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Once the
p roject
configuration has been completed, you are ready to
perform the actual
survey by walking the site with a portable PC that runs TamoGraph
(unless you perform a predictive
survey, where no
on-site data collection is necessary). To
facilitate the data collection process, TamoGraph offers three
survey modes that can be selected by pressing the corresponding
buttons on the tool bar: Continuous (the
left button on the illustration), Point-by-Point (the
middle button on the illustration), and GPS (the
right button on the illustration) for GPS-assisted outdoor
surveys.
In the
default continuous
mode, after you mark
your initial location on the map by clicking on it, the application
scanner continuously scans the air by sweeping through the Wi-Fi
channels. When you mark the next location on the map, the data that
has been collected between the two clicks on the map is spread
evenly along the path between the two data points. This means that
your path should consist of straight lines and that you should walk
steadily, clicking on the map every time you change
direction.
In
the point-by-point
mode, TamoGraph
collects data only when you click on the map. In that mode, you
should stay where you are after marking your location on the map,
until the scanner completes the cycle. Then the scanner stops,
until you mark your next location, where the scanner makes another
full cycle. This means that your path can have any shape, but less
data will be collected, as compared to the continuous mode, and a
smaller area will be covered.
In
the GPS
mode, the data
collection process is similar to the one
in continuous
mode, but the
location is automatically determined by the GPS receiver connected
to the computer. Continuous and Point-by-Point surveys
can be conducted both indoors and
outdoors; GPS surveys
can be conducted outdoors only, as GPS receivers cannot receive
location data when indoors.
Before you
begin, spend some time thinking through your walkabout path. Decide
which areas you need to survey and how you are going to do that.
Remember that it is quite all right to mix the three data
collection modes—that is, you can survey some areas where walking
steadily in a straight line is not a problem in continuous mode;
you can then survey other areas in point-by-point mode, and then
survey the area outside the building in GPS mode. You can also stop
the survey at any moment and continue after a break, as you can
select several survey segments for data analysis. Once you have
thought through your walkabout path, begin the actual
survey.
TamoGraph allows
you to perform two types of surveys: active and passive (or
both at the same time). Every time you start data collection, you
will be prompted to select the type of survey, as shown
below.
It
is extremely important to understand the difference between the two
survey types, as
they focus on different WLAN characteristics. Please refer to Understanding Survey Types: Passive, Active, and
Predictive for more
information. When performing an active survey, an additional
configuration dialog is displayed before you can start data
collection. This dialog is explained in the
Active
Survey Configuration chapter. Additionally, when a compatible
spectrum analysis
device is connected
to the computer, you will be able to collect spectrum data either
in parallel with a passive survey (the first dialog option will be
titled Passive Survey +
Spectrum Survey) or in
spectrum-only mode (another option titled Spectrum Survey
will be added to the
dialog).
Continuous Mode: To start
data collection, click on the Start button
(illustrated on the   left)
and then mark your initial location on the map by clicking on the
corresponding spot. Walk along the planned path at a steady pace in
a straight line. You should walk a bit slower than you normally do.
Every time you reach the end of the straight line on your path
(i.e., every time you need to change direction), click on the map
again to mark your current location. Data collection stops when you
click on the Stop button
(illustrated on the right.)
Point-by-Point Mode: To
start data collection, click on the Start button.
Mark your location on the map by clicking on the corresponding
spot. TamoGraph will collect data by scanning the channels twice
and display a notification at the bottom of the window when all the
data has been collected. Proceed to the next point on your path and
mark your location again. Repeat until you have surveyed all the
planned points. Data collection stops when you click on
the Stop button.
GPS Mode: To
start data collection, turn on your GPS receiver, connect it to
your computer, and then click on the Start button.
Your current location will be displayed on the map with a circle.
Make sure that the displayed location matches your actual location.
If it does not, you made a mistake while calibrating the map with
reference points, and you need to re-calibrate the map. Walk or
drive slowly along the  planned path.
The slower you drive, the more Wi-Fi data will be collected, and
the more accurate the data analysis will be. GPS surveys can be
conducted outdoors only, in open areas where a GPS receiver can see
many satellites. Location data accuracy is directly related to the
number of satellites in view. As you move along the path, location
data accuracy is indicated on the application status bar, as shown
on the illustration. If location data accuracy becomes poor, you
may want to stop the survey until more satellites become visible to
the receiver (you can click on the data accuracy indicator to
display the GPS receiver configuration dialog that displays
accuracy level and visible satellites). Data collection stops
when you click on the Stop button.
When
you are through with the survey, you can proceed to the data
analysis of a passive and/or active survey.
However, before you do, it is recommended that you read the next
three chapters, especially if you are new to Wi-Fi site surveys.
They provide important information about the available types of
surveys, their purpose, as well as some valuable tips and tricks to
make your site surveying more efficient.
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