Coastal Services Center

Summary

Airborne thermal infrared radiometers (TIR) are used to map and measure thermal characteristics of landscapes and seascapes. These instruments are often components of complex remote sensing systems that incorporate visible sensors, airborne inertial measurement units (IMU), differential global positioning units (DGPS), data storage devices, and specialized software for georeferencing. Thermal imagery can be collected at customer specified ground-resolutions and temperature ranges.

Thermal infrared radiometers used in mapping applications are calibrated to maintain consistency among images collected during a mission. Midwave and longwave radiant energy (3 to 5 and 8 to 14 micrometers) emitted from the ground, water, and other objects is captured by airborne sensors on linear arrays or focal plane arrays and stored as digital numbers. Post-processing of the raw data produces temperature data that are applicable to a wide variety of mapping needs.

TIR Data Product

Point to the names below to view a thermal infrared image and a true color image of the same area. The thermal image was collected to support temperature total maximum daily loads (TMDL's) on the Molalla and Pudding Rivers in Northern Oregon. The objective of the survey was to map longitudinal temperature patterns in the river and to identify and measure source temperatures (i.e. tributaries, surface springs, irrigation returns). The image below shows the confluence of the Pudding River (26.0°C) and the Molalla River (24.1°C). A surface spring (13.8°C) is visible along the left bank just upstream of the confluence. (Flow direction is from the bottom to the top of the image.)

Applied Uses

Examples of how TIR data are being used:

Identifying Nonpoint Sources of Fecal Coliform Fecal coliform bacteria can cause beaches and shellfish beds to close. Coastal managers in South Carolina are testing forward looking infrared (TIR) imagery to see if this technology can help identify leaking septic tanks near the shoreline, a common source of fecal coliform.

Other Potential Uses:

• Stormwater discharge detection
• Stream temperature monitoring
• Marine mammal surveys
• Fire detection and mapping
• Law enforcement
• Search and rescue
• Power line inspection

Specifications

Spatial Resolution

Spatial resolution is dependent on the field of view, array dimensions of the sensor, and the altitude at which the aircraft flies.

Temporal Resolution

Revisit rate is dependent upon flight scheduling.

Data Ordering Details

Data Acquisition	Several private companies collect TIR data from both helicopter and fixed-wing platforms, depending on the project.
Timing	Many time constraints are associated with TIR imagery collection and delivery. Flight schedules can be delayed due to seasonal restrictions, weather, and environmental factors. Project areas may be large enough that multiple flights are needed. Post processing can be time consuming. Producing additional deliverables can delay the delivery schedule.
Cost	Cost can vary depending on size of the project, spatial accuracy, and project location. Cost may also increase based on specific accuracy requirements and the products requested.
Data Formats/Software Needed	There are no standard file formats for TIR imagery. Vendors deliver imagery in BIL or Arc/Info GRIDS, and GeoTiff formats which include actual radiance and/or temperature values and allow for additional processing. Other image formats such as BMP, JPEG, and TIFF provide scaled graphics and do not retain the raw data values.

Frequently Asked Questions

Data Acquisition

Can I download or request TIR imagery on-line?
Several vendors have example imagery available at their Web sites.

Cost

How much does it cost?
Cost can vary depending on size of project, environmental constraints, spatial resolution, and spatial accuracy.

Accessories and Hardware Needed

What types of hardware are required?
Calibrated thermal infrared radiometers provide a means to convert digital numbers to radiance values for storage as in onboard devices. Sophisticated TIR systems also include gyro-stabilization, airborne inertial measurement units (IMUs), and global positioning systems (GPS) to prevent image degradation and permit image geo-location and rectification.

What additional sensors accompany a TIR mission?
Advanced mapping grade TIR systems often include a separate digital video or frame camera that collects visible imagery. This imagery provides context to help interpret the thermal imagery.

Data Formats and Software Needed

What are some of the TIR products available?
Airborne thermal infrared imagery is recorded as scaled radiance data. Additional processing with advanced software packages may correct for atmospheric, background, and target emissivity effects and produce calibrated temperature data.

What types of software are required?
Airborne thermal infrared imagery is commonly formatted as standard image files. Any software capable of processing 8-bit or 12-bit data can view the imagery. Examples include the following:

• Adobe PhotoShop
• Paint Shop Pro

Higher-end image processing and analysis will require specialized software, including the following:

• ESRI products (ArcView, ArcInfo, ArcGIS, etc.)
• ERDAS IMAGINE and OrthoBASE
• ER Mapper
• RSI ENVI

Is freeware available for using these data?
A number of freeware viewers will allow you to view image data and perform simple tasks. It is recommended that you contact the software companies for more details. The following are some examples of freeware viewers:

For more Information