Crop Scouting with Aerial Imagery – Choosing the Right Source

June 2, 2021 3:46 PM
Blog Post

The use of aerial imagery in production agriculture has continued to grow and evolve over the last several years since its debut on the market. With significant changes in how imagery is captured and processed and the quality of images available, there are now many applications for this technology on farms.


Figure 1. On the left is an example of high-resolution imagery from a UAV. From this image it’s possible to detect planter start/stop locations, hybrid differences, and understand the size and location of drowned out areas of the field. The middle image was taken from a manned aircraft. The image on the right is an example of a satellite image with slightly lower resolution than the UAV image. Satellite imagery is a valuable option for evaluating macro level fields trends like drainage issues, but image resolution will be much lower than other sources that capture imagery closer to the ground.

With many choices available for capturing aerial imagery, it’s important to understand the differences and applications to help you make the best decisions for your operation.

The three main options commonly used for aerial imagery in the ag industry are UAVs (unmanned aerial vehicles, or drones), manned aircraft (typically small planes) and satellite-delivered imagery. Drones typically deliver the best image resolution, as they are equipped with high quality cameras and can fly at lower altitudes than manned aircraft. As you can see in Figure 1, imagery taken with a UAV can provide the ability to observe individual rows and plants, as well as clearly identifying planter skips and other areas of lower yield.

To use drones in the agriculture industry, even on your own farm, it’s important to be aware of the legal requirements for owning and operating a UAV. Refer to this previous article for some insight and guidelines.

Drones also offer the best flexibility for timing the capture of images, ensuring that weather and lighting are good for collecting imagery. While battery life for drones has made substantial improvements in recent years, this is still an important limiting factor to consider.

Manned aircraft can also provide high-quality, valuable imagery without the time commitment or overhead costs of using a UAV. Targeting specific weather or times of day is not as easy with manned aircraft because of the preparation required. However, many companies now offer packages that include multiple flights and field maps throughout the growing season for a fixed price. Examples of this type of service Taranis and AirScout. This can be valuable for those interested in aerial imagery without the time commitment and costs of owning a UAV.


Figure 2. A quadcopter-style drone is shown here on the left and a fixed wing drone on the right. These two UAVs operate differently and can each provide unique benefits when utilizing them for agriculture. Typically, fixed wing UAVs will cost significantly more than quadcopter-style UAVs. Image credit: Lynn Betts, Farm Progress

Satellite imagery has been around for decades but continues to make improvements to the quality and timing of imagery available. Many services offer image resolution as high as one meter per pixel, but satellite imagery is often hindered by weather and cloud cover. Several days of overcast could result in missing a desirable image of your crop at a specific growth stage. An advantage of satellite imagery is its archived enabling you to purchase images from last week or even from years ago. Some examples of commonly used ag satellite imagery providers are Planet and Satshot.

UAVs continue to be a popular option for sourcing aerial imagery. Fixed wing drones are more expensive and more difficult to operate, which quickly resulted in the development of app-based software to use quadcopter drones for collecting georeferenced images of fields and stitching them together. Commonly used apps include DroneDeploy, Pix4D and Sentera. While fixed wing drones still have some advantages when mapping larger field areas, the quad copter type still tends to be most common in the ag sector due to their price point, ease of operation, and ability to integrate with third party apps.

This change allowed easier access to high quality field maps, and since then imagery has become widely adopted in the ag industry by everyone from seed companies and ag retailers to farmers using drones to scout their fields.

 


Figure 3. Shown here is an example of a high-level field view obtained while scouting with a quadcopter-style UAV. From this photo we can identify some yellow striping and other areas of reduced crop vigor. The striping in this example was caused by poor-quality dry fertilizer application.

While many product types and services focus on providing orthomoasic images (georeferenced field maps from many images being stitched together), quadcopter-style UAVs also provide other unique and valuable information. The ability to receive a live video feed from the UAV and gain a high level view of the field to evaluate crop vigor, damage, equipment job quality, etc. allows you to evaluate your field in real time. This can often provide instantaneous knowledge about your field and allow for quickly made management decisions to avoid or correct issues identified.

With many options available for imagery sources at multiple price points and quality levels, it’s important to understand each one before making a decision for your operation. Consider your crop scouting needs and the information you would like to gather before choosing an imagery source.

 

 

 

 

Table 1. This is an overview of some common advantages and disadvantages of the types of aerial imagery sources discussed in this article.

 

Quadcopter UAV

Fixed Wing UAV

Manned Aircraft

Satellite

Pros

  • Simple to use
  • Instantaneous feedback for scouting
  • Can provide high resolution maps

 

  • Automated flights
  • Can cover more acres/hour when mapping compared to a quadcopter
  • Lower overhead cost than owning a UAV
  • Typically provides multiple stitched images (NIR, RGB, NDVI, etc.)

 

  • Low cost
  • Archived historical data
  • Smaller, more manageable file sizes

 

Cons

  • Often only able to capture a single image type (RGB, NIR, thermal) during flight
  • Productivity often limited by battery life
  • Field maps can be large and difficult to manage
  • High cost to purchase– typically over $10,000
  • More complex to operate
  • Field maps can be large and difficult to manage

 

  • Longer wait time between ordering and receiving images/maps
  • Less flexibility with flight altitude (i.e. image resolution) and sensor packages
  • Lowest resolution of all options
  • Images often may be impacted by cloud cover

Cost

$500 - $10,000

$10,000+

$1-$5/acre

$0.20/acre

Authors: 

Ryan Bergman Program Coordinator in Ag Technology

Ryan Bergman is a Program Coordinator in Ag Technology at Iowa State University where he is part of a 20+ person research team focusing on precision agriculture, big data, telematics, data analytics, aerial imagery, and ag machinery automation. Ryan has received both his bachelor’s and mas...