We collected reflectance data from leaves using the ALTA Spectrometer. This data is presented in Figures 1.1 to 1.10. The ALTA gives a readout of raw data for each wavelength as a voltage. Both of our schools recorded ALTA readings taken on a thick white sheet of paper, which was used as a control standard. The thick white paper standard reflects 90.95% of the light that hits it, for all wavelengths in the range measured by the ALTA. In the sample of ISD's recorded data, the second column is the ALTA readings from the white paper standard, the third and fourth columns are the ALTA readings from leaf #1and leaf #2, and then the fifth column is the average of those two leaves.

% Reflectance was calculated with the following formula:

% Reflectance = ( Sample Voltage - Dark Voltage ) ÷ ( Standard Voltage - Dark Voltage )

The Sample Voltage is the number reading on the ALTA spectrometer when a color
wavelength button is pushed.

The Dark Voltage is the number reading on the ALTA spectrometer when it was held
against any surface with no buttons pushed.

The Standard Voltage is the ALTA readings of each wavelength reflected from the
thick white paper.

Each day we recorded the color of the leaves using the GLOBE Plant Color Guide.
We are confident the ALTA measurements are good for most days. We were careful to hold the ALTA tightly against the background to keep outside light from entering the electric eye and changing the reading. We were careful to read the ALTA in the shade, not in bright sunlight.

2. GLOBE Green Down Summary

Both schools followed the protocols for GLOBE's Green Down activities. We used a GPS to find the latitude and longitude at our trees. The seasonal photos from early fall and late fall show the trees' changes in color until the leaves dropped. ISD stopped measuring well before Thanksgiving while MSSD stopped measuring after Thanksgiving break, when all our test leaves had dropped.

The Reflectance Profiles are graphs showing the % reflectance for each wavelength. The reflectance profiles for both of our schools seemed reasonable while the leaves were green. They show low blue, higher green, low yellows and red, and very high IR, which is what we expected. After the leaves changed colors, the profiles are more variable.

3. Tree Locations with Views in Four Compass Directions

We stood near our trees. Using a compass MSSD faced each direction, due N, S, E and W, and took photos. ISD students also took photos of the N, S, E and W sides of their trees

4. GLOBE Atmospheric & ALTA Reflectance Data

Graphs are included for environmental data and for nine wavelengths measured by the ALTA. The environmental data we collected at both of our schools included maximum daily temperatures, minimum daily temperatures, and daily precipitation. Maximum daily temperatures and minimum daily temperatures were used to calculate average daily temperatures.

At MSSD, we collected the data on 11 days, (Oct. 11-Nov.14) while at ISD, we collected data on 10 days (Oct. 11-Nov.6). We added the reflectance values from four leaves and used the average so the data would be manageable. In two places we did not have data for all 4 leaves, so the data is the average of only 3 leaves. The IR2 bulb on our ALTA burned out on almost the last day. At ISD, we averaged the data of our two leaves for our graphs.

After attempting to deal with the huge volume of data ourselves, we gave up and asked Dr. David Snyder of Gallaudet University to help us with visualization. He used a program called IDL to make graphs of all our data. We selected appropriate graphs. All of the original graphs can be viewed at: http://csc.gallaudet.edu/snyder/altaf02/altaf02.html.

We wish we had more ALTA measurements. We stopped at Thanksgiving break, and came back to find the leaves had fallen. Dr. Barry Rock looked at some of our graphs and was surprised that the green wavelength dropped to zero on November 11 in MSSD's data. It is unusual for green to drop to zero. The ALTA may have malfunctioned on that day. He also said the % of green reflectance should not be similar to the % reflectance numbers. These two wavelengths are usually in different ranges (for green, 5.0 to 10.0%; for blue 1.0-3.0 %). The blue is reasonable, but the green is low for all measurements during the fall. This is true for the data from both schools. We cannot explain this problem, but maybe the relative changes are still useful, since it seems like it was a problem the whole time.