Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Understanding Elements of Remote Sensing
Importance of Mapping Standards
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Talking Points
Talk about current technology
Review remote sensing principles
Discuss importance of mapping standards
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
In the Past: Two flights for two products
Enables one flight for RGBN
Technology Trends
CIRRGB
Film Cameras
Digital Cameras
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Moving into era of higher spatial resolution
Technology Trends
Higher image overlap
• Ultra dense surface models
• Less building lean
More detail than LiDAR
• 5‐cm engineering design
• 3‐inch high value mapping
• 6‐inch urban
• 1‐foot rural
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Technology TrendsSensor Fusion
3D Modeling & Obliques
• Color + LiDAR
• 4‐band + Thermal
• LiDAR + Color, Thermal, Oblique
• Thermal + Hyperspectral
oblique
4‐Band
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Spatial
Temporal
Spectral
Types of Image Resolution
Radiometric
Pixel Size 3‐inch, 6‐inch, 1‐meter
“Bands” blue, green, red, NIR, thermal
Shades of Gray 8‐bit, 12‐bit
Image Frequency monthly, annually, every few years
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Types of Data Accuracy
Lines up in the right area, but not with good repeatability
Seamless, but with a horizontal‐vertical bias
Uniform accuracy and precision throughout dataset
Precision
Accuracy
Consistency
In context of remote sensing
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
What is Infrared Aerial Photography?
400 500 600 700 nm 1100
Color Image
Color Infrared Image
Infrared Imagery is
RED in color
Blue RedGreen Near InfraredNear Infrared
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
RGB = 1, 2, 3
Red
Green
Blue
NIRNIR
2
1
3
4
Layer / Band
Red
Green
Blue
NIRNIR
CIR = 4, 1, 2
Displayed As
Band Combinations
Color
Shift
Red car will ‘look’ greenin CIR mode
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Features of Near‐Infrared
400 500 600 700 nm 1100
ChlorophyllAbsorption
ChlorophyllAbsorption
Biomass Indicator
Refle
ctan
ce
Plant Tissue Structure
Affects the NIR reflectanceThus creating a “signature”
Blue RedGreen Near InfraredNear Infrared
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Near‐Infrared Detects Vegetation
Synthetic Turf“looks real”
Living Vegetation = Red
Color‐Infrared (CIR)Color
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Applications for CIR
• Impervious Surface Area
• Land Cover – Land Use
• Wetland Delineation
• Crop Analyses (precision agriculture)
• Invasive Species (river management)
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Color & CIR
Color
CIR
Vegetation = Red
Water = different signature
Wetland Mapping
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Camera Sensitivity
End ProductMost people use 8‐bit imagery28 = 256 values (0‐255 DN)
Data AcquisitionQuality sensors acquire data at 12‐bits or higher212 = 4096 values (0‐4095 DN)
It is common to optimize 12‐bit data for 8‐bit output
• Enhance detail in shadows
• Reduce effects of haze
• Atmospheric corrections
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Histogram Assessment
NIR Red Green
Typical Bell Curve
Standard Deviations
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Histogram Stretching
Original
Standard Deviation Stretch
Min‐Max Stretch
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Band Combinations
2
1
3
4
Layer / Band Band Combo
Not Used
Not Used
CIR: 4, 1, 2
Mix as Purple• Low vegetation vigor• Non‐vegetation
For Display Purposes Only‐ Does not affect pixel values ‐
False Color: 1, 4, 1
Vegetation as GreenGreenNIRNIR
Red Red
BlueRed
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Band Ratios
NDVI – Normalized Difference Vegetation Index
Red NIRNIR
Red NIRNIR
‐
+NDVI =
‐1 ‐0.5 0 0.5 1Data Range
Indicates Non‐Vegetative Features
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
NDVI
Enhance crop vigor differences within a crop
Research Plots
Real‐World Field
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Mapping Standards
Why they are so Important !
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
“It's unwise to pay too much, but it's worse to pay too little.
When you pay too much, you lose a little money ‐ that's all.
When you pay too little, you sometimes lose everything…”
Business Economics
‐ John Ruskin
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Accuracy = Higher Cost
If project pricing is all over the board
Look at the mapping accuracy being delivered
Unusually low cost often translates into below mapping standards
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Understanding Accuracy Standards
ASPRS
NSSDA
NMAS Era of hard copy, fixed‐scale mapping
Adapted NMAS to account for the dynamic scaling of digital data
Scale‐independent statistical measure
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Understanding Accuracy Standards
ASPRS for 6‐inch GSD orthophotography
RMSe X or Y Radial RMSe
Class III
Class II
Class I
Map Scale1”=100’
1.0‐ft 1.4‐ft
2.0 2.8
3.0 4.2
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Controlling Error
Total Error BudgetRandom Error
0 20 40 60 80 100%
Systematic Error
Sensor Calibration
Position (GPS)Orientation (IMU) Data Processing Interpretation
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Accuracy = Higher Cost
Aerial Photography
Accurate map that always line up in your GIS
New data layers can be generated with confidence
Future data layers will also overlay with accuracy
Has no coordinatesSimply, a pretty picture Photogrammetry
• Ground Control
• Airborne GPS/IMU
• Aerial Triangulation
• Camera Calibration
• Expertise
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Data fusion will only be successful if the spatial accuracy is consistent
Data Accuracy
Avoid having to say . . .• Wish it was better
• Its always been that way
The “low cost approach” can cost more in the long run
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Real Cost of Lower Quality Data
• Re‐do a project from scratch?
• Extensive editing to cleanup data?
• Poor classification results?
What are down stream costs of poor accuracy ?
Quality of your base map (and other layers)
will directly affect your GIS applications
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Don’t “copy & paste” requirements from another proposal
How to procure imagery
• Take the time to understand your needs
• Pretty picture vs. accuracy
Identify your needs
Determine your budget
Gather information from vendors
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Bundling Services can be Counter Productive
Bundling Services
Often a Better Value to use Multiple Vendors
• Adds a middle‐man for communications
• Sometimes more overhead and project cost
• Get to choose best vendor per deliverable
GISObliqueLiDAR
Ortho
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Request Samples
Review Sample Products
Evaluate the Imagery
Highlights / Shadows
Color / Tone Balance
Undesirable Characteristics
Nebraska GIS Symposium ‐ 2013 © 2013 Cornerstone Mapping, Inc.
Multispectral Technology has Numerous Applications
Cornerstone MappingAaron Schepers8118 S 23rd CT
Lincoln, NE 68512(402) 450‐3194
Don’t Forget about Mapping Standards!