Lecture 4 : GIS Data Sources

Question 1

What are the two types of data collection methods?

Answer 1

In-situ data collection

remote sensing of the environment

Question 2

4 examples of in-situ data collection

Answer 2

–GPS
–In-situ land surveying
–In-situ data sampling or census taking
–Digitization of historical spatial information

Question 3

2 examples of remote sensing (RS) of the environment

Answer 3

–Active RS (e.g. LiDAR, RADAR)

–Passive RS (e.g. camera, multispectral and hyperspectral RS, thermal-infrared RS

Question 4

What are the three segments of GPS system?

Answer 4

Space segment
Control segment
User segment (GPS receiver)

Question 5

what is the space segment?

Answer 5

is a segment that consists of a constellation of satellites transmitting radio signals to users.

Question 6

what is the control segment?

Answer 6

A system of tracking stations located around the world

Question 7

what is the user segment?

Answer 7

the GPS receiver and the user community that convert satellite signals into PNT information

Question 8

What is differential GPS (DGPS)?

Answer 8

• A Differential Global Positioning System (DGPS) is an enhancement to the Global Positioning System (GPS) which provides improved location accuracy.
• It is based on two GPS receivers. One is located at a known geographic location while the other is roaming a.k.a roaming GPS receiver. Without DGPS, error goes to 15 metre. With DGPS, error goes down to 10 cm.

Question 9

What is remote sensing

Answer 9

The measurement or acquisition of information of some properties of an object or phenomenon by a recording device that is not in physical or intimate contact with the object or phenomenon under study

Question 10

Visible light is between ____nm to____nm

Answer 10

400nm to 700nm

Question 11

What is an atmospheric window?

Answer 11

an atmospheric window is the portion of the electromagnetic spectrum that can be transmitted through the atmosphere

Question 12

What is a spectral reflectance curve?

Answer 12

A curve that illustrates the reflectance of light from a surface.

Question 13

What do remote sensors do when they are Passive?

Answer 13

The sensors detect the reflectance of sunlight from the object. Eg. CAMERAS

Question 14

What do remote sensors do when they are Active?

Answer 14

The sensor detects the reflectace signal sent by the remote sensing system itself. eg. LiDAR, RADAR, SONAR

Question 15

What is spectral resolution

Answer 15

The number and size of the specific wavelength intervals in the EM spectrum to which a RS system/instrument is sensitive

Question 16

What is spatial resolution?

Answer 16

refers to the size of the smallest feature that can be detected by a satellite sensor or displayed in a satellite image.

Question 17

What is temporal resolution?

Answer 17

Is how often the sensor records imagery of a particular area.

Question 18

What is radiometric resolution?

Answer 18

is the ability of the sensor to distinguish different grey-scale values that are measured in bit