quiz+homeworks

Question 1

If you had to design a map that allows you to measure distances across Alaska, what type of projection would you choose?

Answer 1

conical or planar

Question 2

Is NAD 83 a geographic projection? Explain your answer in one sentence.

Answer 2

NAD 83 is not a geographic projection rather it is a reference datum; NAD 83 defines a standard coordinate system and acts as a datum.

Question 3

If you had to design a map that allows you to measure distances within Uganda ( a country crossing the Equator), what type of projection would you choose, cylindrical, conical or planar? Justify your decision

Answer 3

cylindrical is best for north-south orientations

Question 4

What sensor do you think is in a phone camera:

Answer 4

CMOS

Question 5

How many satellites do you need at the very least to determine your position in space?

Answer 5

4

Question 6

Will a lens with a f-stop of 2.8 allows more, less, or the same amount of light to the sensor than a lens with a f-stop of 4?

Answer 6

more

Question 7

Why humans are unable to see wavelength of 1000 nm?

Answer 7

Humans are unable to see a wavelength of 1000nm because we only see in the visible spectrum which is between 400-700nm. Our eyes cannot see anything beyond that because our eyes are sensors that can only see a certain wavelength.

Question 8

Why most terrestrial animals, including humans, are not able to see wavelengths close to 100 nm? Explain in at most two sentences

Answer 8

blocked by the atmosphere

Question 9

Which wavelength has more energy: ultraviolet or infrared? Justify your answer with at most three sentences. You can use formulas

Answer 9

The wavelength that has more energy is the ultraviolet because the waves are smaller. Smaller wavelengths mean more energy because they have an inverse relationship,

Question 10

Explain in at most three sentences why the sky is mostly red at dusk?

Answer 10

Rayleigh scattering

Question 11

why do you think the electromagnetic spectrum of deciduous and
coniferous species is similar in the 0.4–0.7 μm range, and differs above 0.7 μm? Think about
what drives the reflectance in both regions

Answer 11

In the .4-.7 um range conifers and deciduous trees both contain chlorophyll which
reflects green explaining why they are at a similar reflectance. However as they approach the NIR portion of the spectrum they differ in reflectance, because unlike the visible spectrum in which 90% of reflectance comes from photosynthetic pigments, the NIR is much more affected by phenological traits (Ustin and Jacquemond 2020). Conifer needles are thicker and more compact which causes a lower spectral signature in the NIR while deciduous leafs are less compact and broad causing more reflectance in the NIR.

Question 12

)If you wanted to monitor the general health of all vegetation cover over the Pacific
Northwest region for several months, what type of platform and sensor characteristics
(spatial, spectral, and temporal resolution) would be best for this and why?

Answer 12

To monitor the PNW you would want a sensor with a spatial resolution where the
smallest unit captures individual trees. For temporal resolution 16 days like landsat would be fine as forests are known for slow changes. For spectral resolution you would want quite a few bands in order to differentiate the health characteristics of trees.

Question 13

)Hyperspectral scanners are sensors that detect and record radiation in several (perhaps
hundreds) of very narrow spectral bands. What would be some of the advantages of these
types of sensors? What would be some of the disadvantages?

Answer 13

Hyperspectral sensors have great spectral and radiometric resolution because of the
amount of bands they can detect and differentiate. However this leads to less spatial resolution and due to the amount of bands it can become redundant at some points. Because of the amount of bands they have, data storage can also be quite difficult.

Question 14

)Specify the molecules responsible for the majority of atmospheric absorption and
scattering?

Answer 14

The molecules responsible for the majority of atmospheric scattering and absorption are
Oxygen, Nitrogen, CO2 and H20 water droplets.

Question 15

You are tasked to VISUALY interpret a DTM image. You decide to change the default
position of the source of illumination from above the image to a new one located below the image. Do you think that changing the light location will help or confuse you in interpreting
the DTM?

Answer 15

The changing of lighting on a DTM from above the DTM as the default to below would
definitely not be helpful and most likely would just confuse. If the illumination was reversed, dark spots that usually indicate steep slopes and light spots that can show ridges would all be reversed and would end up looking like deep cannons where ridges should be. Overall
interpreting the image this way would be much more difficult.

