1 / 50

Information Representation

Information Representation. Imagery Terrain Thematic Maps. Imagery.

joshwa
Download Presentation

Information Representation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Information Representation • Imagery • Terrain • Thematic Maps

  2. Imagery • Of the three types of maps discussed (image maps, physical models and line maps) image maps come closest to depicting the environment in the way we see it. Image maps are derived from systems that capture the a image of an entire region with all its "visible" details. The types of imaging systems are photographic systems, electronic sweep scanners and digital arrays.

  3. Imagery • Photography is • The process of collecting / recording images on asensitized surface (e.g. film)by the action of light or other radiant energy. • A Photograph is the resultant Negative or Positive

  4. Photography Example

  5. Imagery • Imaging is • The mapping of the intensity of radiation reachinga sensoras a function of position in a 1-D or 2-D field • Either on film, in a computer, on a CRT screen, orother display device. • An ‘image’ is the resultantmap.

  6. Imaging Example

  7. Imaging Example

  8. Imagery • Photo Interpretation • The act of examining aerial photographs orimages for the purpose of identifyingobjects & judging their significance • Photogrammetry • The science of obtaining reliablemeasurements by means of photography.

  9. Uses of Remotely Sensed Data • Background Images for GIS Overlays • Monitor Changes • Extract Infrastructure Information • Roads, Structures, etc • Disaster Effects • Extract Land Cover Information • Vegetation Cover • Water Sources Imagery

  10. Imagery Uses

  11. Imagery Uses

  12. Imagery   Image vantage points are horizontal, oblique and vertical

  13. Horizontal • This is the way we see the world. Capturing images from this vantage is problematic because of the limited area that can be seen and the variable scale associated with this vantage point.

  14. Oblique • High oblique image are taken with the sensor inclined between 0 and 45 degrees to the horizon. The horizon is visible in a high oblique photograph. A low oblique photograph has a sensor incline between 45 and 90 degrees to the horizon. Scale for both of these images decreases from the foreground to the background.

  15. Vertical • These are the most common type of images taken for inventory and mapping purposes. The sensor is perpendicular to the earth's surface. The greatest advantage of this type of image is that scale is relatively constant, and the block of features is minimized.

  16. Geometric Corrections • Images have inherent distortions due to the imaging geometry of the sensor system. Photographic systems have distortions due to the perspective geometry of the photographic system and the camera orientation at the time the image is collected. These distortions have been mathematically modeled and can be corrected to produce orthophotography, a map-like image.

  17. Terrain • Terrain is a critical aspect of our environment that limits the possible uses to which we can make of the land. Its portrayal on maps can take may forms.  

  18. Data for Terrain Mapping and Analysis • A Digital Elevation Model (DEM), consists of a sampled array of elevations for ground positions that are normally at regularly spaced intervals.

  19. DEM Example

  20. Data for Terrain Mapping and Analysis • Triangulated Irregular Network (TIN) • Series of non-overlapping triangles • Elevation values are stored at nodes • Irregular distribution • Sources: DEMs, surveyed elevation points, contour lines, and breaklines • Breaklines are line features that represent changes of the land surface such as streams, shorelines, ridges, and roads

  21. Data for Terrain Mapping and Analysis • Triangulated Irregular Network (TIN) • Not every point in DEM is used • Only points most important • VIP (Very Important Points) algorithm • Maximum z-tolerance algorithm • Delaunay triangulation: all nodes are connected to their nearest neighbor to form triangles which are as equi-angular as possible. • Borders are a problem • Go beyond study area and clip to make best

  22. TIN Example

  23. Terrain Mapping • Contouring is most common method for terrain mapping • Contour lines connect points of equal elevation (isolines) • Contour intervals represent the vertical distance between contour lines. • Arrangement of contour lines reflect topography

  24. Contour Example

  25. Terrain Mapping • Vertical profile shows changes in elevation along a line, such as a hiking trail, road or stream.

  26. Terrain Mapping • Hill shading is also known as a shaded relief or simply shading • Attempts to simulate how the terrain looks with the interaction between sunlight and surface features. • Helps viewers recognize the shape of land-form features on a map.

  27. Hillshading Example

  28. Hillshading • Four factors control the visual effect of hill-shading • Sun’s azimuth is direction of incoming light (0 to 360°) • The sun’s altitude from horizon (0-90°) • Surface slope (0-90°) • Surface aspect (0 to 360°)

  29. Terrain Mapping • Hypsometric tinting • Applies different color symbols to represent elevation zones.

  30. Terrain Mapping • Perspective View • Perspectives are 3-D views of the terrain wherein the appearance is as viewed from an airplane. • Viewing azimuth (0 to 360°) • Viewing angle (0-90°) • Viewing distance • Z-scale is ratio between he vertical scale and the horizontal scale (exaggeration factor) • 3-D draping of vector information

  31. Thematic Maps • Planimetric maps • Attribute maps focus on the locations of specific environmental features or attributes such as highways, towns, parks and rivers . • Distribution/Statistical maps focus on the spatial variation of environmental features or themes.

  32. Attribute Maps • Single-variable symbols: symbols that represent one kind of feature. Graphic elements used to communicate the qualitative aspects of the features are: shape, pattern arrangement, pattern orientation and color hue. (note: size, texture, color value or color intensity are reserved for quantitative representation.)

  33. Single Symbol Variables • Point emphasis • Identifies a feature at a specific location. Qualitative feature are usually represented by pictographic or geometric point symbols.

  34. Pictograph Example

  35. Geometric Shape Example

  36. Single Symbol Variables • Line emphasis: symbols that have obvious length and width. Form is the usual graphic element used to distinguish line features.

  37. Single Symbol Variables • Area emphasis: map makers use hue, arrangement and orientation to distinguish area qualities. The use of visual elements that indicate magnitude such as intensity, texture or size are confusing when applied to qualitative data and should not be used.

  38. Attribute Maps • Multivariate symbols: usually map makers use separate symbols for each variable. At times however multiple variables are represented. By varying symbol shape, hue, texture and arrangement map makers could show four variables at once. However,  no more than two variables are usually represented.

  39. Multiple Variables • Point emphasis: • 2 variables are often represented by combining shape and hue.

  40. Multiple Variables • Line emphasis • less useful because of the extent of the linear feature. Some examples are scenic routes and construction delays.

  41. Multiple Variables • Area emphasis: multiple variables can be shown by overlapping regions or by combining pattern with color.

  42. Cartograms • Area or distance are distorted to portray value

  43. Cartogram Example

  44. Statistical maps • Statistical maps use quantitative symbols to depict magnitude information. The graphic elements for doing this are size, pattern texture, color value and color intensity.

  45. Statistical maps • Single Variable: to show quantitative information symbols are varied to show changes in magnitude. These symbols can be either pictographic or geometric.

  46. Statistical maps • Point emphasis • Pictographic symbols usually vary only in size where as geometric symbols vary in texture, color value and color intensity as well as size. Creating apparent magnitude scaling of size and density compensation makes some accommodation of the limits of human perception.

  47. Statistical maps • Line emphasis • Cartographers use proportional line symbols to show changes in magnitude. One of the most common is line thickness.

  48. Statistical maps • Area emphasis • 2-D (Choropleth) • These maps show both area and magnitude. • 3-D maps • Three types of maps are the region bounded map, the perspective profile and the continuous surface shading. While effective, the exact height at any given point is hard to determine. 

  49. Choropleth Example

  50. Statistical maps • Multivariate symbols: showing several variables with the same symbol. Size is often used to represent multiple variables. Symbology can get complex and requires creativity. • Pie Charts • Bivariate Legends

More Related