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)
Name four different types of visual contrast:
- size
- shape
- colour
- orientation
Name the design principals of figure-ground map organization
- differentiation
-use different colour and texture to seperate figure from ground
2.closed forms and good contours
around lake or island - familiarity
- well known figure needs less emphasis - use of details
- names, city symbols, rivers etc - small size figure
- to emerge while larger areas function as ground
Name and describe the three types of Hierarchical organization.
- Stereogrammic
The use of figure ground principals focus the attention on particular map layers. Usually found in thematic maps - Extensional
showing relative importance of objects in one theme. ex.. road system or a drainage system - Subdivisonal
ex, climate zones, showing different divisions of one theme… aka canada climate zones.
Constraints of Geospatial Reality:
lakes will tend to appear as figures which may be undesirable in a thematic map
complex transportational system
complex extensional
Constraints of available data
old topographic or thematic maps must be georeferenced or digitized.
positional accuracy.
Constraints of Map scale:
Small scale - infer a large viewing
large scale - infer a small viewing section
Constraints of users:
Inexperienced users vs experienced user for symbols
General constraints:
digital maps have to have less fine detailed symbols.
What is visual balance?
The relative positioning of the map components with respect to each other and with respect to the visual center.
What does visual balance depend on?
visual weight
what does visual weight depend on?
position, size, colour, pattern and contrast.
May layout space dimensions?
1.0000:1.618
explain the geomatics design process
use an example. but also include the complex problem, open ended solution(many solutions , choose best), standards(existing, designed, NTS), specific needs
Explain the National Topographic system of canada
A series of maps Basic --> 1:50000 Reconnaissance --> 1:250,000 General reference -- > 1:1,000,000 H/V Datums --> NAD83/CGVD28 UTM false easting of 500000m
