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Remote Distance Measurement

The faulty cable on the Electronic Measurement Device (ie. Total Station) that we had at the 2008 Olympic Trials got me thinking. If the primary electronic measurement system fails and we do not have a backup system, is there some way to continue to measure the throws electronically?

I did some investigating and found it is possible to use an Electronic Measurement Device (ie. Total Station) to measure a throw without using a LaserLynx Palm or iPaq or any any handheld. The EMD was designed for surveyors and measuring between two points is pretty basic. You'll still need to subtract the radius of the circle from the total station calculation, but that can be performed on a simple calculator.

I tested the procedure on my Pentax 325N Electronic Total Station. There are several special functions built into the Pentax 325N Electronic Total Station that allow the surveyor to handle a variety of measurement situations. One of the special functions is called Remote Distance Measurement (RDM).

The user manual states, with RDM measurement, the horizontal distance, the slope distance, difference in height and the percentage of slopte between the reference point and the observation point are measured. The distance between one observation point and another observation point is measured as well.

For the USATF Official measuring long throws, the base point is the center the the throwing circle. The various observation points are the landing marks of the javelin, discuss, hammer or shot. The distance of the throw is the horizontal distance as measured and displayed on the Pentax 325N Electronic Total Station less the radius of the throwing circle (ie. 8 meters for the javelin throw, 1.25 meters for the discus, and 1.06 meters for the hammer, weight and shot.)

Here are steps for using the RDM special function on using the Pentax 325N Electronic Total Station.

Accessing the RDM Special Function

  1. Press the [POWER-SUPPLY] key to turn on the Total Station.
  2. Press the [Laser] or [ESC] button. That will take you to the MODE A screen. The display above the numbered function buttons will change to
    MEAS    TARGET    0 SET    DISP    MODE
  3. Press the MODE [F5] button. That will take you to MODE B. The display above the numbered function buttons will change to
    S.FUNC   ANG SET   HOLD    COOR    MODE
  4. Press the S.FUNC [F1] button. That will take you to the Special Function Menu.
    1.DATA STORAGE
    2.COORDINATES
    3.COORD.STAKEOUT
    4.OFSETT SHOTS
    5.RESECTION
    6.RDM
    7.REM
    8.DIST STAKOUT
    9.MEMORY MANAGER
  5. Press the [UP-ARROW] or [DOWN-ARROW] button until you see 6. RDM.
  6. Press the [OK] button.

Operating the RDM special function

  1. The center of the throwing circle is the Reference point. Have an official hold the prism pole in the center of the throwing circle. (This process is identical setting the Controls in the LaserLynx software.)
  2. The Total Station allows you to enter the prism height. We do not need the elevations so do not enter a value. When prompted with INPUT PRIZM H, press the [ENT] button. Sight the reference point. Then press the [MEAS] button. The Total Station will display the distance to the center of the throwing circle.
  3. The target point is the point where the implement landed. An official will place the prism pole at the target point. As before, the Total Station allows you to enter the prism height. When prompted with INPUT PRIZM H, press the [ENT] button. Then, sight the target point and press the [MEAS] button. The Total Station will display the distance between the center of the throwing circle (reference point) and the prism marker in the field (P1).
  4. Use a calculator to subtract the circle radius from value on the display to obtain the distance the implement was throw. On the next throw, sight the prism pole at the new target and press the [ENT] button. The distance between the center of the throwing circle (reference point) and the prism marker in the field (P1) will display on the screen. This The Total Station has the ability to display the straight line distance between the last two throws (P1 and P2). Press the [DIST] button to display the straight line distance beteen the last two throws (P-P). For our task and a measurement official, that information is unnecessary. Press the [DIST] button again to display the distance between the center of the throwing circle and the prism marker in the field.

Are you ready to give it a try? You will notice, after pressing the [MEAS] button, the horizontal distance is displayed instantly. This is considerable faster than transmitting the raw data from the total station to a handheld and calculating the distance in the handheld. If you have a helper to run the calculator, you may be able to measure and display the measurement as fast or faster than using a handheld with the total station.

When I get a moment, I'll add instructions on how to do RDM measurements with the Pentax PCS-200 Series total station, used with the High School LaserLynx.

Hope this helps. -- Justin (20090518)

Part II (needs to be checked for typos)

The Pentax PCS-200 Series total station, used with the High School
LaserLynx.  also has the ability to perform remote distance
measurents. I have not tried to run the RDM on that total station.
Here are steps for using the RDM special function on using the Pentax
PCS-200 Series Total Station.

Accessing the RDM Special Function
----------------------------------
1.  Press the [MODE] button, located on the far right to select the
mode.

2.  Press the [S. FUNC] button, located on the far left to select a
special function.

A list of special functions will display.


STAKE OUT
LOT STAKEING
OFFSET STA
R.E.M.
R.D.M
COORD MEAS
RESEC MEAS
TRAV NEAS
COORD STAKE

3.  Use the [UP-ARROW] and [DOWN-ARROW] buttons to navigate through
the list.

4.  Select R.D.M. to enter the remote distance mode, and press the
[OK] button.



Operating the RDM special function
----------------------------------
With the remote distance measurement function, the remote distances
(horizontal distance, slope distance, height differential, and
percentage grade) between a base point P1 and a target point Px, as
well as a target point Px and another target point Px, are measured.

The total station allows you to select from two measurement options,
[P - P] or [BP-P-P]. With the [P - P] option, you measure the remote
distance from a base point to a target point. With the [BP-P-P] option
selected, you can measure the remote distances from a base point to a
target point and from one target point to another.

We want to select the [P - P] measurement option.

Use the [UP-ARROW] and [DOWN-ARROW] buttons to select the [P - P]
measurement option.

The base point (P1), is the center of the throwing circle.  Have an
official hold the prism pole in the center of the throwing circle.
(This process is identical setting the Controls in the LaserLynx
software.)

Sight the base point and then press the [OK] button.

The target point (P2) is the point where the implement landed. An
official will place the prism pole at the target point.

Sight the target point (P2) and then press the [OK] button.

The display will show the slope distance to P2 and the vertical angle.
The dipaly will also show the height differential between the base
point and P2 and the horizontal distance. We are only interested in
the horizontal distance.

Use a calculator to subtract the circle radius from the horizontal
distance to obtain the distance the implement was throw.

On the next throw, sight the prism pole at the new target and press
the [OK] button. The distance between the center of the throwing
circle (base point, P1) and the prism marker in the field (Px) will
display on the screen. Each time the target is changes, the remote
distances fro teh base point (P1) to the new target point (Px) are
displayed.

To change the base point, use the [S. FUNC] button to go back to step
2 of the remote distance function, and repeat the procedure starting
from step 3, "Sight the base point".

Pressing the [S. FUNC] button during the measurement returns to step 2
of the remote distance measurement function. Pressing the [S. FUNC]
button once more at this point exits the special functions mode and
returns to the normal measurement mode.

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