Entering Fixed Stations, Plus Step-By-Step Instructions

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In COMPASS, Fixed Stations can only be entered at the "Project" level. The advantage of this is that since COMPASS can have more than one Project for the same data, you can have more than one set of geographic reference points for a particular cave. For example, you could have one Project where the cave is tied to a local reference and another where it is tied to UTM.


The Linked/ Fixed Station Page. An image of the Linked/Fixed Station page appears below:




The page is divided into several sections. Here is a detailed description of each section:


1. Fixed/Link Grid. This grid allows you to enter stations and the East, North and Vertical position of the stations. You just type the values you want to enter into the cells. You can insert as many rows as you want, anywhere you want, but the program ignores everything after the first blank row. You can use the Insert Button to insert a blank row between existing rows. You can use the Delete Button delete the highlighted row. The values can be in feet or meters.


2 UTM Coordinate Box. The values you enter can be tied to any coordinate system you like. If you want to use UTM or Longitude/Latitude coordinates, you should enable the Use UTM option. Once it is enabled, you can enter a Default UTM Zone for the project. This is UTM Zone that is used for all fixed survey points in the projects. If one or more fixed points fall outside the Default Zone, you can use the Zone Crossing UTM button to handle these coordinates. Finally, you can use the Geo-Calculator to enter UTM or Longitude/Latitude coordinates.


3. Convergence Box. One of the issues with UTM coordinates is that north does not always point to the North Pole or  True North. This is because the UTM Grid is flat whereas the earth spherical. The UTM Convergence option allows you to correct for this problem. You can enter your own angle using your own calculations or use the Geo-Calculator to do if for you.


4. Units. The value you enter can be in either feet or meters. The Units box indicates which units you are using. If the Convert Units checkbox enabled, changing the Units setting will convert the all the entries in the Grid to the newly selected units. If it is disabled, the you can change the units and the numbers in the Grid will stay the same values.


Step-By-Step Instructions


1. Project Manager. Since Fixed Stations are created at the project level, you must go to the Project Manager to enter a Fixed Station. You cannot do this operation from the Editor.


2. Creating A Project. The Project Manager can work with either individual ".DAT" survey files or ".MAK" project files. Since the fixed stations are entered at the project level, you must have a Project File before you can enter a Fixed Station. If you don't have a Project File, go the "Project Creation Wizard" on the "File" menu of the Project Manager. Just follow the instructions. If you already have a Project, you can use it.


3. Opening The Project. Once you have Project File, open it with the Project Manager. Remember that this must be a file with the "MAK" extension like LECH.MAK. You cannot use "DAT" file to create a link. Once you have opened the Project File, click on the "Expand Tree" button on the tool bar at the top of the screen. This will expand the "Survey Tree" to show all the "Nodes."


4. Selecting Survey File. You now need to select the survey file that has the station or stations you want to use as a Fixed Station. Just click on and highlight the survey file in the "Tree." Now click on the "Edit Node" button at the top of the screen. This will display the Node Editing dialog box. Select the "Links Tab" at the bottom of the page. This will take you to the Links Editor.


5. Entering Links. The Links Editor displays a grid that allows you to enter the station name and the North, East and Vertical coordinates of the station. Enter the coordinates of the station in the cells to the right of the station name. The units can be feet or meters as selected by the check boxes below. As an example:


A1  10.1  20.2   30.3


This illustrates a fixed station. The station A1 is fixed to the location 10.1 east, 20.2 north and 30.3 vertical from the fixed reference point.


The East, North and Vertical coordinates can be in either feet or meters. The coordinates can be relative to a local coordinate system or a worldwide geographic reference system. COMPASS uses UTM as its internal reference system; however, it can convert to and from longitude and latitude. To use geographic referenced coordinates, enable the "Use UTM" checkbox. If you are using UTM, be sure to set a "Zone" number. Only one zone is allowed for each cave file, but you can have different files in different zones. You can enter up to 500 Links for each survey file.


If you want to enter the data in Longitude and Latitude, first highlight the row in the grid for the station you want to set. Then, click on the "Geographic Calculator" button. The program will then display a dialog box that will allow you to convert back and forth between Longitude and Latitude and UTM. At the bottom of the box will be the UTM coordinates in meters. (Note: UTM is always displayed in meters on maps.) If you enter Longituted and Latitude coordinates, they will automatically be converted to UTM. Likewise, if you enter UTM coordinates, they will automatically be converted to Longitude and Latitude.This way, you can enter longitude and latitude values. You can also use the dialog to verify your UTM coordinates by converting them to longitude and latitude and then checking the map.


6. Zone Crossing Links. If you have more than one fixed station that crosses from one UTM Zone to another, Compass has special options for dealing with zone crossing. Click here for more information.


7. Convergence. Cave plots are normally aligned to True North or Magnetic North. (This depends upon whether you have used Declinations to convert Magnetic North to True North.) Because of the fact that the square, UTM grid is superimposed on a spherical earth, the UTM grid may not be aligned with true north. The Convergence option allows you rotate the plot so it aligned with the UTM Grid. This is done by subtracting the Convergence Angle from the Azimuth of each shot.


To use the Convergence Option, enable the "Use Convergence" checkbox and enter a value into the "Convergence" box. Normally, you would get the Convergence value by pressing the Geographic Calculator button, which will allow you find the Convergence value based on the location on the earth. Normally, the Convergence value is limited to a range of minus three to plus three. However, you can also enter other numbers not based on Convergence to add a rotation to the cave file. With "Use Convergence" checkbox enabled, the cave will be processed with this section rotated to match the local UTM grid.


Important: Since the convergence angle rotates the cave from true to UTM grid north, you must correctly set the declination before using convergence. This will assure that all the shots align to true north before they are aligned to the grid.


Since Convergence is set as a part of the Fixed Stations used with each file, the Convergence takes effect at the point that the file is processed. Once the Convergence is set, it remains in effect until it is modified. If it is not modified, it remains in effect for all remaining files.