The purpose of this resource is to select 15 km x 15 km Land Cover Sample Sites. Educational levels: Primary elementary, Intermediate elementary, Primary elementary, Intermediate elementary

The GLOBE Program, University Corporation for Atmospheric Research (UCAR)

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Digital Library for Earth System Education

GLOBE® 2005  Site Selection - 1 Land Cover/Biology
Learning A
ctivities
A
ppendix
W
elcom
e
Introduction
Protocols
Sample Site Selection  
and Set-Up
Overview
You will choose multiple Land Cover Sample 
Sites within your 15 km x 15 km GLOBE Study 
Site. These sample sites will serve as the locations 
where you take land cover measurements. You 
will need these measurements to create your land 
cover type map. Preferably, you should collect 
at least one Sample Site for each class of land 
cover that you observe in your Study Site. You 
will need data from additional Sample Sites to 
perform an accuracy assessment to validate the 
land cover map you created. You may also decide 
to establish additional Sample Sites whenever you 
are unsure or curious about the land cover in any 
area. Some of these sites you may only visit once. 
In other sites, you may want to study changes in 
vegetative growth throughout the seasons so you 
may visit these sites frequently. The following 
provides instructions on how to select and setup 
these Sample Sites.
Instructions
ALL Land Cover Sample Sites within the 
GLOBE Study Site must have the following 
characteristics:
• Homogeneous – the same MUC class 
throughout.
• 90 m x 90 m in size. 
• Oriented in the cardinal directions  
See How to Lay-Out Land Cover Sample Site.
All Land Cover Sample Sites are visited at least 
once but can be visited multiple times during 
different times of the year, or different years, in 
order to conduct studies on changes in biomass 
over time. 
For instance, instead of taking measurements 
only ONCE during peak growth, measurements 
can be taken TWICE a year, every year. Your 
semiannual visit should occur once during peak 
growing season and once during the least active 
season (summer vs. winter, rainy season vs. 
drought, etc.). If you have no temperature or 
rainfall-dependent seasonality in your region, take 
measurements only once a year.
You should permanently mark any trees and 
shrubs that you measure, since you will return 
to measure the same ones each time. When you 
enter your data, make sure that you enter the tree 
or shrub heights and circumference in the same 
order each time. This way, you will be describing 
changes/growth in the same tree or shrub when 
you report your data.
How to Lay-Out a Land Cover 
Sample Site
Select a 90 m x 90 m homogeneous area. Use your 
Landsat TM images and/or your local knowledge 
to help you locate candidate sites. An area that is 
homogeneous has the same MUC class throughout 
the site.
In order to determine if your site is at least 
90 m x 90 m in the cardinal directions, pace out 
GLOBE® 2005 Site Selection - 2 Land Cover/Biology
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GLOBE® 2005  Site Selection - 3 Land Cover/Biology
Learning A
ctivities
A
ppendix
W
elcom
e
Introduction
Protocols
(refer to Pacing in Investigation Instruments) 90 m 
from one of the corners of the site. Pace in two 
directions, either North or South AND either East 
or West. This will give you an estimate of where 
two more corners are. Estimate the location of the 
fourth corner. If the entire area is homogeneous, 
the site is appropriate. (For example, if a 30 m x 
30 m area within a forested site has less than 40% 
canopy cover, the site is not homogeneous.)
Name the site. The Site Name should be unique 
and identify the site unequivocally. It should not 
be frivolous.
Note: Areas that look the same on the Landsat 
image may not be homogeneous and may not have 
the same MUC class throughout the site. You must 
make the final determination at the site.
How to Take Biometry Measurements
Once you have established that the site is a 
90 m x 90 m homogeneous area aligned in the 
cardinal directions (N, S, E, and W), you need 
to determine its MUC Level 1 class. Biometry 
measurements are taken in the center 30 m x 30 m 
pixel of the 90 m x 90 m Land Cover Sample Site. 
Students take some of the biometry measurements 
as they pace along a diagonal(s) of the center 
pixel.
The amount and types of biometry measurements 
are determined by the information you need in 
order to classify the site to the most detailed 
level of the MUC System. See Figure LAND-
SS-1 for examples of what measurements might 
be appropriate in specific types of land cover 
sites. Canopy cover and ground cover should 
almost always be taken in a natural site. These 
measurements will help you determine the Level 1 
MUC class. Tree and shrub species identification, 
as well as tree, shrub and/or graminoid height, 
will help you determine the higher level MUC 
classes. Tree and shrub circumferences and 
graminoid biomass are helpful to scientists 
and to your students when they are studying 
changes in biomass over time or making specific 
classifications using satellite imagery. Refer to the 
Biometry Protocol for detailed instructions. 
If the site is not visible from the road/path, record 
the related compass directions and number of 
paces needed to reach the corner or center of the 
site from the road/path. You can mark the corners 
or the center of your site for future visits. While 
this is not necessary, you may choose to. If there 
is a chance you may return at a later date, you 
should mark the center of the 90 m x 90 m site 
so you can quickly find it.
Take Biometry measurements following the 
Biometry Protocol. This will involve doing the 
following:
• Mark the center of the 90 m x 90 m site 
where you will be taking measurements. 
See Figure LAND-SS-2.
• Divide the students into four groups. 
Assign each group a direction to walk 
and take canopy and ground cover 
measurements along a diagonal from 
the center. Using a compass, assign each 
group one of the following directions: 
NE (45˚), SE (135˚), SW (225˚), and NW 
(315˚). 
• Each diagonal measures 42.4 m, each 
group should walk half of a diagonal or 
