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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

GPS data collection of Jeremys Bay Campground

Poster showing GPS data from Jeremys Bay Campground Kejimkujik National Park and Historic Site, created with ArcMap 9 from data we collected with a Leica RTK GPS & Total Station.

Spatial Database Modeling of forest stands in Kejimkujik National Park

Here is a poster generated with ESRI ArcGIS for a summer GIS project that I worked on for Parks Canada. [The PDF technical report details the methodologies and issues that were encountered with a Spatial GIS vegetation database and GIS Spatial modeling project at the Applied Geomatics Research Group (AGRG) during the summer of 2004 that involved generating a spatial geographic database for Jeremy’s Bay Campground of Kejimkujik National Park and Historic Site. High resolution aerial photography acquired from a previous AGRG (COGS) aerial photography mission was used along with extensive data collected during a Rapid Vegetation Assessment survey and a detailed forest stand interpretation.]

Poster showing Spatial modeling database of forest stands in Kejimkujik National Park and Historic Site

Enhanced LandSAT Images of Trout Lake

The following images are a few enhanced LandSAT images of Trout Lake, Nova Scotia (popular fishing place on the South Mountain – south of the town of Middleton) created using PCI Geomatica.

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.

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:

 

Marathon Canoe World Championships Site Map

The following map was one that I created for the 8th ICF Marathon Canoe World Championships committee depicting the site of the event. This was the first time that the international event took place in Canada and was held in Dartmouth, Nova Scotia in 2000 (Note it is actually a photo of the map I created).

8th ICF Marathon Canoe World Championships Site Map

The ICF Canoe Marathon World Championships are an international canoe marathon event organised by the International Canoe Federation (ICF). The World Championships have been held every two years since their first edition in 1988, before converting into an annual event as of 1998. [source: wikipedia]

Northen Nova Scotia RADARSAT Mosaic

A Northen Nova Scotia RADARSAT mosaic created using PCI OrthoEngine software. Back then RADARSAT data came unformatted and had to be heavily processed and stitched together to form an image like the one featured here …