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Tying Files To The Outside World |
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Compass can process files as stand-alone surveys that aren't unconnected to anything out side of themselves. However, it is often useful to connect survey files together. For example, you might have several caves in an area and you might want to see how they relate to each other. It is also useful to tie surveys to the outside world. The is allows you export them to GIS programs, find surface locations that are nearest to a survey station or display the cave in programs like Google Earth to see how cave passage relate to survey features.
Compass, has three options for tying survey files together. 1) You can Link them together. 2) You can tie them to a local coordinate system. 3). You can tie them to a world coordinate system like Longitude/Latitude and UTM.
1. Links. Links allow you to tie caves together that have duplicate station names. For example, you might have two caves that both have an A-survey. That means that both files are likely to have stations like A1, A2, A3, etc. If you simply combine the files in the same project, the A1 in one file, will interfere the A1 in the other file. Links solve the problem by isolating survey files from each other. Click here for more information on Links.
2. Local Coordinates Systems. Before GPS receivers were commonly available, surveyors often tied caves in an areas to a local landmark. For example, the caves of Huautla system in Mexico were originally tied to the corner of a church. The local landmark becomes the base location for the area and it has a coordinate of zero east, zero north and zero vertical (0,0,0). All other locations in the system are relative to that point and any time Compass display a coordinate or elevation, it will be relative to the landmark.
To use a Local Coordinate system, you create Fixed Stations whose coordinates are the relative to the base location. Since you are not using world coordinates, you only enter East, North and Vertical values; you don't enter UTM, Zones or Longitude and Latitude. Click here for more information about Fixed Stations. Click here for information about entering and editing fixed stations.
3. World Coordinates. Compass allows you to specify Fixed Stations in geographic coordinates such as Longitude/Latitude or UTM. Basically, this ties the cave to a place on the globe and all the coordinates that appear in Compass are relative to world coordinates. This is useful because it allows you to export cave data to GIS programs programs such as ArcGIS or OpenGIS. It also allows you to export your data to Google Earth and display the cave passages on Google Earth aerial photos.
To use World Coordinates, you create Fixed Stations whose coordinates are either UTM or Longitude/Latitude. . Click here for more information about Fixed Stations. Click here for information about entering and editing fixed stations.
For more detailed information, follow these links:
Entering and Editing Links and Fixed Stations Viewing Geo-referenced Coordinates Mixed Linked and Unlinked Files Closing Loops Across Separate Data Files Manual Linking Multi-File Surveys.
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