Lesson Note On How to Carry Out Surveying from a Known Point With Leica Total Station

How to Carry Out Surveying from a Known Point With 

Leica Total Station

When the total station is set up and level over the known point it will require another known point to help calculate the coordinate reference system that the unknown measurements will be measured with. That is to say that the total station will be able to know the angular relation between the easting, northing and elevation of itself and the Easting northing and elevation of the second known point (often referred to as the back sight). Then all of the angles and distances measurements calculated and computed with the laser will be translated into the same east, northing and elevation coordinate space as well.

Create a Measure Job File

From the main menu, select Meas job management by pressing the number 1 on the keypad (from the Main Menu).  The measure job created will be the file that your measured points in your survey will be recorded.

Next press F2 to open the Create new job menu.

Leave all settings at default and enter a new job name by using the letters on the keypad.

The F6 key (NUM) will switch the key pad between numbers and letters.  Note it may take some practice to get used to this switching back and forth.

After the new file name has been entered press F1 to continue.

Next ensure that the job file that you have just created is highlighted and select CONT again by selecting F1 from the keypad.

Create a Data Job File

The data job is where the known or fixed points are stored (the Data job file can be the same as the measure job file but often it is good survey practise to keep these two files separate).

Steps followed for creating a data job file are very similar to those mentioned above for creating a measure job.

From the main menu, select data job management by pressing the number 2 on the keypad.

Next press F2 to open the Create new job menu (and provide a file name like you did above) or select an existing data job file if one exists. Then press F1 to continue.

If it is a new data job file then you will need to input values for the known points.

Select the FNC key from the bottom grey keypad.

Select menu item 5 Data view and Edit

On the next screen select Input from the function key options by pressing the F3 key.

Enter the name of the point id of the known point you wish to create.

Enter the known Easting, Northing and Elevation values for this point.

Press REC to accept the value of the point id

Repeat the steps to enter all the known points that you wish to use in your survey and then use the ESC key until you reach the main menu again.

Select your Codelist

From the main menu, select codelist management by pressing the number 3 on the keypad.

Select the name of the code list you created earlier with the Leica Survey Office software and uploaded to the memory card. Then press F1 to continue.

Record Backsight Locations

From the Main Menu select Setup from the bottom of the screen by pressing F5.

In the Job settings menu you should see the name of your measure job, data job, and code list. If either looks incorrect than go back and select them again using the instructions from the start of this manual.

Select QSET (quickset) from the bottom of the menu using F4.

For the Station Id enter the point id of the known point for the surveying monument that you have the total station set up upon.

Next enter the Backs. Id to select the backsight point id

Enter the instrument height of the total station that you recorded previously in the initial setup.

Enter the base height of the reflector poles used to collect the various points during the survey.  The number to enter here will be the value found above the grasp of the reflector pole. A height of 2 meters is common height for reflector poles in most surveys but sometimes there is a need to use different height values.

Aim the total station instrument towards the survey prism with the and press F2 on the key pad which selects DIST. Ensure that the range pole is vertical and plumb by centering the bubble on the pole. This will allow the Total Station to compute the delta of what you told it where it was and where it is based on the reading of shooting the pole.

Take note of the delta horizontal distance on the screen. Anything under 2cm is considered an acceptable value. Once accuracy under 2cm is achieved hit CONT by pressing F4 on the key pad.  The unit will now know spatially where it is located and surveying of the unknown points can commence.

The screen should now have an option MEAS appear in the lower right corner of the screen, this is an indication that you can now shoot to any unknown point with the reflector. 

 Press the F6 function key to enter into the measure and Record menu. Here you can point and aim at the reflector, enter the point Id value and then press the F3 function key to record the coordinate values of that point. The total station will increment the point ids taken automatically, or you can change the values manually each time.

Tip: Remember to adjust the height of reflector on this screen if the height of the reflector unit is adjusted during the survey.

To finishing surveying simply press ESC until the screen is back to the main menu. Press both the ON button and the left arrow button at the same time to shut down the unit.

Tip: How to adjust the view of the Total Station

Use the “sight” on the total station to roughly point the Total station at the reflector.  Then use the knobs to fine tune the view at the reflector target.  Use the focus on the lens to ensure a clear and focused view of the target and that the cross hairs are centered on the center of the target. 

HOW TO SURVEYING FROM AN UNKNOWN POINT WITH LEICA TOTAL STATION

SURVEYING 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.

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.

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.

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).

– 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.

– Next 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.

– 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.

– 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.

Then shoot 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.

Repeat these 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.

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.

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 can now use the MEAS function to begin your survey as per the instruction in setting up over a known point explained above.