Week 3

Question 1

What is geographic data capture?

Answer 1

Collection of geographic information from the real world and representing that digitally in a GIS

Question 2

What are the two types of attributes that you can capture?

Answer 2

Spatial attributes (locations)- geographic data 
Non-spatial attributes

Question 3

What is the five step data collection process

Answer 3

Planning–> preparation (technology infrastructure) –> digitising/ transfer (obtaining image from satellite) –> editing/ improvement (editing/ fixing errors) –> evaluation

Question 4

What are types of data capture methods

Answer 4

Primary
Raster Vector- digital remote sensing images, digital aerial photographs
Vector- GPs measurements

Secondary
Raster vector- scanned maps, DEMs from maps
Vector- Topographic surveys, topomymy (placename) data sets from atlases

Question 5

what are the two types of data capture methods and the difference between them?

Answer 5

In situ data capture- capturing geographic data on the ground by a human being or a specialised data collection instruments - example thermometers.
Examples of in-situ surveying include ground surveying, GPS, (vector), scanning (scanning), digitising, involves direct translation of data into digital form.

Remote sensed data capture- measurement of information of some property of an object by a recording device that is not in physical or intimate contact with he object under study- example satellites, aerial photography, resolution, passive + active

Question 6

Manual digitising

Answer 6

point mode ( direct) versus stream mode (distance)

Question 7

What is remote sensing

Answer 7

g

Question 8

How does GPS work

Answer 8

Known as trilateration ( require 3 satellites to get approximate location, 4 to get an accurate location)

Question 9

What are the 2 types of in situ data capture

Answer 9

Vector data capture

• manual digitising using a digitising table
• manual on-screen digitising
• scanning and vectorisation

Raster data capture
- scanning of maps, aerial photographs

Question 10

Two types of remote sensing data capture

Answer 10

Passive - aerial, landsat, thermal imagery

Active- radar, LiDAR

Question 11

What are the different types of resolution (remote sensing)

Answer 11

Spatial- cell size of raster data sets
Spectral- is the number and size of specific wavelength intervals (referred to as bands or channels) in the electromagnetic spectrum to which a remote sensing instrument is

Temporal- frequency of which the data is collected, temporal resolution is courser

Radiometric- is the sensitivity of a remote sensing detector to differences in signal strength as it records the radi- ant flux reflected, emitted, or back-scattered from the terrain.

Question 12

What is LiDAR and examples

Answer 12

LiDAR- light detection and ranging)

• based on laser and receiver that records return times at points across a swath
• return times allow elevations to be estimated
• high resolution, precision and accuracy

example- DEM and sea-level rise, urban vegetation structure

Question 13

What is georeferencing

Answer 13

• process of connecting a dataset to a coordinate system
• creating control points on the dataset that we know the coordinates of - then the GIS transforms the dataset into the required coordinate system

Question 14

What is the root mean square error

Answer 14

• can be used to assess goodness of fit- to control points but does not measure the non-control point distortion
• measurement of the difference between actual location and predicted location

Question 15

What are the 4 types of measurement error?

Answer 15

Positional accuracy
Attribute accuracy
Logical accuracy
Completeness

Question 16

Positional accuracy

Answer 16

expected difference in the measured geographic location os an entity from its true general position

Question 17

Atrtibute accuracy

Answer 17

the accuracy of the non-spatial attributes of geographic features (i.e. what they are) , example segment name, average daily traffic

Question 18

Logical accuracy

Answer 18

concerned with determining the faithfulness of the data structure of the data set. Such as spatial data inconsistencies- incorrect line intersections, duplicate lines or boundaries, or gaps in lines (spatial errors)

Question 19

Completeness

Answer 19

refers to how complete a data is- consideration of holes in the data, unclassified area, example no data in a chloropleth map

Question 20

Difference between accuracy and precision

Answer 20

accuracy= refers to the extent that both attribute and positional (x,y-location) data correspond to their real-world counterparts.

precision= refers to the “exactness of the measure- ments.”

Question 21

what is meta data

Answer 21

meta data are data about data and should contain information no- how, when, where and who collected the data, scale, coordinate system, data quality and accuracy