Spectrum Technologies FIELDSCOUT TCM 500 NDVI User manual

TCM 500 NDVI
Turf Color Meter
PRODUCT MANUAL
Item # 2975NDVI
®
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Contents
General Overview 3
Computer Interface/Changing the Battery 5
Initial Startup 6
Identifying the Correct Com Port 7
Connecting to a GPS Unit 8
Keypad Operation 11
Standard Reading Mode 14
Field Scout Software Toolbar 16
Meter Settings 18
Data Files 19
Meter Indexes 20
Specifications 22
ERROR messages 23
Appendix 1: Time Zone Corrections 24
Frequently Asked Questions 25
Service and Support 26
T-handle 10
Adjusting the Grass Index 21
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General Overview
Turf grass quality is visually evaluated by human
assessors based on a scale of 1 (poorest, the grass is dead)
to 9 (ideal, the grass is of outstanding quality) using a
common assessment method. A rating of 6 or greater
indicates adequate turf quality. Because this evaluation
practice is subjective, individual biases are inevitable and
lead to some level of inconsistency, even among the most
highly trained observers. This variability led to the need
for a more objective evaluation technique.
To answer this need, researchers have developed the
Normalized Difference Vegetative Index (NDVI). The
Field Scout TCM 500 “NDVI” Turf Color Meter
measures reflected light from turf grass in the red (660
nm) and near infrared (850 nm -NIR) spectral bands.
Because chlorophyll absorbs the red band (660 nm) of
incoming radiation, the reflectance at that wavelength is
relatively low due to the strong absorption of the light by
the plant pigments. The high reflectance in the NIR (850
nm) band is caused by the cellular structure of the plant
leaves, particularly the spongy mesophyll leaf structure.
The meter also provides the user with the option of
viewing a Grass Index calculated from NDVI. This index
can be adjusted to match the user’s evaluation of that
field.
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Features
• A measuring target approximately 3 inches (7.6 cm) in
diameter.
• Consistent internal light source that negates the effects
of sunny versus cloudy conditions.
• Red & NIR data is presented in three forms: Percent
reflectance (0.0 to 99.9) of Red and NIR, NDVI (0.000
to 1.000), and Grass Index (ie. 1.00 to 9.00).
• GPS/DGPS can be used - requires GPS/DGPS cable
(item 2950CV5).
• A running average is calculated and displayed as
multiple readings are taken.
• Data is stored in comma-delimited text files. They can
be opened and processed with any spreadsheet,
graphing, statistical, or word processing program.
• Optional T-handle extension to allow measurements to
be taken while standing.
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Computer Interface/
Changing the Battery
Software Installation
Insert the CD for Field Scout software into your PC’s disk
drive. If auto-start is not enabled on your computer, select
Run from the Start menu and type D:\Setup.exe
(Substitute the appropriate drive letter for your CD drive).
Click OK and follow the instructions on the screen.
The meter’s data port can be accessed by removing the
plastic screw to the left of the handle. It is through this
port that the meter is connected to either a PC or to a GPS
unit. The meter must be turned off before attempting
communication with the software.
Connecting to a PC
The Field Scout software comes with a black PC interface
cable. This cable connects to the USB port of your com-
puter and to the meter’s computer port. The meter’s con-
figuration can be modified by clicking on the Meter Set-
tings button (see Meter Settings, p. 18). The Com Port,
Meter Type, Download, Clear Memory and Meter Set-
tings buttons are explained in the Main Toolbar section (p.
16). Note: Prior to 2014, the meter was shipped with a
gray cable that connected to a 9-pin serial port. This cable
will still work but may require a USB-to-serial adapter.
Changing the battery
The battery compartment is accessed by removing the 4
phillips head screws on the underside of the meter and re-
moving the bottom plate. The TCM 500 meter is powered
by a 9-V battery.
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Allow the temperature of the TCM 500 meter to
equilibrate with the turf environment prior to sampling.
When the TCM 500 meter is first turned on, the battery
strength (Battery at __ %)will appear on the LCD. The
available battery power percentage assumes alkaline
batteries are being used. If rechargeable NiCd batteries
are installed, the available battery power will be more than
displayed. If the data logging option has not been
enabled, the unit will then proceed to the standard reading
mode.
In order to record data and global positioning system
(GPS) coordinates, the data logger must first be enabled
through the software (See p. 18). If the data logger has
been enabled, battery strength and the amount of
remaining memory (Memory __ % FULL) will be
displayed. If GPS data is being recorded as well, the
meter will display the status of the GPS signal. The meter
will then proceed to the standard reading mode.
IMPORTANT: The GPS unit must be powered up,
have located the satellites and been connected to the meter
before turning the meter on (see “Connecting to GPS
Unit”, p. 8).
