I am trying to quantify change in water quality around storm drains before and after a rain event by quantifying imagery I have acquired. What I am thinking would be similar to an NDVI but for areas of dirty and clean water. I have been looking around for options on what to use to do this but haven't found anything successful. The end goal would be a quantification of a few images and then creating the equivalent of a dNDVI for the change over the days. Does anybody have recommendations for this?
I have tried change detection and compute change but have come up empty thus far
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I'm a newbie in RL so please forgive me if I ask stupid question:)
I'm working a DQN project right now and it's very similar to the simplest snake game. The game is wrote in js and has a demo (in which snake moves randomly). But since I don't know how to write js， I can't pass the action value to the game during trainng process, what I'm doing now is generating random game image and training the dqn model instead.
What I want to ask is that: Is it possible to do in this way? Can the Q(s,r) still converge? If it's possible, is there anything I should pay attention to? and do I need the episilon parameter anymore?
Thank you very much:)
I'd definitely say no!
The problem is that the agent will only learn from random decisions and can never try if a learned action produces maybe even more reward. So everything he learns will be based on the starting frames.
Further, the agent will, in your case, never learn how to handle his size (if it grows like in snake) because he will never grow due to the bad random decisions.
Imagine a child that tries to ride a bike and you lift it off the bike as soon as it has ridden one meter. It will probably be able to ride one or even more meters straight but will never be able to do turns, etc.
I am going to be working on self-chosen project for my college networking class and I just had a couple questions to help get me started in the right direction.
My project will involve creating a new "physical" link over which data, in the form of text, will be transmitted from one computer to another. This link will involve one computer with a webcam that reads a series of flashing colors (black/white) as binary and converts it to text. Each series of flashes will simulate a packet of data. I will be using OSX an the integrated webcam in a Macbook, the flashing computer will either be windows or osx.
So my questions are: which programming languages or API's would be best for reading live webcam data and analyzing the color of a certain area as well as programming and timing the flashes? Also, would I need to worry about matching the flash rate of the "writing" computer and the frame capture rate of the "reading" computer?
Thank you for any help you might be able to provide.
Regarding the frame capture rate, Shannon sampling theorem says that "perfect reconstruction of a signal is possible when the sampling frequency is greater than twice the maximum frequency of the signal being sampled". In other words if your flashing light switches 10 times per second, you need a camera of more than 20fps to properly capture that. So basically check your camera specs, divide by 2, lower the resulting a little and you have your maximum flashing rate.
Whatever can get the frames will work. If the light conditions in which the camera works are gonna be stable, and the position of the light on images is gonna be static then it is gonna be very very easy with checking the average pixel values of a certain area.
If you need additional image processing you should probably also find out about OpenCV (it has bindings to every programming language).
To answer your question about language choice, I would recommend java. The Java Media Framework is great and easy to use. I have used it for capturing video from webcams in the past. Be warned, however, that everyone you ask will recommend a different language - everyone has their preferences!
What are you using as the flashing device? What kind of distance are you trying to achieve? Something worth thinking about is how are you going to get the receiver to recognise where within the captured image to look for the flashes. Some kind of fiducial marker might be necessary. Longer ranges will make this problem harder to resolve.
If you're thinking about shorter ranges, have you considered using a two-dimensional transmitter? (given that you're using a two-dimensional receiver, it makes sense) and maybe have a transmitter that shows a sequence of QR codes (or similar encodings) on a monitor?
You will have to consider some kind of error-correction encoding, such as a hamming code. While encoding would increase the data footprint, it might give you overall better bandwidth given that you can crank up the speed much higher without having to worry about the odd corrupt bit.
Some 'evaluation' type material might include you discussing the obvious security risks in using such a channel - anyone with line of sight to the transmitter can eavesdrop! You could suggest in your writeup using some kind of encryption, a block cipher in CBC would do, but would require a key-exchange prior to transmission, so you could think about public key encryption.
