Geographic Information Systems(GIS)

Geographic Information Systems (GIS)

Tegucigalpa

Capital of Honduras

Population 850,848

landslides and flooding

Online "slippy" maps

Remote Sensing 

Sentinel 2:

S2A (launched 23 June 2015)  and S2B (launched 7 March 2017)

Land use monitoring

Temporal Resolution: Revisit Every 5 days

True Color

Details

From Sentinel 2

Date of image: 22 Feb 2017

Spatial Resolution:

Each pixel represents 20 m

2325 columns

2960 rows of pixels

Sentinel 2

Active Sensor

Passive Sensor

Lidar

1 m resolution! 

Electromagnetic Energy

Features on the Earth reflect, absorb, transmit, and emit electromagnetic energy from the sun.

Properties of electromagnetic energy

Multispectral imagery 

wavelength, fequency, amplitude

The visible spectrum is small! 

What else is collected?

Bands and spectral ranges

Spectral signature

True Color

= Band 4 Red

= Band 3 Green

= Band 2 Blue

False Color Composites

Urban areas

Urban=Purple​

= Band 12 SWIR II

= Band 11 SWIR I

= Band 4 Red

Vegetation

= Band 8 NIR

= Band 4 Blue

= Band 3 Red

Spectral signature

Bands and spectral signatures

Healthy vegetation

Normalized Difference Vegetation Index

NDVI=NIR-IR/NIR+IR

Animation

Possible Assignments - Maps

Can landslides be correlated to land use change?

Future Lessons:

Quantify Change over time between two different images

(atmospheric correction)

Possibilities Classification

Supervised & Unsupervised

Supervised Classifciation - User trains the machine to find what they are looking for specifically

Unsupervised Classifciation -  the machine groups pixels into classes based on spectral signatures alone

Animation

Cloud Computing

• valuable for information dissemination

• faster and more data processing that was not previously possible

• data access

Google Earth Engine

• Cloud-based platform for geospatial analysis

• Access over 40 years of satellite imagery

• Upload own data sets to integrate with publicly available data

• Apply range of common algorithms to data

• Export images, tables, charts, map outputs

Hansen et al (2013)

High-Resolution Global Maps of 21st-Century Forest Cover Change, Science  

15 Nov. Vol. 342, Issue 6160, pp. 850-853 DOI: 10.1126/science.1244693.

Summary

Benefits of CyberGIS

• Data access
• Distributed data processing
• Information dissemination through interactive visualizations

What is the difference between an active and passive sensor? 

What is a spectral signature?

What is a false-color composite?

How are they useful for land use change monitoring?

Spatial and

temporal resolution

What do these terms mean and how are they different?

Name two strengths of CyberGIS and cloud computing? 

Name two different Visualization techniques to show change over time.

Thank you!