Lab - ELECTROMAGNETIC RADIATION PRINCIPLES

This exercise provides an introduction to using a Global Positioning System (GPS) receiver to obtain coordinates and create a point shapefile. GPS is a system consisting of a network of satellites that orbit ~11,000 nautical miles from the earth in six different orbital paths. They are continuously monitored by ground stations located worldwide. The satellites transmit signals that can be detected with a GPS receiver. Using the receiver, you can determine your location with great precision through the trilateration (not triangulation!) of signals from at least 3 satellites, getting a distance from the difference between time measurements.

Although the system is very sophisticated, and atomic clocks are used by the satellites, there are multiple sources and types of errors involved in finding your location. As the GPS signal passes through the charged particles of the ionosphere and then through the water vapor in the troposphere, this causes the signal to slow a bit, and this creates the same kind of error as bad clocks. Also, if the satellites that are in your view at a particular moment are close together in the sky, the intersecting circles that define a position will cross at very shallow angles. That increases the error margin around a position. The kind of GPS receivers we will be using provide about 10 meter accuracy (which may be reduced to under 3 m if differential corrections like WAAS are used), depending on the number of satellites available and the geometry of those satellites.

In this exercise we are going to collect the coordinates of some set of campus features using either the GPS units or your phones, generate a few shapefiles of those features, and then use the shapefile to make a map. The goals for you to take away from this lab:

• How to use your selected platform to collect data
• How to export that data
• How to view that data in GIS software

Outline:

You are answering the questions (laid out in the word doc above and also included in the tutorial below) as you work through the lab. Use full sentences as necessary to answer the prompts, and submit it to blackboard when done.

1. For each of the following, provide the frequency or wavelength as appropriate. Also, specify the region of the electromagnetic spectrum (e.g., ultraviolet, blue, green, red, near-infrared, mid-infrared, thermal-infrared, microwave) (Note: 1 Hz = 1 cycle/sec = 1 sec -1; light speed (C) is at 3×108 m/sec; 1m = 106 μm). (4X2=8 points)

(a) Wavelength = 0.460 μm Frequency =

Spectral region =

(b) Wavelength =

Frequency = 3.50 x 1013 Hz Spectral region =

2. If we compare the radiation described in 1(a) and 1(b) above, which one has the higher energy content per quantum (or photon) (show computations for each)? In one sentence, explain the implications of this fact for remote sensing (10 points).

3. We may think the Red-hot object as an 800k blackbody.

(a) What is the total amount of energy emitted by it per unit area?

(b) What is the dominant wavelength of Red-hot object?

(c) Compared to the Earth which has a dominant wavelength of 9.66 µm, which one produces more radiant exitance? (10 points)

4. Read the image below which illustrates different colors or vividness of forests close by and far away. Please explain it according to what we have talked about in lecture class. (Hint: optical effects of atmospheric haze) (3 points)

5. Some streetlights are deliberately manufactured to provide illumination with a reddish color, can you suggest why? (3 points)

6. The Earth’s land surface reflects about three percent of all incoming solar radiation back to space. The rest is either reflected by the atmosphere, or absorbed and re-radiated as infrared energy. The various objects that make up the surface absorb and reflect different amounts of energy at different wavelengths. The magnitude of energy that an object reflects or emits across a range of wavelengths is called its spectral response pattern or spectral reflectance curve.

   Table 1 gives you the spectral reflectance (%) for three different types of surface covers measured by a sensor with 24 bands (the mid value of band wavelength is given). (25points)

(a) Based on these data, construct spectral reflectance curves for these targeted objects (on the last page). These curves will help you answer questions 4b-4c. Please use a pencil and draw the lines clearly (10 points)

(b) Which band is better for discriminating vegetation from water: Band 6 versus Band 10? Why? (5 points)

(c) Which band is better for discriminating barren land from water: Band 1 versus Band 6? Why? (5 points)

(d) Which band is better for discriminating these three surface covers: Band 12 versus Band 24? Why? (5 points)

| Band | Mid value of bandwidth

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| Reflectance (%) | 78 | | | | | | | | | | | | | | | | | | | | | | | | | | | | ————————- | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | | | 75 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 72 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 69 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 66 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 63 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 60 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 57 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 54 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 51 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 48 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 45 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 42 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 39 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 36 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 33 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 30 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 27 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 24 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 21 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 18 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 15 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 12 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 9 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 6 | | | | | | | | | | | | | | | | | | | | | | | | | | | | 3 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 17 | 20 | 23 | 26 | 29 | 32 | 35 | 38 | 41 | 44 | 47 | 50 | 53 | 56 | 59 | 62 | 65 | 68 | 71 | 74 | 77 | 80 | 83 | 86 | 89 | 92 | | Wavelength (100 × µm) |