Imagery Basics: Terms and Acronyms

These photos demonstrate the stark difference between (left) medium and very high resolution.

Field imagery in agriculture has been around for decades. But as the industry stands in “Crop Season 2017,” agriculture still has a ways to go to provide actionable information instead of selling pixels and pictures. Service providers and farmers do not need imagery, they need information — actionable information. They need alerts that tell them there is something that needs to be looked at now — and that there are actions that can be taken to improve profitability. But to get here, the imagery end-user needs to start by understanding what is behind those dots on the page that make up a picture of the farm field.

Understanding Resolution

Resolution is categorized by the pixel size of the remotely sensed imagery. Since the 1972 launch of Landsat by NASA, we know have nearly 1,500 satellites, as well as thousands of airplanes and drones, capturing imagery at different resolutions. Today, we will consider three classes of resolution, as classified by meters (m): Medium Resolution (5 m to 30 m), High Resolution (1 m to 5 m), and Very High Resolution (1 m or better). For agricultural applications, there are a wide range of platforms providing imagery at multiple resolutions and frequency at the global and local scale. The following sections will discuss the sensors and sources of various satellite, aerial, and UAV platforms.

Why does resolution matter? It depends on what is your need. It’s all about aligning the correct information for your problem.

Medium Resolution Imagery (5-30 meters)

NASA’s Landsat is a fantastic sensor that’s been imaging the planet for decades. At 15-meter resolution, it is best used to identify landscape scale change; example uses are zone and drainage plans. Between Landsat 7 and Landsat 8, a new image of the entire planet is taken every eight days. For paid imagery, we have RapidEye at 6.5-meter which is now owned by Planet Labs.

High Resolution Imagery (1-5 meters)

Companies such as Planet Labs and Skybox (now Google) are launching fleets of micro satellites or small sats, with a vision to make imagery cheap, frequent and accessible. They plan to revisit a given place on the globe multiple times a day. While these micro satellites are designed for a short life of 3 years or less, they can take advantage of changes in new sensors. Further, the constellation approach of medium resolution satellites offers a unique revisit for broad crop monitoring area on a daily basis.

Very High Resolution Imagery (< 1 meter) Queue the Airplanes and Drones

This imagery range has been the domain of the airplane imagery provider — and over the last 3 years — drone providers. This imagery is ideally suited to identify and address in-field, in-season agriculture problems.

There are quite a number of airplane and drone imagery providers focused on the agriculture industry. The greatest advantage is that airplanes and drones are able to collect information for specific fields at specific times in the growing season. Part of the challenge is overall inconsistency in the process, which includes the following: no standard type of cameras are used; the quality of pilots or drone operators is variable; and how fast and well the imagery is processed and presented in order to inform the grower or adviser on what to do next.

Another source of very high resolution imagery is the smartphone and tablet. They can take very detailed pictures of plants, bugs, soil and more. Smartphones enabled with personal navigation can be used to cue humans to very specific locations to then capture sub-millimeter color imagery. Smartphone imagery can then be sent to experts and machines for interpretation and diagnosis.

Terminology Alphabet Soup

One of the symptoms of a maturing, competitive industry (and one of its biggest frustrations) is the evolving, swirling, confusing stew of terms and acronyms used to describe differences in technologies and offerings. Imagery terms NIR, VI, UV, TIR, SIR and NDVI (among several more) use to identify and explain the variations of imagery, but do little to help end-users decide what will work in their particular applications.

In a perfect world the industry would evolve to simpler, easier to understand designations and end the TLA (three-letter acronym) madness. What service providers and farmers care about is that when they review the imagery, will it tell them something?

Someday the industry will arrive at that point. In the meantime, these are some of the most common terms in imagery and their meanings and common uses.

  • GSD – Ground Sampling Distance or pixel size of the remotely sensed imagery. Example: 30-meter; 1-meter; 20-centimeters.
  • NDVI – Normalized Difference Vegetation Index is the ratio of the difference between the red and near-infrared bands divided by their sum used to identify and enhance the vegetation contribution in a digital remote sensing analysis.
  • VI – Vegetation Index, is a ratio created by dividing the red by the near-infrared spectral bands used to identify and enhance the vegetation contribution in a digital remote sensing analysis.
  • VRT – Variable-Rate Technology, refers to a system that varies the rate of agricultural inputs such as seed, fertilizer, and crop protection chemicals in response to changing local conditions.
  • TIR – Thermal Infrared is shown in gray tones to illustrate temperature. It measures radiation from the plant and soil surface.
  • NIR – Near infrared (red), green (blue), red (green) is useful in seeing changes in plant health.
  • SIR – Shortwave infrared (red), near infrared (green), and green (blue) used to show flooding or newly burned land.
  • Yield Mapping – refers to the process of collecting geo-referenced data on crop yield and characteristics, such as moisture content, while the crop is being harvested.