Initial Startup
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The computer
Communications Port to
which the cable is
connected can be
identified by using a paper
clip.
1. Disconnect the serial
cable from the meter.
2. To bring up the Port Selection screen, click on the
Com Port Button, select the com port to be tested and
click the Port Test button. Click the Test Port Now
button. If the message “Connection OK” is displayed,
another device (such as a modem) is probably connected
to that port. If the message “No Connection” is displayed,
this port may be the one connected to your serial cable and
you can proceed to the next step.
3. Place a paperclip on the end of the serial pin so that it
touches both the tip of the pin and the metal area between
the two black rings. Again click on the Test Port Now
button. If the message “Connection OK” now appears,
this is the com port connected to your serial cable.
paper clip
or wire
Identifying the
Correct Com Port
NOTE: The meter does not short-circuit the serial pin.
Therefore, when the Test Port Now button is clicked
while the meter is connected, the “No Connection”
message will be displayed.
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Connecting to a
GPS Unit
The data logger function must be enabled using the Field
Scout software in order to record a GPS signal (see
“Meter Settings”, p. 18).
The GPS unit must be plugged into the TCM500 meter
and working when the meter is first turned on. If a GPS
signal is found at startup, the logger will search for a GPS
signal for every reading. If no GPS signal is found when
the meter is first turned on, the meter will not search for
one when taking readings, thereby saving time when
taking readings. In this case the LCD will display the No
GPS Found message.
If the GPS signal is found while taking geo-referenced
readings, the LCD will briefly display the message,
“Reading GPS ..” before displaying the measurement. If
the GPS signal is lost during a series of readings, or if the
specified differential correction is not found, the LCD will
read “Reading GPS .. ERR” before returning to
measurement mode. In this case, the data will be recorded
without latitude and longitude. During subsequent
readings, the meter will again search for a GPS.
GPS Setting
Your GPS unit must be set for NMEA 0183 input/output
messages. If the meter has trouble receiving the GPS
signal, check that the GPS unit has the following settings:
Data bits: 8 Stop bits: 1
Baud rate: 4800 bps Parity: None
Timing: 1 second GGA data string
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Cable Connections
A GPS/DGPS cable (item # 2950CV5) is required to con-
nect the TCM500 meter to a GPS unit. This cable has a 9-
pin male connection and a stereo pin that connects to the
meter’s data port. You will also need a cable that allows
the GPS unit to connect to a 9-pin male serial port. If this
cable doesn’t come standard with your GPS unit, it should
be available from the manufacturer. This cable is gener-
ally used to upload information from a computer to the
GPS unit. These components should be connected as
shown in the figure below.
If you are using the T-handled probe, the y-splitter cable
must be used to connect both the handle and the GPS re-
ceiver to the TCM500 simultaneously. See “T-handle” (p.
10) for more information.
Connecting the TCM500 meter to a GPS unit
GPS computer
interface cable
GPS
Unit
Spectrum
GPS/DGPS
Cable
TCM500
Meter
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T-Handle
The T-handle probe (item 2975H) is
an accessory for the TCM500 that
allows a user to take measurements
from a standing position. When
connected to the meter, the red button
on the handle performs the exact
same function as hitting the READ
button.
Connecting the T-Handle to the
TCM500 meter
The connector of the T-handle has 2
screws that are used to attach the T-
handle to the handle of the TCM500.
The procedure for connecting the
handle is as follows:
1. Loosen the nuts on the screws. Do not remove the nuts.
2. Position the connector over the meter’s handle. Take
care that T-handle is positioned so the red button is facing
forward.
3. Push the nuts through the holes on the handle.
4. Slide the connector sideways so the screws are inserted
in the notches in the handle holes.
5. Tighten the screw to secure the T-handle to the meter
handle.
6. Remove the plastic cap from the data port on the lower
left corner of the meter.
7. Insert the 3.5mm serial plug into the data port.
Note: If you are also connecting the TCM500 to a GPS
receiver, the y-connector included with the T-handle
should be plugged into the data port first. The T-handle is
then connected to one connector and the GPS/DGPS cable
(item 2950CV5) is connected to the other.
T-handle connected
to TCM500.
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Keypad Operation
The ON button turns the meter on and off.
When the meter is turned on, it will dis-
play the battery status for 3 seconds. If
the data logger is enabled, a logger status
screen will appear. The screen will then
display the amount of memory available and the status of
the GPS connection. The meter then goes into standard
reading mode. See below for a sample sequence of meter
power-up screens.
