2011-2012 Modules and Units
Sunday, April 15, 2012
Monday, February 13, 2012
The shortish answer: Because healthy green plants have a high reflectance value in the near-infrared (NIR) part of the spectrum. We can’t see NIR light normally, but the sensors in our cameras can. (Landsat and other imagers also ‘see’ NIR, as well as several other slices of the EM spectrum.)
Computers display color using three different channels, red, green, and blue. When we look for vegetation in TwinCam or Landsat imagery, we use MultiSpec to ‘map’ the NIR channel from the camera or sensor into the red channel that the computer displays. Since we have now used the red channel to show NIR data we will map the red and green channels from the camera to the green and blue channels on the computer, respectively. (We don't use the blue band here, so it isn't mapped to a channel.)
Vegetation looks red because the red pixels are showing the NIR, which again has a high reflectance value. (Remember that percent reflectance is simply the percentage of incoming sunlight that is being reflected back by the object in the image.) The green pixels on the computer are showing the red information from the camera. Plants absorb red light so these values are low. That means there won’t be much green in the vegetation on the screen. The blue pixels on the computer show the green information from the camera. Vegetation reflects more green light than it does in red or blue, so those values are relatively high. So, on the computer screen:
- Red pixels show NIR information (high reflectance in vegetation)
- Green pixels show Red information (low reflectance in vegetation)
- Blue pixels show Green information (moderate reflectance in vegetation)
- (blue information is discarded)
Below is a graphic representation of the channel mixing process using actual imagery from two cameras - one capturing visible light and the other capturing a slice of the near-infrared around 800 nm. (This is what we do when we process TwinCam imagery.)
A bit more information that you may find helpful:
Our TwinCam cameras have a sensitivity 8 bits per pixel - that is 28 or 256 integer values for each of the red, blue, and green channels. The values represent a grayscale range from 0-255, with 0 corresponding to 0% reflectance (black), and 255 responding 100% reflectance (white). This is called the Radiometric Resolution of the camera or sensor.
Based on the reflectance curve in the graph above, a typical pixel of healthy green vegetation might have the following values:
Normally, we would display the red, green and blue pixels values into the corresponding red, green and blue channels and our leaf would look greenish. However, we are interested in the NIR information, and to see those values we need to map that information to one of the other channels.
Tuesday, January 10, 2012
Designing High Quality PBL
I emphasize the term ‘high quality’ PBL for two reasons. First, many educators still equate PBL with ‘doing projects,’ ‘hands on’ learning, or ‘activities.’ This is an industrial holdover from the time when projects were designed as an antidote to lecture or a respite from seat time, as a culminating opportunity for students to finally demonstrate what they had learned during the year, or even as a simple reward for having endured tedious instruction.
PBL is a far more evolved method of instruction. Well-executed PBL begins with the recognition that, as in the real world, it’s often difficult to distinguish between acquiring information and using it. Students learn knowledge and elements of the core curriculum, but also apply what they know to solve authentic problems and produce results that matter. Students focus on a problem or challenge, work in teams to find a solution to the problem, and often exhibit their work to an adult audience at the end of the project. Most important, PBL emphasizes carefully planned assessments that incorporate formative feedback, detailed rubrics, and multiple evaluations of content and skills.
But even with a method, mediocre PBL is still possible (and too prevalent). Simply turning students loose on a problem or question, putting them in groups, and having them do an exhibition or PowerPoint at the end of two weeks, does not meet the criteria for ‘high quality.’ This is especially true if innovation is our goal. Fostering innovation is a complex, challenging task that requires a teacher to do many things all at once: Refocus learning on the student; teach critical content; develop and assess global-age skills; offer constant opportunity for deep thinking and reflection; and reward intangible assets such as drive, passion, creativity, empathy, and resiliency. High quality PBL can offer students that complete experience, but it doesn’t happen automatically.
High quality PBL begins with a consistent, considered project design. Teachers move through a design process based on specific principles backed by proven methods and practices. Taken as a whole, this methodology allows teachers to conceive and implement a coherent problem-solving process that brings out the best work in students and addresses the key standards in the curriculum. Slight variations exist among practitioners, but there is general agreement on these methods. In my work, I use seven design principles. Each principle represents a point—or fault line—at which the project can be made more powerful and engaging, or less so:
- Identify the challenge. At the core of PBL lies a meaningful, doable challenge. This means that projects start with a powerful idea, an authentic issue, or a vital concept. The challenge must then be defined so that it aligns with the objectives of the course, but not so narrow that it doesn’t demand innovation and insight.
