r. khosla / l. longchamps 2015 1 - colorado state university

9/23/2015

R. Khosla / L. Longchamps 2015 1

Introduction toRemote Sensing

Overview

What is remote sensing

Types of remote sensing– Photography

Fundamentals

Scale

Terminology

Georeferencing

Interpretation

Electromagnetic spectrum

Resolution

Advantages of Remote Sensing

http://www.aero.org/publications/crosslink/winter2008/03.html

What is Remote Sensing?

Collecting information about an object of interest (e.g. farm field) without being in contact with the object

Examples:

– Human sight

– Photograph

– Radar

9/23/2015


Types of Remote Sensing

Passive Remote Sensing

– Relies on Sun’s Energy

– Records Response to Sun’s Energy

Active Remote Sensing

– Has it’s Own Energy Source

– Records Response of an Object to this Energy

Clowes

Types of Remote Sensing…

Human eyes

Radar/Sonar

Electromagnetic Induction

Satellite Imagery

Greenseeker

Induced Fluorescence

Photography

Active Passive

Photography: Passive vs Active

Without flash With flash

Passive Active

9/23/2015


Despite all satellites and sensor systems, photographyremains the most practical, inexpensive, and widelyused means of remote sensing in use today!

Understanding of photography is KEY tounderstanding other remote sensing procedures

Photography

In remote sensing, most attention is directed towards photographs taken above the earth’s surface

– This is termed Aerial Photography

– Aerial photos are taken with special cameras called Framing Cameras

Fundamentals of Photography

Framing Cameras

Fundamentals…

http://www.specialised-imaging.com/img/photo/tue1052.jpg

http://www.jdaviation.us/camera.html

http://www.macsimage.com.au/

9/23/2015


Charge Coupled Device (CCD)

6.54 μm

5.6 μm

Framing camera96 x 88 mm8448 mm2

http://www.ipi.uni-hannover.de/uploads/tx_tkpublikationen/2011_GISOSTRAVA_KJ.pdf

Z/I DMC IIe 250 Frame Camera

1/3”4.80 x 3.60 mm

17.30 mm2


Samsung Galaxy S4 Apple iPhone 5

Phone Width (mm)

Height (mm)

MPPixel size

(mm2)

S Galaxy S4 6.17 4.55 16 0.18 x10-6

A iPhone5 4.54 3.42 8 1.94 x 10-6

Which one is better for details and digital zoom?Which one is better for indoor (darker) scenes?

m

Image sensor

Why more green pixels?

Red Green Blue

RGB


Color filter array

Sensor

Filter

9/23/2015


Image sensor


Color filter array

Photograph Terminology

• SCALE- is the relationship between a linear distance on a photograph and the corresponding ground distance

• Example- scale = 1:24000, so 1 inch on the photo is equivalent to 24,000 inches on the ground

Fundamentals of photography…

Scale

Small vs. Large-Scale photography

– In a small-scale photo everything looks small

– In a large-scale photo everything looks large

Question: 1:24,000 or 1:250,000

Which is a smaller scale?

Answer - 1:250,000

Fundamentals…

Scale

9/23/2015


Small-Scale

Fort Collins, CO

1:250,000

Large-Scale

Fort Collins, CO

1:24,000

Scale

Fundamentals of photography…

Same idea with models

1:24TH SCALE

9/23/2015


Photography scale is dependent upon the following

– Camera focal length (f)

– Flying height above the ground (H)

– Scale = f/H

– Note: units must be the same!

Fundamentals…

Lens

CCD

Scene

Focal length (f)

Scale = f/HPhotography by Jim R Harris

Height (H)

Scale example:

– Flying height = 10,000 ft above the ground

– Focal length = 6 in (very common)

Scale = 0.5ft / 10,000ft = 20,000

– Scale of the photo is 1:20,000

Note: if we did not use the same units (ft), our scale would be way off

Fundamentals…

9/23/2015


Terminology

– Nadir- Is the point on the photo that is directly beneath the center of the camera lens

– It is not always the center of the photograph

– As it pertains to photos, a Nadir-view photo is one in which the camera is directly above the scene

Fundamentals…

Oblique- The scene is captured while the camera is at an angle

Nadir (vertical) view Oblique view

Camera lensTiltedNo tilt

Fundamentals…

Fundamentals…

Nadir View

Plant Sciences Building

Oblique View

Plant Sciences Building

9/23/2015


Nadir

– Little distortion

– More accurate measurements

– Allows stereo-viewing

Oblique

– Captures larger scene

– Better for some applications (early crop development)

