Lab 08 - Map making

The purpose of Lab06 is to familiarize you with interpreting Landsat Thematic Mapper and SPOT imagery. Upon completion of this lab you should be aware of the usefulness of each TM band, and the similarities and differences between TM and SPOT data.

Outline:

Materials (click to download)

Terminology electromagnetic energy – energy rays that are either reflected or emitted as radiation by objects. X-rays, ultraviolet light, visible light, near-infrared light, and heat (thermal) radiation are different wavelengths of electromagnetic energy electromagnetic spectrum – continuum of electromagnetic energy from long wavelengths such as radio or radar, to medium wavelengths like visible light, to short wavelengths like X-rays panchromatic – sensitive to all or most of the visible electromagnetic spectrum color composite – putting 2 or 3 MSS bands together in a color image LANDSAT – series of satellites managed as part of NASA’s Earth Observing System that acquire imagery of the Earth from space. The images are used in the areas of global change, agriculture, geology, forestry, regional planning, education, and national security

Electromagnetic Spectrum The electromagnetic spectrum includes visible light, radio waves, heat, X-rays and other forms of electromagnetic energy (EMR). A multispectral sensor samples EMR in various discrete wavelength ranges. A panchromatic sensor samples EMR over a single broad range of wavelengths. Multispectral imagery is useful for analyzing spectral signatures (patterns of reflectance in various wavelengths) of Earth features.

EM_Spectrum_Properties_edit.png Types of Resolution Spatial Resolution • Size of pixel; the smallest digital element that is displayed, pixel stands for “picture element”. • The smaller the area that the pixel can detect , the higher the spatial resolution • Higher spatial resolution means more detail is captured and displayed. Spectral Resolution • how narrow a wavelength the sensor is sensitive to • more bands covering a the same portion of the spectrum has a higher spectral resolution (e.g. 5 bands covering 0.3-0.7µm has a higher spectral resolution than another dataset with 3 bands covering the same 0.3-0. • 7µm) Temporal Resolution • how often the satellite goes over the same place on earth, often called the revisit period. However some sensors have off nadir data acquisition, the revisit period may not equate to a complete orbit cycle • increased frequency = high temporal resolution Radiometric Resolution • range of digital number values (don’t worry about this now)

Pixels and Digital Numbers • reflected light energy is converted into a digital number (DN) and stored in pixel format • digital number = positive integer value proportional to reflectance • DNs are in a column by row format DNRep.png • each is a pixel & has a DN • different satellites have different pixel sizes MSS 79m by 56m TM 30m by 30m (visible, near-infrared and middle infrared) SPOT 5 10m by 10m • SPOT has the highest spatial resolution

Landsat Thematic Mapper (TM) • High spatial resolution; improved geometric accuracy; greater radiometric detail; more precise spectral resolution Band Spectral Definition Spatial Resolution 1 Blue/Green 30m x 30m 2 Green 30m x 30m 3 Red 30m x 30m 4 NearIR 30m x 30m 5 MidIR 30m x 30m 6 FarIR (Thermal) 120m x 120m 7 MidIR 30m x 30m

• Bands 1-5, 7  detect reflected energy • Band 6  detects emitted radiation • Landsat passes over US in the morning, keep in mind where the sun is at that time

TM Data Characteristics • Characteristics of bands selected to maximize detecting & monitoring of different types of resources • TM band1 – penetrates water; useful for coastal studies, soil-vegetation differentiation, forest type distinction • TM band 4 – detects nearer reflectance peaks in healthy vegetation; useful for water/land interfaces • TM band 6 – used for thermal mapping

TM False Color Composite • Combination of TM2, TM3, & TM4 assigned to B,G, and R color guns, respectively • So that: o Vegetation appears as shades of red (the brighter, the healthier) o Soils/sparse vegetation range from white (sands) to greens/browns depending on moisture or organic matter o Water bodies appear blue; deep clear H20 dark blue to black; sediment laden H20 lighter o Urban areas appear blue/gray o Clouds/Snow appear bright white

SPOT (Le Systeme Pour l’ Observation de la Terre) • “Earth Observation System”; French system • Operates in 2 modes: panchromatic & multispectral • SPOT 4-5 Multispectral Mode Band 1  Green Band 2  Red Band 3  NearIR Band 4  SWIR(short-wave infrared) Spatial Resolution:10m~ 20m • Panchromatic Mode Sensitive across broad spectrum (.51 - .73 μm) Spatial Resolution =2.5 m~5m

Quick Reference Comparison Chart MSS TM SPOT 5 Spatial Resolution 79 x 56 30 x 30; 120 x 120 (TM6) 10 x 10; 20 x 20 #bands 4 7 4+ pan. Temporal Res. 18/16 16 26 Cost Free Free Varies: 10m full scene ~$4,500 Start date 1972 1982 2002 (SPOT1 from 1986) Radiometric 0 – 127 0 – 255 0 – 255 ** Radiometric Resolution – range of values that DN can be assigned

SPOT recently launched SPOT 6 on September 9, 2012. You may find the details in http://www2.astrium-geo.com/files/pmedia/public/r12317_9_spot6-7_technical_sheet.pdf

Beside MSS (Landsat 1-4) and TM (Landsat 5), the Landsat program has ETM+ (Landsat 7), and recently launched, Landsat 8 (launched February 11, 2013). WRS: Landsat imagery uses the World Reference System (WRS) to spatially index images. WRS-2 is a grid index of scenes acquired for Landsat 4, 5, & 7. The index is comprised of 233 paths and 248 rows. An individual scene location can be determined using the combination of path and row (path/row).

