Raw Data

Objectives

Introduction

The ETM+ sensor on Landsat 7 scans a scene and sends data from its 7 bands and the panchromatic sensor to a ground station. The data for a single scene taken by the Landsat 7 ETM+ includes image data for each of the bands and for the panchromatic sensor and is stored as image data. The images are usually corrected for radiometric and geometric distortions and are then made available as a complete set of raw data.

Band	Spectral Range (microns)	Electromagnetic Spectrum	Ground Resolution (m)
1	.45 to .515	Visible blue-green (reflected)	30
2	.525 to .605	Visible green (reflected)	30
3	.63 to .690	Visible red (reflected)	30
4	.75 to .90	Near Infrared (reflected)	30
5	1.55 to 1.75	Mid-Infrared (reflected)	60
6	10.40 to 12.5	Thermal Infrared (emitted)	30
7	2.09 to 2.35	Mid-Infrared (reflected)	30
Pan	.52 to .90	Visible light (reflected)	15

Band 1

[BAND 1 IMAGE OF SCENE]

The spectral response of Band 1 is in the Visible portion of the electromagnetic spectrum that corresponds with blue-green light. Energy at this portion of the electromagnetic spectrum is easily scattered by particles in the atmosphere, often giving images in this band a hazy appearance. This band is capable of being transmitted through water and is especially sensitive to particles suspended in water (such as sediments and algae). Data from this band can be used with bands 2 and 3 to create "true" color composite images, which most closely approximate how the scene would appear to the human eye.

Band 2

[BAND 2 IMAGE OF SCENE]

The spectral response of Band 2 is in the Visible portion of the electromagnetic spectrum that corresponds with green light. It can be used with bands 1 and 3 to create "true" color composite images.

Band 3

[BAND 3 IMAGE OF SCENE]

The spectral response of Band 3 is in the Visible portion of the electromagnetic spectrum that corresponds with red light. It is also one of the three component bands used to create "true" color composite images.

Band 4

[BAND 4 IMAGE OF SCENE]

The spectral response of Band 4 is in the Near Infrared (NIR) portion of the electromagnetic spectrum. This form of infrared sits just outside the visible red light portion of the electromagnetic spectrum. This form of radiation is reflected to a high degree off leafy vegetation since chlorophyll (the green pigment in green vegetation) reflects much of the NIR that reaches it (it has a high albedo in this band).

Band 5

[BAND 5 IMAGE OF SCENE]

The spectral response of Band 5 is in the Middle Infrared (Mid-IR) portion of the electromagnetic spectrum. This portion of the spectrum is sensitive to variations in water content in both leafy vegetation and soil moisture. This band allows an observer to distinguishes between clouds (which appear dark) and bright snow cover (which appear light). Sensors in this band also respond to variations in ferric iron (Fe2O3) in rocks and soils, showing higher reflectance as iron content increases. This allows one to use these data to determine mineral content and soil types from space.

Band 6

[BAND 6 IMAGE OF SCENE]

The spectral response of Band 6 is in the Thermal Infrared portion of the electromagnetic spectrum. Thermal infrared is radiation that is detected as heat energy, therefore the thermal IR band effectively measures the temperature of the surfaces it scans. Band 6 on the ETM+ sensor can distinguish temperature difference of about 0.6 Celsius, which allows it to detect relatively small differences in land and water surface temperatures. This makes the thermal IR band useful for a variety of purposes. For example, using band 6 data, researchers can discriminate among rock types whose thermal properties show differences in temperature near the surface. This assists researchers in creating geologic mapping of land surfaces from space. This data supports agricultural and mineral exploration efforts. ETM Band 6 data can detect changes in ground temperature due to moisture variations, assisting in drought planning, flood forecasting, and agricultural assessment. The cooling effect of water evaporating from vegetation can be detected, assisting in efforts to map land use characteristics of a region.

Band 7

[BAND 7 IMAGE OF SCENE]

Spectral response of Band 7 is in the Middle Infrared (Mid-IR) portion of the electromagnetic spectrum. This portion of the electromagnetic spectrum is sensitive to moisture and thus responds to the moisture contents in soils and vegetation. The sensitivity to moisture contents is suited to detecting certain water-loving minerals, such as clays, in geologic settings. This band is also useful in detecting moisture levels in leafy vegetation, which can change under certain environmental conditions (e.g. drought, pollution, insect infestation) and thus provides a means to monitor productivity and identify agricultural areas that are under stress.

Panchromatic

0.52 to 0.90 picometers black and white sensor with a 15 m spatial resolution. The higher resolution of this data assists land-use researchers by making identification of smaller objects easier. Items smaller then 30 m will appear fuzzy or ill defined in the 30 m bands of the ETM+. The 15m resolution of the panchromatic band will allow researchers to make better determinations of land use and will assist in producing accurate land use maps of a region.