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### Re: Remote Sensing C

Posted: **May 8th, 2011, 7:36 pm**

by **The Eviscerator**

Could you give an example? I don't think I've ever come across a question like that.

I found some info on wikipedia about calculating spatial resolution, but it was through trig, and using wavelength, and the diameter of the lens' aperture.

I'll post the question after I see my state test (I don't remember it now). This should be in a couple days (Wednesday?).

Also, what are the units for spatial, spectral, radiometric, and temporal resolution?

### Re: Remote Sensing C

Posted: **May 8th, 2011, 8:05 pm**

by **bwy**

Also, what are the units for spatial, spectral, radiometric, and temporal resolution?

Spatial- units of length, like m or in. Or it could be square meters, I guess

Spectral- basically how many different wavelengths it can detect (multi-spectral has higher spectral res)

Radiometric- units of intensity, measured in bits usually because it's a computer recording the light intensity, like 256 bits

Temporal- time, like s or days (it's how often the satellite can sample the radiation)

### Re: Remote Sensing C

Posted: **May 11th, 2011, 8:12 pm**

by **haverstall**

Eviscerator, have you gotten your test back yet? Also, I thought you couldn't get states tests back?

### Re: Remote Sensing C

Posted: **May 11th, 2011, 8:54 pm**

by **The Eviscerator**

Eviscerator, have you gotten your test back yet? Also, I thought you couldn't get states tests back?

Right, thanks for reminding me. I just got the test back today actually. In NC, the state director lets the teams that are going to nationals look at the state tests.

Here is the afore-promised question (as you can see, my memory of the question was a bit flawed):

If a satellite-based pushbroom sensor has a row of 9,000 CCD cells aligned perpendicular to the satellite's motion, and the swath width is 270 kilometers, what is the ground sampling distance (spatial resolution) in meters?

And I just realized how to do this question *facepalm* so I'll explain it if anyone needs me too.

Okay, here is a hard one: If the satellite in the previous question (the one above) is in a polar, sun-synchronous orbit at an altitude of 705 kilometers, how many minutes and/or seconds of its orbital ground track would be covered by a square image area covering 270km x 270km?

If anyone can explain this that would be great, since I have no idea how to do it. I'll post what the answer is after you guys try to figure it out.

The other questions we got wrong were stupid mistakes... Really stupid mistakes... *facedesk over and over again*

### Re: Remote Sensing C

Posted: **May 11th, 2011, 9:23 pm**

by **haverstall**

Awesome. I never come across these types of questions before.

I don't really know about the first one, but I think I can make an educated guess about the second one.

A polar sun-synchronous orbit is 100 minutes long (AQUA is an example) and the circumference of the Earth is 6378 km (info from wikipedia). Now some simple division: 270/6378 should give the percentage of the Earth's circumference that the 270km square covers, and multiply by 100 minutes get you...4.23 minutes, or approx 254 seconds.

Don't explain question 1 just yet; I want to do some studying on my own to see if I can figure it out.

Btw, how did you do in Remote Sensing at your state competition?

EDIT 1: So, I'm pretty much coming up blank with the first question. Is it just 270km/9000? Meaning the answer is 30 meters?

### Re: Remote Sensing C

Posted: **May 12th, 2011, 11:46 am**

by **winneratlife**

If a satellite-based pushbroom sensor has a row of 9,000 CCD cells aligned perpendicular to the satellite's motion, and the swath width is 270 kilometers, what is the ground sampling distance (spatial resolution) in meters?

And I just realized how to do this question *facepalm* so I'll explain it if anyone needs me too.

If you imagine the pushbroom, you have 9000 cells lined up. Width is 270000 meters.

Each cell encompasses 30 meters.

### Re: Remote Sensing C

Posted: **May 12th, 2011, 2:00 pm**

by **The Eviscerator**

The answer to the first question is 30m. It is that simple.

Now as for the second question, you are not even close haverstall. I'll give you some more time to think about it and try it again until I post the answer on the answer key.

We got 6th at our state competition, but we only lost to first by 6 points, and we made a bunch of stupid mistakes, so we could've easily gotten first. Hence the repetitive facedesk.

### Re: Remote Sensing C

Posted: **May 12th, 2011, 9:05 pm**

by **haverstall**

Ok, so was looking at this question again, and realized that maybe instead of times, it's talking about minutes and seconds as in degrees. So is the answer 60 minutes?

### Re: Remote Sensing C

Posted: **May 12th, 2011, 9:13 pm**

by **The Eviscerator**

Actually, haverstall, I looked at what you did the first time, and you did everything right, but you accidentally used the Earth's radius instead of diameter, so you were off by a lot. The answer is 40 seconds.

### Re: Remote Sensing C

Posted: **May 12th, 2011, 9:37 pm**

by **haverstall**

fffffffffffffff....i'm feeling like the dumbest person on this planet.

yup, it's 0.67 minutes or 40 seconds. Good to know I had the right process.