Leave a Reply

Imagery/Sensing Stories
Satshot imagery
Imagery/SensingImagery in Agriculture: Some Sage Advice
August 6, 2017
SatShot President Lanny Faleide has been a fixture on the remote imagery scene for as long as about anyone still Read More
Imagery/SensingSpecial Report: Imagery in Row Crop Agriculture
August 3, 2017
It starts with Big Maps, Google Earth, and GPS on iPhones and Androids. But it’s the combination of easy access Read More
Imagery/SensingImagery: Inside The Spectrum
August 2, 2017
Camouflage photography, developed during World War II, opened the era of remotely sensed images and the possibility of seeing more Read More
Imagery/SensingImagery: Show Me the Money
August 2, 2017
As you have seen throughout this report, aerial imagery has been a “thing” in agriculture for decades. Systems and delivery Read More
Trending Articles
Business ManagementBringing a Southern Sensibility to Precision Agriculture
August 7, 2017
Amy Winstead considers herself blessed to have gotten in on the ground floor of precision ag adoption in the Southeast. Read More
Sensors/IoT2017 Yield Monitor Calibration Checklist — Part I
August 4, 2017
With fall harvest a few weeks away for most of the country, ag service providers from every walk of life Read More
Excellence AwardsBuilt By Agronomists: 2017 Award Of Excellence Winner Wade Barnes on the Making of Farmers Edge
August 2, 2017
Farmers Edge President And CEO Wade Barnes reflects on the process of building his company, shortly after receiving the Crop Adviser/Entrepreneur Award during the InfoAg Conference in July. Read More
Data ManagementInfoAg 2017 Recap: Service Providers Take Center Stage
July 28, 2017
As I sit here and ponder just what it was that we all experienced last week, off the top of Read More
InternationalUsing Precision Agriculture to Control Herbicide-Resistant Weeds in Brazil
July 24, 2017
The occurrence of weeds in agricultural fields of grain and fiber production has caused losses to farmers for a long Read More
Yield Data Image
Data ManagementYield Data: More Than a Pretty Picture
July 13, 2017
It is mid-July, which, for the Australian cotton industry, means that picking is still going on for some growers. A Read More
Latest News
InternationalIsraeli Precision Ag Companies Lead in Water Use Effici…
August 16, 2017
In the last week, AgriHub, formed by farmers and consultants from Brazil, visited 10 Israeli agribusiness companies, including the Ministry Read More
ProfessionalsMechanization Key to the Future of Vineyard Management
August 15, 2017
Precision technology moves at different speeds across different segments of agriculture. For example, technologies like curve compensation, precision spraying, and Read More
Data ManagementSignificant Updates Made to SoilWeb, Web Soil Survey Pr…
August 15, 2017
Agronomic professionals and technicians dealing with precision farming must understand the soils within the field before writing effective prescriptions.  A Read More
Business ManagementOpinion: How to Leverage Precision Agriculture to Launc…
August 14, 2017
To continue where my last article left off (which you can check out here), a precision ag company that specializes Read More
Industry NewsFarm Dog Inks Non-Funded Cooperative Agreement with USD…
August 14, 2017
Farm Dog, a pest and disease management platform for growers and agronomists, has entered into a Non-Funded Cooperative Agreement (NFCA) Read More
InternationalAgtech: What the Umbrella Term Really Means
August 10, 2017
Acclerator, incubator, start-up, connectivity — the buzzwords of the digital age can be clear as, well, mud, writes Alex Sampson Read More
Spray Drift
Data ManagementJanzen: Data to Play Key Role in Sorting Out Dicamba Di…
August 10, 2017
You would have to live under a rock to not have heard about farmers’ issues with dicamba this growing season. Read More
InternationalNew Zealand Study Tour to Demonstrate Recent Advances i…
August 10, 2017
If you’re interested in an intense, week-long immersion in the use of high-tech products and practices in New Zealand agriculture, Read More
Data ManagementDuPont Acquires Ag Tech Startup Granular for $300 Milli…
August 9, 2017
DuPont announced that it has signed a definitive agreement to acquire San Francisco-based Granular, Inc., a provider of software and Read More
EventsSDSU Prof to lead Profit-Focused Panel at Upcoming Inno…
August 9, 2017
Convening a day prior to this summer’s Farm Progress Show at the I Hotel in Champaign, IL (about an hour’s Read More
AGCO White planter 9800VE
ProfessionalsAGCO Crop Tour 2017 Features Precision Planting Add-Ons
August 8, 2017
Higher yields and greater returns are the ultimate goals for crop producers. To help corn growers better understand the role Read More
Business ManagementCrop Pro Insurance Closes $8 Million in Series A Fundin…
August 8, 2017
Crop Pro Insurance today announced the close of an $8 million Series A round of financing co-led by top agriculture Read More
Business ManagementBringing a Southern Sensibility to Precision Agricultur…
August 7, 2017
Amy Winstead considers herself blessed to have gotten in on the ground floor of precision ag adoption in the Southeast. Read More
Satshot imagery
Imagery/SensingImagery in Agriculture: Some Sage Advice
August 6, 2017
SatShot President Lanny Faleide has been a fixture on the remote imagery scene for as long as about anyone still Read More
ProfessionalsHow Blue River’s See & Spray Technology Could Chang…
August 5, 2017
The blistering West Texas heat rocketing towards triple digits, the affable cotton grower trudged across his dusty field and approached Read More
Grower Services & Solutions2017 Yield Monitor Calibration Checklist — Part II
August 4, 2017
(EDITOR’S NOTE: This is Part II of Tim Norris’ Yield Monitor Calibration checklist, Part I of which was published in Read More
Sensors/IoT2017 Yield Monitor Calibration Checklist — Part I
August 4, 2017
With fall harvest a few weeks away for most of the country, ag service providers from every walk of life Read More
ProfessionalsSoil Sampling in 2017: Data Driven
August 4, 2017
Generally speaking, any ag service provider’s most important job is to help grower-customers produce more with less. According to Jill Read More