This page will house the deliverable (an implementation guideline) for AgGateway's PICS project.

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1. Overview

This document contains guidelines for establishing a common approach to sharing image data used in agriculture. By creating these guidelines, AgGateway seeks to optimize the quality of information obtained from those images. Such an approach would alleviate several issues that obstruct image usability, by providing:

• Transfer of complete, intact image information
• Image clarity
• Descriptive textual detail to further explicate each image
• Time and date stamping of images for accurate reference

1.1 AgGateway

AgGateway is a non-profit consortium of businesses serving the agriculture industry. Together, its members focus on promoting, enabling, and expanding eBusiness in agriculture. As a long-term vision, AgGateway endeavors to establish itself as a trusted source for enabling eAgriculture. To do this, its member businesses aim to succeed, collectively by:

• Improving business processes
• Helping to deliver excellent customer service
• Streamlining the supply chain
• Supporting greater productivity and sustainable agricultural practices.

Through this collaboration, AgGateway not only designs effective industry-wide solutions, but implements those solutions in the field, ensuring that eConnectivity becomes a working reality.

1.2 PICS

AgGateway designed the Post Image Collection Specification (PICS) to support agricultural remote sensing. To do this, the PICS process uses the GeoTIFF graphics format with defined metadata tags that specify what an image means. Use of PICS requires access to this free PICS Implementation Guideline.

2. Problem Definition

The complex, multispectral nature of today’s electronic images complicates their usability and scalability. While that nature allows for capture of much information, the ability to share the range of that information has not kept pace. For example, a grower’s FMIS can’t automatically recognize and “comprehend” the details of a particular image. This results in the need for users to manually extrapolate the information, making use of imaging slow and frustrating rather than useful.

3. Solution Approach

The PICS strategy, developed by AgGateway’s Precision Ag Council, addresses the image sharing problem through the following plan:

3.1 Identify Gaps

To start, the team noted the gaps that currently exist in remote sensing image data. Those gaps were identified as the specific pain points that render images useless in terms of interoperability. For the initial solution, these gaps included:

• Where an image was taken
• When an image was taken
• What bands are included in the image
• The order of the bands in the image
• Whether the writing software is PICS-aware

Later refinements of this solution may include:

• Creating a registry of derivative products, such as NDVI
• Expressing mathematical conversions for characteristics such as digital values, reflectance, or irradiance

3.2 Apply Standards

Next, the team agreed on the steps to take to resolve each of those pain points, in a way that incorporated as many existing standards as possible.

3.3 Refine Focus

From here, the team narrowed the scope of their plan, focusing on a single, popular image format to simplify the solution.

3.4 Document Guidelines

Finally, the team established implementation guidelines that would enable users to easily apply the PICS strategy. This document serves as that guide, resulting in the main deliverable for the PICS project.

4. Solution Description

4.1 Why GeoTIFF

GeoTIFF, a popular, royalty-free format, provides sophisticated tagging that simplifies communication of image data. As depicted in the following illustration, GeoTIFF stores the band data from an image in a digital file. From this band data, GeoTIFF defines tags, creating metadata.

4.2 Tags

The tags created by GeoTIFF, when implemented according to this guide, ensure that tagging is consistent, and that it conveys the information needed by FMIS software. That information includes band order, geometry, and acquisition time.

5. Implementing PICS

Publishing PICS compliant imagery requires specific information to properly tag an image. It also requires the ability to write those tags to the receiving image products.

5.1 Publishing Data

5.1.1 Requirements

For proper tagging, data must be captured in GeoTIFF format version 1.0 or newer. Regarding band values, black is represented by a zero.

Successful tagging of an image requires collection of the following critical pieces of information:Central wavelength of each band

• Order of the bands (if multiple layers)
• General name of the band
• Start and end times that express when an image was acquired

All tags have specific formats and locations within the GeoTiff. PICS uses GeoTIFF, XMP and EXIF tags to ensure full expression of an image.

5.1.2 Limitations

Some limitations affect image tagging. Among these: Use of GeoTIFF imposes a limitation of 4GB for image transfer. This constraint can be remedied, however, by use of either BigTIFF or tiles.

Tiling an image segments it into a number of smaller rectangular areas called tiles. If you use a JPEG2000 image, the tile size defined in the image, ca be used to create an IDLgrImage object. Another method – creating an image pyramid – does not have an inherent tile size defined, allowing for the default tile size of the IDLgrImage object (1024 by 1024 pixels).