– Similar to human eye’s view from an airplane

Fundamentals…

Nadir-view Oblique-view

Early Crop Development

Fundamentals…

Terminology

– Displacement- The apparent shift in the location of an object with respect to its “real” location on the ground- displacement is what allows stereo-viewing

– Distortion- Is a change in the shape of an object due to the curvature of the camera lens and the earth’s surface

Fundamentals…

9/23/2015


Georeferencing

Missing spatial reference

What am I doing in Africa?(0.000000; 0.000000)

Georeferencing

Roughly provide Coordinates of to left corner of raster

9/23/2015


Georeferencing

Georeferencing

Georeferencing

9/23/2015


Aerial photo interpretationrelies on the following

• Shape

• Size

• Pattern

• Texture

• Association

• Tone

Low

Low

LowLow

High

High

Medium

Medium

Medium

Medium

Low

R: 145G: 206B: 23

R: 112G: 39B: 28

Smooth

Rough

Intermediate

Fundamentals…


Infra-red

Microwave

Radio wave UV Gamma rays

X rays


Infra-red

Microwave


X rays

9/23/2015


http://stratus.astr.ucl.ac.be/textbook/chapter2_node3.xml

Figure 2.1: Spectrum of the energy received from the Sun and emitted by the Earth at the top of the atmosphere. Figure from Y. Kushnir available at: http://www.ldeo.columbia.edu/~kushnir/MPA-ENVP/Climate/lectures/energy/

B, G, RThe visible portion of the spectrum

Blue ~400-500nm

Green ~500-600nm

Red ~600-700nm

The visible portion of the spectrum

Blue ~400-500nm

Green ~500-600nm

Red ~600-700nm

• Most of the sun’s energy is received between 400 and 700nm• Portion of the spectrum visible to human eyes• Why more green sensors?



Blue ~400-500nm

Green ~500-600nm

Red ~600-700nm


Blue ~400-500nm

Green ~500-600nm

Red ~600-700nm


Three bands Red, Green and Blue

The infrared portion of the spectrum (IR) 720 - 15000 nm

– Near-infrared (NIR) = 720 – 1500 nm

Photographic IR = 720 - 900 nm

– Middle-infrared (MIR) = 1500 - 5600nm

– Far-infrared (FIR) = 5600 - 10000 nm a.k.a. thermal IR


9/23/2015


As wavelengths become shorter, the energy increases


Hit target at higher speed


Infra-red

Microwave


X rays

Which band delivers more energy?

The energy balance can be written as an equation

I = A + T + R

– I = incoming solar energy

– A = absorbed energy

– T = transmitted energy

– R = reflected energy

Reflected energy is the most important for remote sensing purposes

Energy Balance

9/23/2015


Basically, three things can happen to solar energy

1) it can be absorbed and dissipated as:

1) Heat

2) Photosynthesis

3) Fluorescence

2) it can be transmitted

3) it can be reflected

Energy Balance

Three Types

– Temporal

– Spectral

– Spatial

Resolution

What is Temporal Resolution?

Temporal Resolution is all about time (i.e., frequency at which data is collected)

– Which set of imagery has a higher temporal resolution?

– Farm field image collected every 16 days (Landsat) or collected every 2 days (MODIS)?

Resolution…

9/23/2015


What is spectral resolution?

Spectral resolution depends on how many wavebands were acquired in a particular area.

Resolution…

Color Photo only has info in 3 bands (Visible)

Resolution…

Red channel Green channel Blue channel

Resolution…

Landsat 7 has 7 bands:

1. Blue-green

2. Green

3. Red

4. Near-infrared

5. Mid-infrared

6. Thermal-infrared

7. Mid-infrared

0.4 μm 0.5 μm 0.6 μm 0.7 μm 0.8 μm 1.5 μm 2.0 μm 2.5 μm 10 μm 11 μm 12 μm

VisibleUltraviolet

(UV) Near-IR Mid-IR Thermal-IR

9/23/2015


OR

Which image has higher spectral resolution?

Resolution…

Digital Camera

What is spatial resolution?

Spatial resolution is similar to scale

Spatial resolution is basically pixel size

Example: Landsat 8 has a resolution of 15m while WorldView 3 has 0.31-m resolution (Pan).

Which one has higher resolution?