I'm trying to estimate the hours required to build a group of 5 simple children's games in Flash. They will include such things as having kids drag and drop healthy food items into a basket; choosing the healthy and unhealthy food items by marking them in some way; etc.
I have no experience building games in Flash, but I have programmed in Flex and Actionscript. How many hours do you estimate for this project?
While your ActionScript background will help, I find Flash to be a VERY different experience from Flex and that proficiency in one environment does not translate well.
Is there a compelling reason not to use Flex? I think you would likely be much more efficient.
That aside, the mechanics of a simple drag and drop game could be put together fairly quickly. There are some good examples of basic drag and drop around. It can be a little tricky to get the mouse coordinates right if it is your first time.
That aside, there are other hidden costs you need to remember. Connecting infrastructure for example. Are the games connected in some way? Is there a running score or persistence that might imply authentication? Is there a story?
Also, If your forte is programming, don't underestimate that challenges of obtaining or creating art and sound assets.
Before you can estimate the time you'll need to break down what the games do. In other words, you'll need to write up very clear and definite requirements. You may even need to write up specifications. Once you've analyzed what the software should do, the estimate will also take a while - one part for example is figuring out whether there's already software that does what you want.
In my opinion, the best way you can possibly estimate a programming project, especially one in a technology you don't understand, would be to apply the Use Case Points methodology. Basically you break the project up into use-cases (what the users are trying to do) and actors (the user types and the system itself) and then list a few team and environment factors (how big an issue is code re-use, how familiar are you with the lanaguage, etc.) Studies have shown that it's more accurate for inexperienced developers than estimating based on features alone.
A google search for "use case points estimate" reveals many useful links. This explanation of the methodology seems to do a good job explaining how it works, though I've not read the entire thing. This worksheet will help when you're ready to start listing points.
I'm working on a "retro" motorbike game in flash, similar to the Road rash series on the mega drive and after having a long play with the sound sampling capabilities of flash I can't manage to find the "right" way to generate the noise.
I've been trying to basically change the frequency on a sine wave in line with the revs, so as the revs increase so does the frequency - it sorta works but sounds nothing like a real engine (I've been a biker for a while and I ride to work on my bike every day so I "know" what it should sound like :-p).
I'm not so much after a realistic sound, just somthing that sounds "okay", or good enough that most people playing the game wouldn't notice and be happy that the sound actually relates to the revs and speed as apposed to just a flat mp3.
I can't seem to search on google as I can't find the right words, "engine" just dilutes all of the results with game engines and what not.
The majority of articles I find also suggest using sampling - but there are 2 major issues with this:
Even though I have a bike and could record the sounds; recording samples of the rpm - say 15 if I do samples at 1000 intervals (my gsxr revs all the way to 16k :-p) I'd then have to also sample each one at various loads, i.e. 0mph, 10mph, 20mph, 30mph, 40mph as the engine noise varies greatly depending on load - which totals a whopping 80 samples - although I'm not sure if the load can be simulated somehow on top of the rpm samples?
All those samples add up to bytes that have to be downloaded before you can play.
One way I've found uses a mix of sampled engine sounds and synthesized tones. Get samples of an engine at a couple of different RPMs and use those for the base. Mix two samples based on the current RPM, e.g. if it's 1650 RPM, play a sample taken at 1500 RPM at 70% volume and a 2000 RPM sample at 30% volume. Modify the overall volume based on the throttle. Add a sine wave tone based on the RPM like you've done.
The technique is described in the paper Design of a Driving Simulation Sound Engine (PDF), which is about synthesizing engine (and other driving-related sounds) for a driving simulator. I found it by searching for sound synthesis "engine sound" (with "engine sound" in quotes. Motor sound effect synthesis has some discussion of synthesizing motor sounds in general, with instructions for the Pure Data environment.
Sonoflash have a library of code-based sounds (some for free), and may have something appropriate for you, or at least a starting point. Their 'machine propeller', for example.