CAUTION: If the meter is inactive for 10 minutes, it will
automatically turn off to conserve power. When the meter
is powered off, either with the ON button or due to inac-
tivity, the AVG and N values are reset to zero (see
“Standard Reading Mode”, p. 14)
ON
BATTERY AT 85%
V7.0 Battery status screen
LOGGER 28% FULL
NO GPS FOUND
LOGGER 35% FULL
GPS=YES DGPS=YES
Logger and GPS status
screens
When the Delete/Clr Avg button is
pressed and immediately released,
the last data point will be and the
running average. Pressing and hold-
ing this button will reset the running
average (AVG) and N-value to zero.
Delete
Clear Avg
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Measurements are taken by pressing the
READ button. The turf color data, in
the currently selected mode (see be-
low), will be displayed on the top line
of the LCD.
The reading is also incorporated into the running average
(AVG) and the sample number (N) is incremented. The
current AVG and N are both displayed on the bottom line
of the LCD. Up to 64 RED/NIR readings (N064) can be
included in the running AVG. If more than 64 readings
are taken before the data series is cleared or the meter is
turned off, the AVG will not be updated. See “Standard
Reading Mode” (p. 15) for more details.
Read
The MODE button selects which of
three data formats will be displayed on
the LCD. The mode can be changed
after a measurement to view measure-
ment values in different formats. The
TCM500 has three display modes; RED/NIR, NDVI, and
Grass Index. See Meter Indexes (p. 20)
NDVI
The equation for NDVI computation is shown on p. 20.
Grass Index
The meter uses the reflectance values to compute a grass
index (see p. 20)
RED/NIR
Displays the % reflectance in the RED (660 nm) and NIR
(850 nm) wavelength bands.
MODE
RED/NIR = 17.1/ 60.5%
N002 Av = 15.1/ 62.3%
NDVI = .462
N022 Av = .501
Grass Index=3.60
N010 Av=4.10
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Adj. Grass Index
From this screen, you can modify the default grass index
to match your own evaluation of the turf. See “Adjusting
the Grass Index”, (p. 21) for details on this procedure.
ADJ. GRASS INDEX
Hit Del to Edit
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Taking Readings
When in standard reading mode, the LCD of the TCM500
will display the turf color data and a running average. The
average value remains in the meter’s short-term memory
until it is deleted or the meter is shut off (see “Keypad
Operation”, p. 11). If the data logger is enabled, the data
is also recorded in the logger’s memory.
Do not take measurements when dew is present or when
turf is wet following irrigation. Since moisture on turf
affects the amount of reflected light from the samples,
meter readings will not be accurate.
Readings will NOT be affected by ambient light (sun
versus clouds) conditions. The TCM 500 has its own
internal light source, allowing measurements to be made
any time.
When measuring “taller” grass, it may be necessary to
press down on the meter/sample such that ambient light is
blocked out. Excessively bright ambient or reflected light
will saturate the light sensors and thereby cause invalid
readings. When the light sensors near the saturation point,
an LCD message of !!ERROR!!, EXCESSIVE LIGHT
will appear.
Meter Display
When in a measurement mode, the first line of the LCD
will be the index reading in the currently selected mode
(RED/NIR, NDVI, Grass) (see MODE button, p. 12).
The second line gives information about the running
average (AVG) and current sample number (N).
As each reading is taken, i.e. each time the trigger is
released, the INDEX reading is incorporated into the
Standard Reading Mode
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running average (AVG) and the sample number (N) is
incremented. The current AVG and N are both displayed
on the bottom line of the LCD.
Only a maximum of 64 INDEX readings (N064) can be
used to generate the running AVG. If more than 64
readings are taken before the short-term memory is
cleared, the AVG will remain at the value it had at
N=64. However, deleting an INDEX reading from short-
term memory (thus causing a new AVG to be calculated)
does not free up memory space for storing an additional
reading. In other words, the average is not calculated if
the READ button has been pressed more than 64 times
without clearing the average.
Valid index readings can be taken beyond the maximum N
value of 64. But N will not continue to increment unless
the entire current data series is cleared, resetting N to zero.
Logging Data
The data logger must be enabled in order to download
data to a PC. In the Field Scout software, clicking a
button entitled Meter Settings will display a screen that
has Enable Meter’s Logging Function as an option. The
box associated with this option must be checked in order
to log and download data. Files downloaded from the
TCM 500 meter are comma-delimited text files and can be
opened in any word processing, spreadsheet, graphing, or
statistical analysis program.
There are six columns in the downloaded text file. If GPS
is used, longitude and latitude are in the first two
columns. Otherwise, these 2 columns are empty. The
sample number N, the %RED, %NIR, and NDVI are in
the remaining columns (see “Data Files”, p. 19).
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Com Port
The black software cable connects
the meter to the computer data port.
Select the Com Port that is assigned
to the computer data port. See
“Identifying the Correct Com
Port” (p. 7) for instructions on how
to determine which port to select.
Meter Type
Select the TCM 500 (NDVI Type)
option from the list of available Field
Scout meters.
