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Spring 2012 Lab Section:__________________
Prelim Examination # (100 points) 12 March 2012
(1) Topology expresses the spatial relationships between features (points, lines, or polygons) in a digital geospatial database. List and briefly describe the three major spatial relationships expressed and represented by vector-based data models. ( 8 points )
Connectivity: expressing the connection or flow of material within and between features. Containment: defining area of polygonal features Contiguity: expressing adjacency of features
(2) You have two maps, one map has a map scale of 1:24,000 and the other has a map scale of 1:250,000. Your colleague asks to borrow your โsmall-scaleโ map. Which map do you loan to her and why? ( 8 points )
You loan her the 1:250,000 scale map. Small-scale maps represent large land areas but map entities and features are shown in less detail. The ratio, or fraction, of 1/250,000 is a smaller numerical value than the ratio of 1/24,000. Large-scale maps represent small land areas but map entities and features are shown in more detail. The ratio of 1/24,000 is a larger numerical value than the ratio of 1/250,000.
(3) Assuming the elevation in the Ithaca East digital elevation model (DEM) ranges from a minimum of 100 meters to a maximum 700 meters, what is the elevation range per class if you classified the continuous digital elevation model into five equal-interval classes? Indicate below the general form of the raster attribute table that results from this reclassify operation by labeling each attribute (or field) and tabulating data in the appropriate attribute? For which attributes do you have insufficient information to complete the attribute table properly? ( 10 points )
FID Value Count Elev_range 0 1? 100 โ 220 1 2? 220 โ 340 2 3? 340 โ 460 3 4? 460 โ 580 4 5? 580 โ 700
You do not have information related to raster dimension, total number of rasters, or number of rasters per elevation zone in order to complete the โCountโ attribute.
Spring 2012 Lab Section:__________________
(4) List the attribute names that correspond to the type of measurement values (interval/ratio, ordinal, or nominal) that are tabulated below in the feature attribute table. ( 12 points )
Trail Name Attractions Length_km Difficulty Elevation_Gain, m Interloken Lake Vistas 10.5 Easy 75 Backbone Old Growth 5.7 Moderate 200 Gorge Riparian 2.5 Difficult 550 Lakeshore Beach 12.0 Easy 0 Devonian Cliff Fossils 0.5 Extreme 100
Interval/Ratio: Length_km, Elevation_Gain_m Ordinal: Difficulty Nominal: Trail Name, Attractions
(5) Assign geographic coordinates listed below to each of the four corners of a study area and determine the geographic coordinates of the center point (โCPโ) using the following geographic coordinates. List the โXโ coordinate first, then the โYโ coordinate using degrees, minutes, seconds (DMS) in the left two columns and decimal degrees (DD) in the right two columns. Which of the following places is the likely location of this study area: North America, Asia, Australia, or Pacific Ocean? (12pts)
-113o^ 15โ 00โ -115o^ 45โ 00โ -34o^ 30โ 00โ -32o^ 00โ 00โ DMS Decimal Degrees (DD) X Y NW = -115o^ 45โ 00โ -32o^ 00โ 00โ -115.75 -32.
NE = -113o^ 15โ 00โ -32o^ 00โ 00โ -113.25 -32.
SE = -113o^ 15โ 00โ -34o^ 30โ 00โ -113.25 -34.
SW = -115o^ 45โ 00โ -34o^ 30โ 00โ -115.75 -34.
CP = -114o^30 โ 00โ -33o^15 โ 00โ - 114. 50 - 33. 25
Likely location: Pacific Ocean
Spring 2012 Lab Section:__________________
(9) Briefly define the following terms. ( 20 points ) Buffer: Extension or expansion of a spatial feature (point, line, or polygon) or raster by a user-specified distance.
Conformal Projection: A mathematical transformation of 3D space to 2D space that optimizes feature or entity shape while sacrificing to a minimal degree the accuracy of area, distance, and direction.
Developable Surface: A graphical or mathematical construct to transform (or project) a 3-D surface to a 2-D surface. Three types of developable surfaces are used in GIS: cylinder, cone, and plane.
Digitizing: The process of converting analog data to a digital, or computer-compatible, format for manipulation, storage, analysis, and management.
Euclidean Distance: Linear distance between two feature locations, or points, as measured using a Cartesian, or planar, coordinate system with equi-distant scaling on X and Y axes.
False Easting: The numerical value on the axis approximately parallel to lines of latitude defining the zones of projected coordinate systems, such as Universal Transverse Mercator (UTM) and State Plane (SPC) coordinate systems. The eastings are referred to as โfalseโ because the origin of the X- axis is outside the particular UTM or SPC zone where zone-specific numerical values are used.
Orthometric Height: The height of features above mean sea level, or height above the geoidal surface. Orthometic height is equal to the height above the ellipsoid (ellipsoidal height) minus the difference in height between the ellipsoid and the geoid (geoidal height).
Raster Data Model: A geographic spatial representation of real-world entities as grid cells, or rasters, arranged in rows and columns rather than points, lines, or polygons.
Reference Ellipsoid: A mathematical representation of the shape of the Earth as an oblate spheroid, defined using three parameters: semi-major (or equatorial) axis, semi-minor (or polar) axis, and flattening factor (an equation expressing the relationship or ratio of the equatorial axis to the polar axis).
Root Mean Square Error (RMSE): A measure of accuracy in GIS used to quantify the difference (error) between observed, or measured, location(s) and the predicted location(s) of spatial features. The error is squared, the squared errors are summed then divided by the total number of samples to compute the mean of squared errors, then the square root is calculated from the mean of squared errors.
