Thermal Infrared Radiometer
Summary | TIR Data Product | Applied Uses | Specifications | Data Ordering Details | Frequently Asked Questions | For More Information
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.)
Images provided courtesy of
Oregon Dept. of Environmental Quality (2004)
and Watershed Sciences, Inc., Corvallis, OR
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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
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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.
Company and Sensor |
Spectral Range |
Array (pixels) |
Sensitivity |
Field(s) of View |
Instantaneous Field of View |
FLIR Systems Thermovision 1000 |
8 – 12 µm |
800 x 400 |
0.15° at 30° C |
20° x 13°
5° x 3° |
0.6 mRad
0.15 mRad |
FLIR Systems ThermaCAM SC3000 |
8 – 9 µm |
320 x 240 |
0.02° at 30° C |
10° x 7.5°
20° x 13° |
0.55 mRad |
Space Instruments FireMapper |
8 – 12.5 µm
8.8 – 9.1 µm
11.3 – 12.4 µm |
320 crosstrack (pushbroom) |
0.1° C |
63.3° crosstrack |
3.85 mRad high
resolution is available |
ITRES
TABI–320 |
8 – 12 µm |
320 x 240 |
0.1°C at 0 – 50° C |
48° crosstrack |
2.8 mRad |
ITRES
TASI–600 |
8 – 11.5 µm |
600 x 240 |
0.11° C at 100° C |
40° crosstrack |
1.25 mRad |
Temporal Resolution
Revisit rate is dependent upon flight scheduling.
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Data Ordering Details
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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:
General Questions
Can TIR sensors detect subsurface water inflows?
TIR imagery collected over water represents the radiance or temperature at the surface of
the water. This is because water is generally opaque to thermal wavelengths. Therefore,
detection of subsurface water inflows is dependent on the magnitude of vertical mixing
within the water body and the thermal contrast between waters of different origin.
How important is mission planning?
Mission planning is very important. Depending on the goals of the data acquisition effort,
flights may occur at specific times during the day and year. Successful mission planning
maximizes the thermal contrast detected by the TIR sensor allowing the data analyst to
discern target features more easily. Ground truthing is also an important aspect that
must be considered and conducted if accurate temperatures (e.g. < 1.0° C) are important
to the mission.
What level of technical expertise is needed to use imagery?
A general understanding of the software is needed to view the imagery. Image processing
and analyses of TIR data may require a trained technical person.
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For more Information
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