This page will house houses the deliverable (an implementation guideline) for AgGateway's PICS project.
November 21 update: The PICS team is actively working on the text of the implementation guideline. Please check back soon, but meanwhile, please take a look at the informative This guideline follows the introduction made in the flyer:
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Table 1: Tags used by PICS, and the pain points they target.
Pain point | Why it hurts | The PICS solution |
Band order | Identifying individual bands in multi-channel images often requires a sidecar file or arbitrary naming conventions. This can lead to confusion, especially if the sidecar file is lost. | Implement the standard tag Xmp.Camera.BandName |
Band Definition | An accurate description of a band’s width and central wavelength enables knowing if it can be used to make specific indexes and other products. | Implement two standard tags: Xmp.Camera.CentralWavelength Xmp.Camera.WavelengthFWHM |
Acquisition Time & Duration | Knowing when an image was captured helps sort files for proper analysis, and flag / filter unwanted data. This is important with long UAV acquisition times. | Implement three standard tags: Exif.GPSInfo.GPSDateStamp Exif.GPSInfo.GPSTimeStamp Xmp.Camera.AcquisitionDuration |
Projection Information (Geolocation) | It’s critical to locate individual image pixels and support multiple coordinate systems and projections. | PICS chose the GeoTIFF image format because it natively enables the needed functionality. |
PICS compliance & version | Can the FMIS trust that the tags are used in a PICS-compliant way? | A private AgGateway tag (with tag number 65265) is added to the image, formatted as a PAIL Observations document with a ContextItem. |
5. Implementing PICS
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Table 2: Specifics about PICS tag definitions
Item | Tag Type | Key | Type | Notes |
Band Name | XMP | Xmp.Camera.BandName | XmpSeq | Name of each band (sequence). Single page image: one name for each band of the image. Multipage image: one band name per image page; each page should have only one band. |
Band Center Wavelength | XMP | Xmp.Camera.CentralWavelength | XmpSeq | Central wavelength of each band in nanometers (nm). |
Band Width | XMP | Xmp.Camera.WavelengthFWHM | XmpSeq | Full width half maximum of the wavelength distribution in nanometers (nm). |
Acquisition Date | EXIF | Exif.GPSInfo.GPSDateStamp | ASCII | Mean GPS date as year, month, day (UTC) in the format “YYYY:MM:DD" |
Acquisition Time | EXIF | Exif.GPSInfo.GPSTimeStamp | List of Rational | Mean time of capture - GPS time as hour, minute, second (UTC), with sub-second accuracy |
Acquisition Duration | XMP | Xmp.Camera.AcquisitionDuration | XmpText | Time duration taken to acquire all images in dataset, measured in seconds |
Versioning | GeoTIFF | 65265 | ASCII | This is using the PAIL schema to accomplish recording a version. |
5.1.3 Date & Time
When tagging imagery for date and time it is critical to agree on a standard time reference. In the PICS case it was decided to use the GPSDateStamp and GPSTimeStamp which are in based in Coordinated Universal Time (UTC) with an offset of +0000, by using GPSDate/TimeStamp it eliminated the confusion of a more ambiguous tag called DateTimeStamp that has no time zone reference. The GPS time stamp provides clarity because it is always displayed in UTC. One example might be a satellite image which is not using official GPS time, but it’s internal clock (likely in UTC) could be used for this tag.
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Table 3 - Canon S110 - Modified NIR Data
Band names: | Red, Green, NIR |
Band width (nm): | 90, 70, 100 |
Band center wavelength (nm): | 625, 560, 850 |
Acquisition Date (UTC): | 2015:06:26 |
Acquisition Time (UTC): | 18:38:52 |
Acquisition Duration (s): | 1540 |
Table 4 - senseFly ThermoMAP - Thermal Data
Band names: | Thermal IR |
Band width (nm): | 3000 |
Band center wavelength (nm): | 10000.5 |
Acquisition Date (UTC): | 2015:06:23 |
Acquisition Time (UTC): | 20:31:19 |
Acquisition Duration (s): | 1328 |
Table 5 - SenseFly S.O.D.A. - RGB Data
Band names: | Red, Green, Blue |
Band center wavelength (nm): | 660, 550, 470 |
Acquisition Date (UTC): | 2017:06:05 |
Acquisition Time (UTC): | 18:55:34 |
Acquisition Duration (s): | 3426 |
* Note there are no band widths defined
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Table 6 - Parrot Sequoia - Multispectral Data
Band names: | Green, Red, Red Edge, NIR |
Band width (nm): | 40, 40, 10, 40 |
Band center wavelength (nm): | 550, 660, 735, 790 |
Acquisition Date (UTC): | 2017:07:07 |
Acquisition Time (UTC): | 20:56:54 |
Acquisition Duration (s): | 2049 |
* each individual image is tagged separately with name, band width, center wavelength
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