21.2 m.  
• If you choose, put markers at each corner.
• Combine the data from each group in 
order to choose your final MUC class, and 
submit the data to GLOBE. 
1
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2
Validation Data
S
tu
de
nt
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ap
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la
ss
ifi
ca
tio
n
MUC
71
MUC
71
MUC
811
MUC
92
MUC
0222
MUC
1222
MUC
91
MUC
93
MUC
824
MUC
4223
Column
Totals
MUC
811
MUC
92
MUC
0222
MUC
1222
MUC
91
MUC
93
MUC
824
MUC
4223
Row
Totals
GLOBE® 2005  Site Selection - 4 Land Cover/Biology
If you choose to spend additional time in the field 
or would like to practice additional pacing and 
compass skills, here is one way to mark the center 
pixel of a 90 m x 90 m Land Cover Sample Site. 
See Figure LAND-SS-3.
• Place a marker where you want one corner 
of your center pixel to be. 
• Use your compass and measuring tape to 
move 30 meters in a cardinal direction 
(North, South, East, or West). Place a 
second marker at the end of this transect. 
This forms side one.
• From the second marker, move 30 meters 
perpendicular to side one. Place a third 
marker at the end of this transect. This 
forms side two.
• From the third marker, move 30 meters 
perpendicular to side two and parallel to 
side one. Place a fourth marker at the end 
of this transect. This forms side three.
Figure LAND-SS-3: Marking the Center Pixel
90 m
eters
90 meters
Side Two
(30 m)
21
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Side Four
(30 m)
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S
ide Three
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Homogeneous Land Cover N
• From the fourth marker, move 30 meters 
toward your original marker. If this 
transect ends within 2 to 3 meters of the 
original marker, you are successful. If you 
are farther away from the marker, check 
your compass bearings for each side, check 
the length of each side, and try again.
• Establish the center of your square by 
pacing the diagonal transects of the square 
and placing a marker where the two paths 
intersect. You may use string to make these 
diagonals. Also note that the two diagonals 
should be of equal length.
GLOBE® 2005  Site Selection - 5 Land Cover/Biology
Learning A
ctivities
A
ppendix
W
elcom
e
Introduction
Protocols
Frequently Asked Questions
1. What if our homogeneous site is not  
90 m x 90 m?
If your site is not homogeneous, you will need to 
find another site that is at least 90 m x 90 m where 
the land cover is the same throughout.
2.  In the 1997 GLOBE Teacher’s Guide, the 
Land Cover/Biology Investigation talks about 
Qualitative and Quantitative Land Cover 
Sample Sites and Biology Study Sites, but not 
in this version. Why? How has the chapter 
changed?
In this 2003 version of the Teacher’s Guide, we 
removed the terminology for the different types of 
Land Cover Sites. In the 1997 version, biometry 
data were collected and entered in the GLOBE 
database only for Quantitative Land Cover Sample 
Sites and Biology Study Sites for Closed Forest, 
Woodland, and Herbaceous Vegetation (MUC 0, 
1, and 4). Now biometry data can be collected for 
most MUC classes. It is up to teachers and students 
to decide how much biometry data should be 
collected. We would like you to collect ground and 
canopy cover data along the entire length of both 
diagonals within the 30 m x 30 m center area of 
your 90 m x 90 m site.
3. What should we do if we have already 
established a Biology Study Site, a permanent 
Land Cover site to which we return year after 
year, but it is not a  
90 m x 90 m homogeneous area?
If the area around the Biology Study Site is 
homogeneous with your old Biology Study Site, 
you can use it, simply expand the area so it is 
90 m x 90 m around your center. This will now be 
simply called a Land Cover Sample Site. You can 
still visit it repeatedly and take measurements in it. 
However, if the area around your old Biology Site 
is not homogeneous, your data will be difficult to 
compare with satellite images. There is a certain 
amount of error in the GPS readings, so even if 
you are in the center of the site, the reading could 
actually place you anywhere in the 90 m x 90 m 
area surrounding the center. You will need to find 
another suitable site. You could still use the old 
Biology Study Site for practice.
4. What can I do in an urban area?
You can perform the full investigation. 
In an urban area, most of the sites 
will be developed rather than natural 
classes. This is fine, so collect as many Land Cover 
Sample Sites as you can. These are very important 
to scientists because urban land cover types are 
difficult to identify and distinguish in Landsat 
TM imagery.
5. What if a pond runs through our 90 m x 
90 m area?
If a pond or stream runs through your 90 m x 90 
m site, it is not homogeneous and is not a valid 
site. Try to move the site over to exclude the pond 
and make it homogeneous.
6. What if a stream runs through our site?
If the stream is so small (narrow) that it doesn’t 
alter the MUC class of any 30 m x 30 m part of 
the site, it is ok. If not, move the site to exclude 
the stream.
7 What if the site is on private property?
If the site is on private property, please get 
permission before entering the area.
8. What do I do if my Land Cover Sample 
Site has experienced catastrophic change 
since my last visit? 
If your site experiences catastrophic change (i.e. 
fire, wind damage, hurricane, tornado) between 
visits, please describe this in the metadata 
section and do the measurements on any 
existing vegetation (trees, graminoid vegetation). 
Scientists are very interested in rates of recovery 
or succession in such sites. If the 90 m x 90 m site 
is homogeneous, please do the Land Cover Sample 
Site Protocol.
9. There is a small clearing about 10 m x 10 
m in area in our forested site. Is the site still 
homogeneous?
Yes, if the 30 m x 30 m area that surrounds the 
clearing has the same MUC class as the rest of 
the site.
 


Sample Site Selection and Set-Up

http://www.globe.gov/tctg/land_prot_siteselect.pdf?sectionId=207

Sample Site Selection and Set-Up

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