useful for us to change our focus from the default traditional view and use a more complex three dimensional visualization view of the data.

This type of terrain model is commonly referred to as a perspective view and often reveals additional information by allowing us to observe the same data obliquely.. In order to do this each location of the image needs to be transformed from the traditional 2-D to a 3-D projection coordinate system.

A perspective view is not really a new tool as it has been around for centuries, but it has become a popular component of most geomatics projects. “A Perspective is a rational demonstration by which experience confirms that the images of all things are transmitted to the eye by pyramidal lines. Those bodies of equal size will make greater or lesser angles in their pyramids according to the different distances between the one and the other. By a pyramid of lines, means those which depart from the superficial edges of bodies and converge over a distance to be drawn together in a single point” (Leonardo da Vinci)¹.

Data integration and overlays are very common with perspective views because it allows traditional flat images to become new products by incorporating an elevation component and providing a new look at the same data. It is also probably used more so for visual appeal then as another method of extracting data.

Sample image on the right is a 3D perspective view of Cape George, Nova Scotia (just north of Antigonish), created with LandSat imagery drapped over a digital elevation model (DEM).

[* quote 1 is from – O’Connor and Robertson (2003) Mathematics and art – perspective www-groups.dcs.st-and.ac.uk/~history/HistTopics/Art.htmlJanuary]

3D Perspective View Samples


3D Perspective View Related Links

LIDAR 3D Surface of Bouctouche, New Brunswick

3D color shaded relief (CSR) digital terrain model (DTM) of Bouctouche, New Brunswick created with LIDAR point data.
LIDAR 3D Surface of Bouctouche, New Brunswick

Gatineau Park Pansharp Fused Image

A pansharpened image fused with a DEM to help provide an extra 3D effect making the topographic features of Gatineau Park stand out more …

Color Shaded Relief Models – Makkovik, Labrador

Color Shaded Relief Models of Makkovik, Labrador Color Shaded Relief Models of Makkovik, Labrador

The above images are color shaded relief models that I created with a DEM of Makkovik, Labrador. These were part of a data integration project that I was involved with during my intense Remote Sensing training at the Center of Geographic Sciences (COGS) in Nova Scotia. the Makkovik region is a coastal area along the eastern coast of northern Canada that is rich with geologic outcrops.

Color Shaded Relief Models – Cap Pele, New Brunswick

Color Shaded Relief Models of Cap Pele, New Brunswick Color Shaded Relief Models of Cap Pele, New Brunswick

The two images above represent artificial three dimensional perspective views perspective views from different points of origin featuring color shaded relief models that were created from high resolution LIDAR digital surface models as part of a LIDAR flood modeling graduate research project.

The study area for the project consisted of the coastal Gulf Shore region of southeastern New Brunswick from Kouchibouguac National Park south to Jourimain Island (location of the Confederation Bridge). The coastal zone of New Brunswick is a picturesque fishing region that boasts several kilometers of sandy beaches with some of the warmest salt water temperatures north of Virginia.

Digital Terrain Modeling – Shaded Relief Models

A shaded relief model uses different color shades according to the varying levels of elevation and azimuth to create an enhanced simulated terrain. The shading is done with the assumption of a defined light source at a fixed location, shone across the surface. The user-specified light source will then determine the positions of shadows and highlighted slopes making ones facing light source appear bright and those facing away appear dark. By default shaded relief models are created with a grey scale ramp that represent the surface reflectance from the light source at any altitude and any azimuth however adding color to it can add an extra chromo stereoscopic component to it.Shaded Relief Model of Lismore, Nova Scotia
Assuming that a straight line is drawn connecting the user defined point source to the top left pixel of the image, the azimuth angle is the aspect of this line in degrees clockwise from north; the elevation angle is the elevation of the line in degrees from the horizontal.

The shaded grey level for each cell is the result of a calculation from the cosine of the angle between the normal vector to the surface (i.e. slope andaspect) and the direction of illumination. All surfaces not illuminated by the light source such as a slope of 90 degrees will be set to 0. An elevation exaggeration is sometimes added to help enhance the features of a fairly homogeneous surface.

In the example shown to the right, a raster aspect map of Lismore, Nova Scotia was derived from a digital elevation model (DEM) calculated with an azimuth angle of 315 degrees and an elevation angle of 45 degrees.

Shaded Relief related:

 

Color Shaded Relief Model of Antigonish Highlands

The large image on the featured as part of this research poster is a color shaded relief model of the Antigonish Highlands in Nova Scotia. The Antigonish Highlands are underlain by a block of older crustal rocks which are bounded and transected by numerous major faults. The Unit stands at an average elevation of …