I've tried Sonoflash as well, it's really good!
http://www.sonoflash.com/sounds/#EngineLight
This might be a sound you are looking out for.
I'm interested in building a 3D model of our solar system for web use (probably with AS3 and papervision) and have been looking into how I would go about encoding the planetary positions. My idea was to download the already calculated positions from NASA as calculating the positions myself seems a but overcomplicated. I'm not sure though whether I should use a helio centric or an earth centric encoding.
I wanted to know if there are any one with any experience in this. Which approach would be better? The NASA JPL website seems to have the positions of all the major bodies in our solar system as earth centric. I can see this becoming a problem later on though when adding Voyager and Mars Lander missions to the model?
Any feedback, comments and links are very welcome.
EDIT: I have a rough model running that uses heliocentric coordinates, but I haven't been able to find the coordinates for all planets in this format.
UPDATE:
I don't have a lot of detail to provide for know because I really don't know what I'm doing (from the space point of view). I wanted to get a handle on 3D programming, and am interested in space. The idea was that I would make a rough solar system simulator with at first all the planets and their orbiters (maybe excluding satellites at first). Perhaps include a news aggregator and some links to news/resources and so on. The general idea would be to allow people to click around and get super excited about going to the moon and Mars (for a starter).
In the long run I hopefully would be able to add in satellites and the moon missions (scroll back in time to the 70's and see the moon missions).
So to answer Arrieta's question the idea was not to calculate eclipses but to build an easy to approach, interactive space exploratorium, and learn some 3D and space related stuff on the way.
Glad you want to build your own simulator, but depending on what you want to do it may be far from an easy task. The simplest approach is as follows:
Download the JPL-DE405 ephemerides and the subroutines for retrieving the planetary positions (wrt Solar System Barycenter).
Request for timespan, compute the positions, and display them to the screen in a visually appealing manner
Done
Now, why would you want to do this? If you want to view the planet's orbits, that's it. You are done. If you want to compute geometric events (like eclipses, or line-of-sight, or ilumination) then you are in a whole different ball game. That's astronautics, and it is not simple.
Please be more specific. The distinction you make of "geocentric" or "heliocentric" coordinates really has no major difficulty involved. If you have all the states in heliocentric frame, you can compute the geocentric frame by simple vector subtraction. That's not the problem! The problems are a thousand more, but you need to be specific so we can provide more guidance.
JPL has provided high quality ephemerides for decades now, and we have a full team of brilliant people working on it. It is one of the most difficult things to get right!
Again, provide more details or check out other sources of information.
Please google "Solar System Simulator" (done here, at JPL) and see if it fulfills your needs.
Cheers.
It may be worth you checking out the ASCOM Platform (we also have a stack exchange site called ASCOM Answers).
The ASCOM Platform has several useful libraries for doing this sort of thing.
USNO NOVAS (Naval Observatory Vector Astrometry)
Kepler orbit engine
The USNO/NOVAS stuff was originally written in C and we've wrapped it up in .NET for ease of use from C# and VB.
As an added bonus (actually it's the raison d’être for ASCOM), the Platform makes it easy for you to control things like telescopes, it's used by Microsoft's World Wide Telescope for exactly that purpose. I tmight be a fun extension to your model to be able to point a telescope at things.
I'd probably start (well, I did a while back) with heliocentric coordinates and get a few of the planets up and running. But sooner or later you'll want to write a heliocentric-to-geocentric coordinate conversion routine, and its inverse. For some bodies, such as artificial satellites the geocentric coordinates will be easier to deal with.
You can use the astro-phys api to get a JSON formatted state vector for all the planets. It calculates them using JPL's de406 so it's pretty accurate and uses the solar system barycenter.
Although, if you know where the sun is relative to the earth and you're in a geocentric model, you can subtract the position of the sun from all of the bodies (including earth) to be heliocentric.