Slides Flashcards
Definition of DEM
A digital elevation model is any raster representation of a terrain surface.
Definition of DEM (chart)
Digital Terrain Model:
- point elevation data
- colour shaded relief
- Contour relief
- hillshaded relief
- slope
- aspect
- gradient
Digital Surface Model:
- Terrain features
- vegitation and canopy
- man-made features
Elevation accuracy for 1:50,000 maps
5 and 20m
Canadian DEM (CDEM)
Horizontal Datum - NAD83
Vertical Datum - CGVD28
plotting error is:
0.2mm standard deviation
Types of maps:
general purpose & thematic
purpose of a general map:
locate and navigate
purpose of thematic map:
display by showing the spatial phenomenon or the relationship between several phenomena
Qualitative map:
map the spatial distribution of similar data
Quantitative map:
show spatial variations of the characteristics of a phenomenon
A thematic map should demonstrate:
- likeness of symbols (describing inner relatedness)
- an emphasis on spatial variations
- integrated whole of the map design
A general reference map should demonstrate:
- uniqueness of symbols
- distinction of symbols
- different classes and symbols equally importance
Stages of map design process:
Stage One:
produce general design plan (type of map,size,basic layout)
Stage Two:
produce a specific graphic plan (decide which symbols etc)
Stage Three:
Produce detailed specifications for map construction
Name and describe the SECONDARY Visual Variables
- Pattern Arrangement
- shape and configuration of basic elements - Pattern Orientation
- direction arrangement - Pattern texture
- size and spacing of lines
Name and describe the PRIMARY VISUAL VARIABLES
- Shape
- can be regular or irregular geometric - Size
- length, height, width, area, volume - Orientation
- reference to grid - Colour
- hue (wrt the visible light spectrum)
- Value (lightness/darkness)
- chroma( how close or far away from grey)