lecture 4

Question 1

what does geographic data refer to?

Answer 1

locations on earths surface or locations relative to the earths surface

Question 2

what does spatial data refer to?

Answer 2

any locational frame or reference

Question 3

what are the two types of geospatial features?

Answer 3

spatially continuous or spatially discreet

Question 4

what are fields?

Answer 4

continuous variables; a feature that occurs everywhere eg. height, topography

Question 5

what are some characteristics of spatially continuous features?

Answer 5

occurs everywhere, sometimes called fields, measurement anywhere in the domain.

Question 6

what are some characteristics of spatially discreet features?

Answer 6

distinct spatial extent (boundaries/framework for feature), attributes only within the extent, sometimes called entities or objects (buildings, roads, rivers)

Question 7

What are the ways discreet data can be represented in GIS?

Answer 7

grid, polygon, point, polyline

Question 8

describe point features

Answer 8

single point, used to define single, identifiable locations on the earths surface (could be a point in a tree, in grass, on a building); single X, Y (cartesian coordinate)

Question 9

describe polyline features

Answer 9

joined points, think things like roads, rivers, boundaries; two cartesian coordinates, start and end with nodes points

Question 10

describe polygon features

Answer 10

looped/bounded by line area; think things like lakes, forests; closed loop of cartesian coordinates; start and end with node points, mostly simple in GIS so cannot overlap

Question 11

describe grid features

Answer 11

represented as cells/pixels, in rows and columns, covering a spatial extent; think things like elevation, land cover, temperature. also images. rastewr format allows or

Question 12

what is important to remember about line segments in vector data models?

Answer 12

even thought they may look smooth at lower scales, all line segments are straight

Question 13

what is the benefit of using vector data models to store geospatial locations?

Answer 13

efficient as represents only the necessary points and connections.

Question 14

what does topology refer to in spatial analysis?

Answer 14

spatial relationships between features; adjacency, touching, dis-jointness.

Question 15

benefit of understanding topology?

Answer 15

allows for spatial queries/searches, which helps to identify specific things (connectivity of features like roads etc.)

Question 16

why should polygons in vector data not overlap?

Answer 16

violates the Euclidean geometry principles; can lead to errors in spatial analysis. GIS normally has checks to prevent.

Question 17

what are vector data models better at representating?

Answer 17

discreet data, so suitable for spatial analysis tasks

Question 18

raster data models are suitable for what?

Answer 18

gridded data, satellite images/national land cover datasets

Question 19

what can raster data represent?

Answer 19

continuous variables (elevation eg.) and categorical variables (land cover types eg.)

Question 20

when is raster data memory intensive?

Answer 20

when very high resolution

Question 21

how do nominal raster data sets work?

Answer 21

of categorical data, values represent different categories, but values do not have numerical meaning/order.

Question 22

how do ordinal raster data sets work?

Answer 22

of categorical data, represent categories that can be ordered. the differences between medium, eg, and small may not be the same as between medium and large though.

Question 23

how are different categories represented in discreet data encoding?

Answer 23

using specific values/codes

Question 24

is each pixel specified in a raster grid?

Answer 24

yes; each pixel is associated with one discreet value which will correspond to a distinct feature/characteristic.

Question 25

what is discreet data encoding usually used for?

Answer 25

raster data analysis; land cover mapping, terrain analysis, habitat classification. helps analyses categorical information, spatially.