Landsat 8 Photoshop Tutorial

Introduction

This tutorial, aimed at mapmakers and illustrators, discusses where to get and how to make Landsat 8 scenes in Adobe Photoshop. The focus is on creating natural-color images that look similar to what an astronaut looking down at Earth would see. Creating 3D oblique views is another use for Landsat 8 images (Figure 1).

Although Landsat 8 is a scientific product intended for use with specialized remote sensing software, Photoshop's graphical tools work very well with it. Intermediate Photoshop skills are required for most of the procedures discussed in this tutorial. Some of the more advanced procedures require Geographic Imager, a GIS plug-in for Photoshop.

Figure 1. Flying into Los Angeles. A Landsat 8 image draped on a 30-meter DEM.

Landsat 8 at a glance

• The Landsat 8 program, jointly managed by NASA and the USGS, provides satellite data that is in the public domain and free.

• Landsat 8 became fully operational on April 11, 2013.

• The satellite orbits Earth every 99 minutes at an altitude of 705 kilometers (438 miles) in a polar orbit. The satellite records the daylight side of Earth on the soutbound leg of its orbit.

• Landsat 8 collects about 400 new scenes comprising 400 GB of data every day. Processed data becomes available to the public within 24 hours of collection.

• Despite voluminous data collection, it will take several years before cloud-free scenes are available for most areas. Obtaining cloud-free images of some very wet tropical areas may never happen.

• Regular coverage includes the area between 82° 40' north and south latitude. Off-nadir (sideways looking) scenes extend coverage to slightly higher latitudes, but not as far as the poles.

• The satellite returns to the same place on Earth occur every 16 days and at the same time of day. It records new scenes depending on the weather below and other collection requirements.

• The mid morning hours are when the satellite records scenes everywhere on Earth. It crosses the equator at around 10:00 AM.

• Scenes are north-oriented. However, because Earth rotates east as the southbound satellite flies over it, the area covered in scenes follows the northeast to southwest trending flight paths.

• Along flight path axes, Landsat 8 scenes measure 185 kilometers wide by 170 kilometers tall (115 x 105 miles).

• Landsat 8 does not take photographs. Rather the satellite's two sensors collect data from discrete portions of the electromagnetic spectrum known as bands and determined by their wavelength. There are 11 bands. Some of the bands represent portions of the electromagnetic spectrum invisible to the human eye (Figure 2).

• Landsat 8 scenes are georeferenced and orthorectified to elevation data. They are in the UTM/WGS 84 coordinate system.

• Downloaded Landsat 8 bands come as 16-bit grayscale geotifs, which are ordinary .tif images, but with extra georeferencing information. Note that the satellite sensors collect raw data at the 12-bit depth. Interpolation accounts for the greater bit-depth of the released data.

• The ground resolution (how much distance each pixel represents on Earth) of the bands is generally 30 meters. Band 8 containing panchromatic data at 15-meter resolution is an important exception. Bands 10 and 11 are upsampled to 30-meter resolution from data collected at 100-meter resolution.

Figure 2. Landsat 8 bands

Next: Getting the data