Resolution…

Resolution…Each square (pixel) is

30 X 30 meters

9/23/2015


Comparing resolutions

Satellite LunchedSpatial

(m)Temporal

Revisit/True NADIR (days)Spectral (bands)

Ikonos 1999 0.82 4 / 144 4

Quickbird II 2001 0.61 4.2 / NA 5

WorldView-1 2007 0.41 2.4 / NA 1 Pan

GeoEye-1 2008 0.41 3 / NA 5

RapidEye 2008 6.5 1 / 5.5 5

WorldView-2 2009 0.46 1.1 / NA 9

Pléiades 1-2 2012 0.5 1 / NA 5

WorldView-3 2014 0.31 <1 / NA 16

Landsat 8 2013 30 16 / 16 11

Spectral Signatures

Different materials reflect energy differently at various wavelengths

This is the basis for much of what we do in remote sensing and agriculture

Lets look at some examples...

Signatures…

R, G, B

R = 245G = 149B = 56

R = 122G = 168B = 85

R = 73G = 117B = 88

R = 99G = 128B = 106

9/23/2015


Spectral signature of green plantsSignatures…

Per

cent

Abs

orpt

ion

High green reflectance High IR

reflectance

High blue and red absorption

Plant look dark, light mostly absorbed in Visible spectrum

Plant look bright, light mostly reflectedin NIR

Signatures…

http://missionscience.nasa.gov/ems/08_nearinfraredwaves.html

Signatures…

Source: Wulder, M. A., Dymond, C. C., White, J. C., Leckie, D. G., & Carroll, A. L. (2006). Surveying mountain pine beetle damage of forests: A review of remote sensing opportunities. Forest Ecology and Management, 221(1), 27-41.

9/23/2015


Bare Soil

Growing Crop

Wetland/Riparian Area

Signatures…

6 /08 7/08 8/03 9/12

Do Signatures Change?Signatures…

Landsat

Began in 1972

Instrumentation

– Multispectral Scanner (MSS: 4-band)

– TM (thematic mapper)

Characteristics

– Polar orbital

– 16-day cycle

– Altitude = 705km

Systems

Landsat 1, 1972

9/23/2015


Landsat

Characteristics– Near global coverage

– 30-m resolution

Landsat 8 started May 2013– 11 bands

Systems…


1. Violet NEW2. Blue3. Green4. Red5. NIR6. Shortwave IR (SWIR1)

7. SWIR28. Panchromatic (all

visible spectrum)9. 1370 nm (clouds) NEW10. Thermal IR (TIR1)11. TIR2 NEW

Landsat 8

Characteristics– Near global coverage

– 30-m resolution

Systems…


Landsat 8 : 11 bands

Operational Land Imager (OLI)

Thermal Infrared Sensor (TIRS)

WorldView-3

Instrumentation

– 8-band multispectral scanner

– 8-Shortwave IR (SWIR)

Characteristics

– Altitude = 617 km

– <1-day cycle

– Global Coverage

– Resolution

0.50m panchromatic

2.0m multi-spectral

Systems…

9/23/2015


WorldView-3

What is Panchromatic?

RGB composite (5 m) Panchromatic (2 m) Pan-sharpened RGB (2 m)

Band 1 Band 2 Band 3 Band 4

Panchromatic

How Does This Technology Help

Farmers?

How Does This Technology Help

Farmers?

9/23/2015


Advantages of Remote Sensing

Inaccessible areas

Large geographic areas

Multiple wavelengths

Permanent record

Data collection is rapid and economical

Multiple uses

http://www.resourcemappinggis.com/land_estimating.html

Benefits to Farmers

Sampling

Identify problem areas

– weeds

– pest damage

http://www.precision-crop-protection.uni-bonn.de/gk_research/project.php?project=2_01

http://ces.ca.uky.edu/pendleton/AG_SoilSamples

http://foodtrust.wordpress.com/2007/09/13/the-robinson-farm-and-integrated-pest-management/

Which system is most useful for precision Ag? (WorldView or Landsat)

WorldView Imagery is probably most useful

Why?

9/23/2015


Area = 18.5 ha, = 185000 m2

What would the difference be between a Landsat and a WorldView image?

At 30-m resolution from Landsat image would give us 205 pixels

At 0.31-m resolution, a WorldView image would give us 1,925,078 pixels

9/23/2015


Landsat 8 WorldView-3

What is this?

Reentry capsule (nicknamed "film bucket")

We are in 1959

CCD was invented in 1969

Corona program 1959-1972

r. khosla / l. longchamps 2015 1 - colorado state university

Documents