Gis Revision Part 2

Front 1

What are the three things that a GIS database will contain?

Back 1

A spatial database (.shp), attribte data in attribute tables (.dbf) and a link between them (.shx).

Front 2

What must all map features be coded as?

Back 2

A point, a line or a polygon.

Front 3

What are some examples of point, line and polygon data?

Back 3

Point - drill sites, building locations, animal locations
Line - roads, rivers, flight paths
Polygon - soil types, pollution zones, geological areas, land use, vegetation types

Front 4

What are the two different ways that GIS data can be coded and displayed?

Back 4

Vector and raster

Front 5

Briefly what is vector data?

Back 5

Data in vector format that are stored as lines, points and polygons defined by x,y coords.

Front 6

How does vector coding work?

Back 6

Points - stored as x,y coords
Lines - stored as a series of x,y coords
Polygons - stored as a series of x,y coords with the same starting and ending point

Front 7

What is topology in GIS?
Why is it important?

Back 7

A set of rules that describe how points, lines and polygons share geometry.
Important for many GIS functions: queries and navigation, constructing features from unstructured geometry.

Front 8

What is raster data?

Back 8

Raster features are stored in a regular grid of cells.
Raster data structures are preferred for digital elevation modelling and remotely sensed data.

Front 9

How is raster data stored?

Back 9

Set of cells located by coordinates (y=rows,x=columns) with each cell independently having the value of the attribute.
-Point= a single grid cell
-Line=row of grid cells
-polygon=group of grid cells

Front 10

What are the advantages of raster data?

Back 10

-most common data type
-easy to perform mathematical and overlay operations
-satelite info easily incorporated
-data analysis quick and easy
-easy to overlay

Front 11

What are the limitations of raster data?

Back 11

-cell size determines resolution
-difficult to represent linear features
-cumbersome processing for large amounts of data
-slow display

Front 12

What are the advantages of vector?

Back 12

-graphic output more aesthetically pleasing
-no data conversion required
-geographic location of data remains the same
-more efficient operations
-faster display

Front 13

What are the limitations of vector data?

Back 13

-spatial analysis impossible inside polygons
-each vertex's location needs to be stored explicitly
-manipulative/analysis algorithms are processor intensive

Front 14

How can data be captured from hard copy maps?

Back 14

Scanning, manual digitising - very labour intensive

Front 15

What is metadata?

Back 15

data about the data, how and when it was collected, how it is coded, accuracy etc

Front 16

What is often the selling point for GIS?

Back 16

The quality of display

Front 17

What are some GIS outputs and displays?

Back 17

on screen, printed, on CD/DVD,

Front 18

What are some important map components?

Back 18

Scale, legend, north arrow, title, corporate info and disclaimers

Front 19

What are some decisions that need to be made when planning a GIS?

Back 19

-how should data be coded?
-how should data be managed and stored

Front 20

What is a relational database?

Back 20

Where different but related records can be joined together in a table based on the common fields that they share.

Front 21

What are some different storage paradigms?

Back 21

-geodatabases
-coverages
-shapefiles
-CAD drawings
-Vector datasets
-raster datasets

Front 22

what is a geodatabase?

Back 22

-common data storage frame work for ArcGIS
-combines geo (spatial) data with database (data repository)

Front 23

What are the benefits of using a geodatabase?

Back 23

-optimised performance
-few size limitations
-improved versatility and usability

Front 24

What are shapefiles?

Back 24

-simple data structure
-combines a geo component with an attribute database

Front 25

How are map projections classified?

Back 25

1.By their area/shape distortion
-equivalent (equal area) area is similar on globe and flat map, but shape is not
-conformal - shape (scale) is similar on globe and flat map, but area is not
2.By the shape thay are projected onto
-cylinder, sphere, cone etc

Front 26

Why are cylindrical projections useful and what are some common ones?

Back 26

They are useful for navigation because they are aligned with a compass.
-Peters
-Mercator
-Universal Mercator

Front 27

What is the Lambert Conformal Conic projection?

Back 27

-its on a cone
-preferred projection for regional maps in mid latitudes

Front 28

What is a coordinate system?

Back 28

-A system to represent features in 2d or 3d space
-points are located in reference to a set of intersecting lines
-refered to as "Cartesian coordinates"
-a coordinate system allocates every point on the earth with a series of numbers used to define locations eg latitude and longitude or UTM

Front 29

What are the commonly used coordinate systems (datums) used in Australia?

Back 29

GDA94, AGD66

Front 30

What are the two coordinate systems in GIS

Back 30

1.Geographic - 3D spherical surface to define locations.
Angular unit of measure + prime meridian +datum
latitude and longitude
units are degrees
2.Projected - 2D flat surface based on geographic coordinate system
units are constant and in feet or meters

Front 31

What are some parameters needed for good data management?

Back 31

-UTM zone
-Geographic coordinate system (datum)
-projection
-projection parameters

Front 32

What are 7 geoprocessing tools?

Back 32

buffer
clip
union
erasing
dissolving
extracting
overlay

Front 33

what is the buffer tool?

Back 33

It creates a a set distance around a line/point/polygon as a new polygon layer

Front 34

Whatis the clip tool?

Back 34

removes data from layer A in the shape of layer B and erases anything from layer A that doesn't fit into layer B

Front 35

What does the dissolve tool do?

Back 35

removes unnecessary boundaries.