Chapter 3: Landsat Images
Landsat is a public domain, meaning: under an “open skies” policy, images are acquired of the
entire earth without obtaining permission from any government; and users anywhere in the world
may purchase all images at uniform prices and priorities.
Landsat 1, 2, & 3: altitude 918km, 18 day repeat cycle, on-board data storage
Landsat 4 & 5: altitude 705km, 16 day repeat cycle
MSS: 4 bands (0.5 – 1.10 microns), terrain 185 by 185 km, ground cell 79 by 70 m
TM: 7 bands (0.45 – 2.35 microns, 10.5 – 12.5 microns), terrain 185 by 170 km, ground cell 30
by 30 m (VIZ and NIR) and 120 by 120 m (TIR)
TM imaging system records data on the east-&westbound sweeps with a slower scan rate, longer
dwell time, and higher signal-to-noise ratio than MSS.
TM colour combinations:
Display Advantages Disadvantages
1-2-3 Normal colour image. Optimum for Lower spatial res due to band 1. Limited
mapping shallow bathymetric features. spectral diversity b/c no RIR bands used.
2-3-4 IR colour image. Moderate spatial res. Limited spectral diversity.
4-5-7 Optimum for humid regions. Max Limited spectral diversity b/c no viz bands
spatial res. used.
2-4-7 Optimum for temperate to arid Unfamiliar colour display, but interpreters
regions. Max spectral diversity. quickly adapt.
Both generations of Landsat are placed in sun-synchronous orbits, where the southbound swath
covers daylight and the northbound swath covers the dark hemisphere. Polar latitudes greater
than 81 are not covered. Rotation of the Earth shifts the image swaths westwards every 24
hours. This orbit pattern causes the corresponding orbits in each repeat cycle to occur at the same
time. Advantages are: areas with persistent clouds may be imaged on rare cloud-free days;
images may be acquired at the optimum season for interpretation; and repeated images record
changes since 1972.
All Landsat images are referenced to path-and-row index maps where the path is the southbound
segment of the orbit path.
First, define and map the lithology. Next, map the geologic structures: attitude of beds
(highlights and shadows), folds and faults (offsets). Prepare a cross section and check the
interpretation in the field.
Advantages of wet-season image: windblown dust causes atmospheric haze which is mostly
removed by rainfall, also washing away surface dust from outcrops; greater soil moisture
enhances tonal and colour differences between rock types; and vegetation grows preferentially
on belts of soil with higher moisture and help delineate geology trends. Chapter 5: Thermal IR Images
Thermal IR is in the range of 3 – 15 microns, but because of atmospheric absorption by the
ozone layer, satellite images for TIR are taken at 10.5 – 12.5 microns, while aircraft can take the
Kinetic heat is the E of particles of matter in a random motion that is converted to radiant energy.
A calorie is the amount of heat required to raise the T of 1g of water 1 C. Temperature is a
measure of the concentration of heat, T kin(kinetic T) is a measure of the conc’n of kinetic heat.
Radiant flux (F) is the em E radiated from a source and T radis the measure of conc’n of F.
Heat transfer occurs by one of three methods: conduction (contact), convection (physical
movement), and radiation (em waves).
Reflected IR region: 0.7 to 3 microns (inc