High quality tip: Design projects that matter. A project that gives students an opportunity to contribute to their community or prepares them for life will invite their best efforts and whole-hearted participation. Generally, if projects originate from a laundry list of standards, they lack a big idea to power the project. There must be a reason to learn beyond covering the curriculum.
- Craft the Driving Question. Your intention drives a project. What is the deep understanding that you want students to demonstrate at the end of the project? There is a proven process for turning a challenge into a driving question that captures the intent and depth of the project.
High quality tip: Make the problem relevant. An effective Driving Question taps a deep level of motivation. For example, a social studies team shifted their question on a Depression-era project to get at deeper lessons from the 1930’s that resonate today:
“What can we learn from the 1930’s?” to “How important is self-reliance in today’s world?”
- Start with Results. PBL mimics the ‘plan backwards’ approach recommended by many educators. Given that PBL focuses on problem solving, innovation, and ‘fuzzy’ goals, it is imperative that you design both the knowledge acquisition as well as the process of learning. Think of yourself as more of a coach than a teacher. Your job is to put together a game plan for high performance.
High quality tip: Think beyond normal lesson planning. Questions that should come up at this stage: What protocols and peer methods will you use to encourage reflection and deep thinking? How will you organize your teams? What evidence will you require to reward innovative thinking?
- Build the Assessment. The key to high quality PBL assessment is to view content as one of several outcomes that will help students become more skillful, be reflective about their capabilities, and prepare them for post secondary success. This means designing evaluations and formative assessments in five areas: (1) global-age skills; (2) conceptual understanding; (3) personal strengths or habits of mind; (4) innovation and creativity; and (5) critical content.
High quality tip: Distinguish assessment and evaluation. Assessment is a constant tool, used to improve performance and support growth over time; evaluation is the final score. Formative assessment is essential to PBL. Use it regularly throughout a project to improve performance. Assess skill development as well as content mastery.
- Enroll and engage. Starting right is the key to success at the end. This includes helping students connect their interests to the question or problem, and organizing teams for effective performance by establishing norms and clear benchmarks.
High quality tip: Use a Critical Friends or tuning protocol to have students refine the question or the project. This is an excellent time to incorporate student voice. If you need a copy of the protocol, download the Top Ten PBL Tools at www.thommarkham.com.
- Focus on quality. High quality PBL relies on teams that demonstrate commitment, purpose, and results, similar to the organizational goals of high performing industries. To do this, let go of the notion of ‘groups’ and move to the language of teamwork. Allow plenty of time for preparation, drafting, and refinement of products, presentations, and skills.
High quality tip: Facilitate deep thinking. Teach your students the tools of inquiry and require the teams to practice the skills of dialogue, visible thinking, peer evaluation, and critique.
- End with Mastery. PBL is a non-linear process that begins with divergent thinking, enters a period of emergent problem solving, and ends with converging ideas and products. A good PBL teacher manages the work flow through the chaos of the project, but also closes the project by giving students every opportunity and support necessary to experience a sense of mastery and accomplishment.
High quality tip: Reflect. Take two days to review and reflect on the project. Reflect on accomplishments, and evaluate the project against criteria. Was the Driving Question answered? Was the investigation sufficient? Were skills mastered? What questions were raised? The project debrief improves future projects, as well as teaching students the cycle of quality improvement.
How can we sum this up? PBL promises more engaging school work and a shift in the culture of learning that should be visible in the form of more satisfied, higher performing, and more innovative students. But it does require a systematic approach that fully engages students, offers a potent blend of skills and intellectual challenge, and prompts or awakens a deeper curiosity about life. From that standpoint, PBL is still a work in progress.
Thom Markham, Ph.D., is a psychologist and school redesign consultant who assists teachers in designing high quality, rigorous projects that incorporate 21st century skills and the principles of youth development. He is the primary author of the Buck Institute for Education’s Handbook on Project Based Learning and the author of the forthcoming Project Based Learning Coach’s Guide. He may be reached through his website at www.thommarkham.com, where visitors can download the Top Ten Tools for PBL.