Field Scout
Software Toolbar
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Download
To download data from the internal data logger, turn the
meter off and connect the gray serial cable to the RS-232
port beneath the ON button on the meter face plate. Click
the Download button on the main software screen. In the
Save Data As screen (see below), give the file a descrip-
tive name and select the location where it will be saved.
When the file has been saved, the software will give you
the option of immediately viewing the file. The data file
is stored as a comma-delimited text file and may be
viewed in text editor or spreadsheet software.
Clear Memory
The logger continuously adds to its memory until the
logger is manually cleared by the Field Scout software.
Data is not automatically removed from the logger mem-
ory after a download. The Clear Memory button initiates
the clear memory sequence. The software then warns you
that you are about to clear the memory. Once you have
cleared the logger memory, there is no way to retrieve the
logged data from the meter.
Meter Settings
Click this button to configure the meter and data logger.
Refer to “Meter Settings” (p. 18) for more details.
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Meter Settings
The Meter Settings screen in the Field Scout software is
used to configure the meter and data logger for your spe-
cific application. It is accessed by clicking the Meter Set-
tings button or selecting Edit Logger’s Name and Set-
tings from the Logger menu. The fields are described
below.
Meter Name: The name given the meter will be the title
on the first line of the downloaded text file.
Logger Settings: The data logger is enabled and disabled
by checking the first box. If the data logger is enabled, it
will search for a GPS signal when the meter is turned on.
If a signal is found, position data will be stored along with
the soil moisture data. If no GPS signal is available when
the logger is turned on, the logger will no longer look for
one when measuring and recording soil moisture data. If
the second box is checked, the logger will store the GPS
value only if it has been differentially corrected. If the
differential correction is not found, only the soil moisture
value will be stored in the data file. A time-zone correc-
tion should be entered in the third box. Appendix 2 lists
time zone corrections for several cities.
The Meter Settings screen in the Field Scout software is
used to configure the meter and data logger for your spe-
cific application. It is accessed by clicking the Meter Set-
tings button or selecting Edit Logger’s Name and Set-
tings from the Logger menu. The fields are described
below.
Meter Name: The name given the meter will be the title
on the first line of the downloaded text file.
Logger Settings: The data logger is enabled and disabled
by checking the first box. If the data logger is enabled, it
will search for a GPS signal when the meter is turned on.
If a signal is found, position data will be stored along with
the soil moisture data. If no GPS signal is available when
the logger is turned on, the logger will no longer look for
one when measuring and recording soil moisture data. If
the second box is checked, the logger will store the GPS
value only if it has been differentially corrected. If the
differential correction is not found, only the turf color data
will be stored in the data file. A time-zone correction
should be entered in the third box. Appendix 1 lists time
zone corrections for several cities.
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The data is stored in comma-delimited text files. These
files can be opened with text-editing software (e.g. Note-
pad) or spreadsheet software (e.g. Excel).
The first two lines of the data file give the logger’s name
and serial number. The third line indicates that latitude
and longitude are referenced to the 1984 World Geodetic
Survey datum. The fourth line shows the column head-
ings for the rest of the data file.
Logging sessions are started and completed by turning the
meter on and off. The start of a logging session is indi-
cated by the data line “Logger Started.” If a GPS signal
was found at the start of a logger session, a time stamp is
included on the “Logger Started” line.
The data file is separated into 6 fields: Latitude and Lon-
gitude (blank if a GPS unit was not connected), sample
number, Red reflectance, Near Infrared reflectance, and
NDVI. The Grass Index is not saved in the data file.
Sample data showing results of data collected with and
without GPS activated. Note: GPS signal not found when
recording data in lines 10 through 15.
Data Files
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Meter Indexes
The LCD of the TCM500 NDVI meter displays
measurements in one of three modes (see MODE button
p. 12). The modes are described below:
1.) Normalized Difference Vegetative Index (NDVI)
NDVI is defined as:
NIR - Red
NDVI = ----------------
NIR + Red
Where:
NDVI = Normalized Difference Vegetation Index
NIR = Reflectance in the band of 850 + 5 nm
Red = Reflectance in the band of 660 + 5 nm
2.) Grass Index (Factory Default)
The Grass Index has a scale of 1 to 9 and approximates
the rating a visual observer would assign to the turf grass.
This provides a more objective value for this, generally,
very subjective parameter. The Grass Index is calculated
as follows:
Grass Index = (NDVI X 6.6) + 2.26
Note: If the index has been manually adjusted (p. 21), the
offset value is no longer 2.26. Rather, a new offset is
calculated so the index value shown on the LCD matches
the user’s evaluation of the turf’s color.
3.) Reflectance Values
The percent of incident light of each wavelength band that
is reflected back to the optical sensor in the meter. These
same reflectance values are used to calculate NDVI and
the Grass Index.
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