Question 16

)The waves traveling throughout the atmosphere are affected by the particles within the atmosphere. Which portion of the electromagnetic spectrum is usually less affected by the path radiance, which means that less subsequent atmospheric corrections are needed? The answer can be broad, such as visible spectrum, but justified.

Answer 16

A wavelength less affected by path radiance would have an atmospheric window
meaning it is less prone to atmospheric absorption and scattering. The wavelength that might have the least atmospheric problems would be the visible portion of the spectrum. This is because visible light doesnt interact with as many molecules in the atmosphere as other
wavelengths. For example x-rays are unable to penetrate the earths atmosphere because they
interact with so many of the molecules in the atmosphere they would just be absorbed.

Question 17

What type of reflector is water? The answer should address the wavelength and the
geometry of the object reflecting energy

Answer 17

Water is a specular reflector meaning it acts like a mirror. This means the light bounces
off the light in a straight path and does not diffuse.

Question 18

Conversion of a spatial dataset from a coordinate system to another system is
accompanied by losses in accuracy. Depending on the data type, raster or vector, the losses
can be severe. Why do you think that the accuracy losses appear in the first place? To answer this question you could consider the way how the values within the vector or raster are computed during the transformation from one coordinate system to another. Figure 1.
Electromagnetic spectrum of some Earth features in visual and NIR wavelengths.

Answer 18

Raster data is calculated by assigning every cell a value. For example if the cell size is
30x30 and the units are defined as meters you would have a grid of 30 x 30 meter cells to make calculations from. Vector polygons track their attributes through assigned attributes but they can also calculate geometry based on the length or size of the line or polygon being displayed. To transfer vector data from one coordinate system to another you have to undergo a coordinate transformation which looks for relationships between the vectors in both systems. Basically you use a coefficient matrix of both vector data sets and find geometric relationships between both
which then allows for a coordinate transformation to occur. For raster data you are georeferencing points in order to convert points. This is often not easy to do and results in a bad conversion

Question 19

Q1 Which wavelength has less energy, blue light or red light? Justify your answer?

Answer 19

Red wavelength has the least amount of energy because its wavelength is the longest.

Question 20

Draw the electromagnetic reflectance curve of an average healthy and unhealthy forest.

Answer 20

You would draw the curve with a lesser reflectance in the green range because the forest is starting to become unhealthy

Question 21

Hyperspectral scanners are sensors which detect and record radiation in several (perhaps hundreds) of very narrow spectral bands. List two advantages and two disadvantages of these types of sensors?

Answer 21

Pros:
-can detect a wide range of wavelengths
-have better radiometric resolution and separate more wavelengths
Cons:
-have lower spatial resolution
-provide large amounts of data that can be hard to process.

Question 22

A sensor converts radiant energy to electrical energy. The entire system that participates in this conversion, namely the detectors, the optics, the electronics system, and the supporting elements, does not perform without errors. Therefore, the transformation of the radiant energy in electric energy is accompanied by the addition of noise to the recorded information. One of the parameters defining the performance of a sensor is the Signal – to – Noise ratio, which measures how much of the recorded signal is useable and how much is unwanted distortion or noise. What would the signal to noise ratio look like for a narrow band sensor (like most hyperspectral sensors) compared to a broader band sensor?

Answer 22

for a narrow band sensor you will have worse spatial resolution meaning a small IFOV which means you would have a small signal to noise ratio. For a sensor with a broad band range that has a large IFOV your signal to noise ratio would be large.

Question 23

Explain the difference between interior and exterior orientation parameters of a camera in one sentence.

Answer 23

The difference between interior and exterior orientation is the parameters they take. Interior orientation is the relationship between image plane and projection center while exterior orientation describes the position and angular orientation of the coordinate system of each photograph relative to the ground.

Question 24

What is the minimum overlap between two images such that stereopsis can be used for measurements?

Answer 24

the minimum overlap is 50%.

Question 25

Define digital number in the context of remote sensing and relate it to color depth (three sentences would suffice)

Answer 25

digital number in remote sensing refers to the value that is assigned to each pixel that corresponds to a color. The more digital numbers you have the more color depth you can obtain because of the amount of colors you can assign to a pixel.

Question 26

The conterminous United States is covered by 4 UTM zones. Is the previous statement True or False?

Answer 26

This statement is false. The 48 connected u.s states are UTM zones 10-19.