Part 1: Landsat TM

1. Fill in the table below (use the tables in your textbook): (7 points)

            TM Bands	                				 
   

   Band Wave Length Pixel Size/Resolution

   1 ______________ _______________

   2 ______________ _______________

   3 ______________ _______________

   4 ______________ _______________

   5 ______________ _______________

   6 ______________ _______________

   7 ______________ _______________ Copy the TM scene (.img and .rrd file) from G:/ Fall-2015/G526/Lab06/. The image is called I5016037_03720050727.img & be sure to copy I5016037_03720050727.rrd as well. Note that this image has been processed at a Level 1T. See this link for a description of the processing. http://landsathandbook.gsfc.nasa.gov/data_prod/prog_sect11_3.html

Open ERDAS Imagine 2014, and open the TM image listed above in a 2D Viewer.

2. A) According to the website above, what projection should the data be in? _______________________ (1 point)

B) Verify the projection by opening the metadata for the image in ERDAS (right click on the image name  Metadataclick Projection tab). Is the image in the projection listed on the website? (Circle the answer, 1point) Yes No

This image was downloaded from the Global Land Cover Facility (GLCF) at the University of Maryland. They use a file naming convention that provides useful information about the scene. The following is what the file name convention consists of:

    [satellite][sensor][path][starting row]_[ending row][acquisition date].img 
           Lengths: [1]         [1]     [3]        [3]                       [3]                     [8]

3. Provide the following information: (2 points)

   Date of acquisition: __________________________

   Path/Row: __________________________

4. A) Which band is the thermal infrared band of TM (2 points)? Band______ Spectral range: ______________ μm

B) How can you tell by looking at the imagery? (1 point)

C) What 2 types of terrain features appear warmest? (2 points)

D) What 2 types of terrain features appear coolest? (2 points)

Display and Link two viewers in ERDAS Imagine: Open TM band 1in a viewer and Fit to Frame. Now go to File New  2D View and open TM band 4 and Fit to Frame. The two viewers should be displayed side by side. With 2D View #1 (displaying TM band 1) highlighted (the upper frame of the viewer will show in yellow), go to the frame of 2D View #2 and click on the Spatially link icon . This will spatially link the two viewers. You can zoom in one viewer and the area you zoom to will be outlined in the other viewer. Likewise you can zoom to the same spatial extent and pan in one viewer and the other viewer will update to show the same extent. This is helpful when comparing two bands or datasets.

5. Using TM band 1 and TM band 4, examine the waterways surrounding Charleston. Comment on the differences you observe in the water surrounding the islands for each band and why you think those differences occur. (2 points)

6. Open the Inquire tool. Type in the these coordinates (600474, 3618299) into the X:,Y: boxes, respectively. The crosshairs will move to these coordinates and the images will pan to the area of the X, Y. Make sure your viewers are still linked. Examine the land located in this area of TM band 1, located just left of the barrier islands. Describe this area’s appearance in band 1. Now describe the same area using TM band 4. What is causing the feature to appear differently between the two bands? (2 points)

7. Use the Inquire tool to go to the area around the X, Y coordinates 589937, 3620917. The land should be located approximately between two rivers. Examine this land area for both TM band 1 and TM band 4. Describe and explain the differences in how and why they appear the way they do in each band. (2 points)

8. What are 2 advantages TM data provide for preparing a land use/land cover map of the area? (2 points)

9. What 2 disadvantages, or problems, might the TM data present? (2 points)

Part 2: SPOT Image Copy the entire folder SPOT6_1.5m_Ortho_Product_Bundle from G:/Fall-2015/G526/Lab06/. This is an original SPOT ortho product (with georeference) with all the information in the folder. Use ERDAS 2014, Open the images and the information in the folder (or use your textbook,internet) to fill the information below. (10 points)

Multispectral (MS) Band Name (e.g. red) Wave Length Pixel Size/Resolution 1 _________ _______________ _______________ 2 _________ _______________ _______________ 3 _________ _______________ _______________ 4 _________ _______________ _______________ Panchromatic (P) 1 _______________ _______________

10. Open the image IMG_SPOT6_MS_201212071020271_ORT_605187101_R1C2.JP2 in the folder of SPOT6_1.5m_Ortho_Product_Bundle\DS_SPOT6_201212071020271_E002N41_01983_1\PROD_SPOT6_001\VOL_SPOT6_001_A\IMG_SPOT6_MS_001_A

Answer the following questions:

A) Identify the number of rows and columns in this image (2 points): Rows ________ and Columns ______________ B) What’s the resolution of this image? (1 point)___________________

C) How many acres does this image cover? (Show your work, 2 points)

D) Date of acquisition (1 point) ___________________

11. You will use ArcGIS for this section. Open the “Part3.mxd” in the folder of Lab06. Identify the following features: (8 points)

A.

B.

C.

D.

E.

F.

G.

H.

12. There are many differences between SPOT 5 and SPOT 6. Compare the information about SPOT 5 and the information you found about the SPOT 6 images. Discuss the major differences between them (resolution, band number, etc.) (4 points)

Part 3. TM & SPOT Comparisons

You have now had a brief opportunity to examine Landsat and SPOT imagery. Use the available SPOT and TM images, the Lab06 handout, and your textbook for reference in answering the following questions.

13. Consider 2 advantages and 2 disadvantages of using such products versus, for example, aerial photographs. Speculate on and list some potential applications of Landsat TM and SPOT imagery respectively: (6 points)

14. Using a set of four criteria (spectral resolution, temporal resolution, thermal data, and geometric fidelity) contrast between TM and SPOT imagery. (e.g. what are the advantages and disadvantages of each, compared with the other) (4 points)

Bonus question: Use the resources from the internet, and get the information on Landsat 8. Compare Landsat5 TM and Landsat 8. What are the major differences between these two sensors? (Resolutions, applications?) Your answer must be specific to get full credit (3 points)

All you have to turn into blackboard for this week is the final image you created above.