SURVEYING
FROM AN UNKNOWN POINT
FROM AN UNKNOWN POINT
WITH
LEICA TOTAL STATION
The total station can be used to survey in locations where you
do not know the value of the point upon witch it is setup upon, this is known
as Free Station Surveying. This survey technique is often used when you have
two points with known established coordinate values but are not in an ideal
place to perform your survey from, or at times where you wish to progress
further into an unknown survey region.
do not know the value of the point upon witch it is setup upon, this is known
as Free Station Surveying. This survey technique is often used when you have
two points with known established coordinate values but are not in an ideal
place to perform your survey from, or at times where you wish to progress
further into an unknown survey region.
A good example for using this technique would be if you needed
to measure points under a dense forest canopy where your GPS could not provide
high precision point values. In a case like this you would use the GPS unit to
establish known values around the perimeter of the tree stands and then use
them as back-sights so that you can setup your total station in under the
forest canopy.
to measure points under a dense forest canopy where your GPS could not provide
high precision point values. In a case like this you would use the GPS unit to
establish known values around the perimeter of the tree stands and then use
them as back-sights so that you can setup your total station in under the
forest canopy.
You would then be able to establish the value of this unknown
point and then continue collecting other unknown points as well. Accurate
results from this style of surveying rely on careful planning and the use of
good geometry when setting up your known point.
point and then continue collecting other unknown points as well. Accurate
results from this style of surveying rely on careful planning and the use of
good geometry when setting up your known point.
Set up is similar in many
ways to the set up technique explained earlier when surveying with the total
station setup over a known station. Therefore we will assume that you can
follow the steps outlined above in earlier sections for instructions on setting
up the total station, leveling the unit and measuring the HI.
– Create the measure job, data job and select codelist as outlined previously (all the
steps are the same).
steps are the same).
– Once the
above steps have been taken return back to the main menu and press the PROG key from the bottom row of the key
pad.
above steps have been taken return back to the main menu and press the PROG key from the bottom row of the key
pad.
– Next
select Free Station from the program Selection menu by
pressing 1 on the key pad.
select Free Station from the program Selection menu by
pressing 1 on the key pad.
The station
ID is a uniquely identified for the point that you are occupying. It is
good practice to use the point id values of the two known points that you will
be measuring as this identifier. Something like pt1 or pt2 can also be
used.
ID is a uniquely identified for the point that you are occupying. It is
good practice to use the point id values of the two known points that you will
be measuring as this identifier. Something like pt1 or pt2 can also be
used.
– Enter the instrument
height (HI) of the total station. Press CONT by using the F1 key.
Now you will
be on the Target Point screen.
be on the Target Point screen.
– Enter the
ID of the first known point you wish to use. Enter height of reflector pole
with the prism above the unknown point. Aim the total station towards the
reflector.
ID of the first known point you wish to use. Enter height of reflector pole
with the prism above the unknown point. Aim the total station towards the
reflector.
Then shoot
the laser at the reflector with SEARCH by hitting the F1 key.
the laser at the reflector with SEARCH by hitting the F1 key.
On the next
screen press F2 to use the DIST function. Keep pressing the using the DIST function until the number you see is
resolved to within 5mm of the last two DIST measurements. After you are satisfied
with the value that was resolved from the measurement process then Press F4 CONT.
screen press F2 to use the DIST function. Keep pressing the using the DIST function until the number you see is
resolved to within 5mm of the last two DIST measurements. After you are satisfied
with the value that was resolved from the measurement process then Press F4 CONT.
Repeat these
steps for the second known point.
steps for the second known point.
Once these
two points have been shot use the F6 button to access the CALC function. This
will do the math for the total station to figure out where it is set up upon.
The total station will know spatially where it is located so that it can
measure and calculate more unknown points within the survey area.
two points have been shot use the F6 button to access the CALC function. This
will do the math for the total station to figure out where it is set up upon.
The total station will know spatially where it is located so that it can
measure and calculate more unknown points within the survey area.
Note: You may result with an error screen
telling you the error calculation is too large. If this occurs you must try to
resolve this by shooting to the two known points again to obtain better, more
accurate data. What has occurred is that the place where you told the
Total station that the two points are not matching up wit the math it does to
confirm that and establish it own position.
telling you the error calculation is too large. If this occurs you must try to
resolve this by shooting to the two known points again to obtain better, more
accurate data. What has occurred is that the place where you told the
Total station that the two points are not matching up wit the math it does to
confirm that and establish it own position.
If everything is fine you will arrive at a screen that will give
you and option on the bottom left screen above the F1 key SET. Press F1 to establish the Total Stations
position. This brings you back to the main menu.
you and option on the bottom left screen above the F1 key SET. Press F1 to establish the Total Stations
position. This brings you back to the main menu.
You can now use the MEAS function to begin your survey as per
the instruction in setting up over a known point explained above.
the instruction in setting up over a known point explained above.
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