The size of the drawing area, the tile size, and the image level all play a part in the display of a tiled image. With a large, full-resolution image, only a portion of it appears in the view, so only a subset of the image tiles are displayed. In the following figure, the full-resolution, level 0 image is shown on the left. Only two of the 1024 by 1024 tiles are loaded to support what appears in the 800 by 800 pixel drawing area, indicated by the dotted box in the following illustration.

If you zoom out to a zoom level of 50% or less, IDL can show the level 1 image (which is half the resolution of the level 0 image). Only a single tile is required to fill the drawing area. If you reduce the zoom level by another 50%, the level 2 image can be displayed, and the entire image is visible in the drawing area.

5.2 Consuming Data

Consuming imagery that is PICS v1.0 compliant requires knowledge of its tags and the ability to read them. Again, image size can affect and limit this process.

Tiling, such as that supported by an IDLgrImage object, allows display of images that are too large to be read entirely into memory. For example, satellite images can exceed a gigabyte of data, making it impossible to display as a single unit on a typical business computer. Such an image can be displayed by segmenting it into smaller images, or tiles.

Tiling enables rendering of an image without any data. That is, the image pixels load only when the tile section comes into view during panning. Image pyramids can also be used to support level of detail (LOD) rendering for large images. This changes the resolution of an image when zooming in or out within an image display. As you zoom out, successively smaller, less detailed images can be displayed. This allows for a full view of the larger image with selection of areas of interest for zoom-in. During that zoom-in, progressively detailed image layers can be loaded. The IDLgrImage object is aware of the LOD required and will communicate that to the application when the application requests the tile visibility information. 

6. Conclusion

TBD

PICS Story Book

The following examples present simulated instances that describe how users can apply the PICS strategy for addressing their needs in publishing and consuming image data.

Insurance Story

An insurance company is interested in some topographical scenes a satellite company has archived, and wants to combine that with manned aircraft imagery after large scale hail events to compare damages rapidly and aid the adjustment effort. The insurance company purchases the required imagery from the satellite provider and quickly does analysis on the data gathered from the manned aircraft. They provide this to field agents to aid their adjustment efforts more quickly and precisely.

Analytical Story

A farmer wants to do some specific analysis on his farm using data he has gathered from his UAV; however, the farmer does not know when to fly or how to do the analysis. The analytical company uses weather, planting, soil fertility, and historical and current satellite data to alert him when he should fly. Once deployed, the UAV gathers specific bands of information at the proper time, which is processed and used in the specific analysis. The analytical company checks the data for compliance and produces advice for the farmer. This is then used to help the farmer make key decisions that help improve their yield and operation.

Cooperative Story

A cooperative provides a service to its members that monitors, scouts, and alerts them to issues. In the spring the Co-op contracts a manned aircraft to fly all the group of fields nearest to them, but a few fields are further out and require UAVs to capture data. The data is then used to determine scouting locations well as do stand assessment in early spring. Both the manned aircraft and UAV data is RGB and needs to be brought into the same portal. Later in the year the first manned aircraft provider is not available but data needs to be gathered, so another provider is contracted and UAVs are used to fill in the blanks. Some fields later require different types of data for specific analysis before putting on fertilizer and the UAV is used with a multispectral sensor to capture the proper data. Regardless of the system used the data can be imported, used, and displayed to each member of the cooperative.

Preferred Image Format:

Why GeoTIFF?

• GeoTIFF meets the projection requirements

  Other Benefits:

  • Compression
  • Radiometry
  • Transformation
  • Public domain metadata standard (for encoding/decoding)
  • Open Source component GDAL plugin (MIT license)
  • Possible to include aux/sidecar files

GeoTIFF Specifications

• GeoTIFF v 1.0 - http://web.archive.org/web/20160403164508/http://www.remotesensing.org/geotiff/spec/geotiffhome.html
• TIFF 6.0 specifications - http://partners.adobe.com/public/developer/en/tiff/TIFF6.pdf

Known Limitations:

• 4GB limit, to be remedied by using the proposed BigTIFF format - http://bigtiff.org/
  
  • Anything larger than 4GB needs to utilize BigTIFF specifications
  • Can also be solved by breaking large tiff files into 4GB tiles and using virtual layers

Additional Tags Required:

GeoTIFF does not supply all the tags necessary to define information such as spectral band width, band center wavelength, name or acquisition time or duration.  Using both the EXIF and XMP tags shown below the PICS requirements can be satisfied.

Other Image Formats:

GeoTIFF was selected as a preferred format for many reasons, but primarily because it is adaptable to so many projections and flexibly for re-projection makes it desirable.  It is not recommended but the EXIF and XMP tags outlined can also be used with other image formats such as ".jpg" or "png" but these other formats may lack projection unless a sidecar/auxiliary file is used.