Open/Create Location Database

Use the Gravity > Locations > Open/Create Location Database menu option (GRXYEDB GX) to open or create a location database that contains location and elevation information for the current project.

Open/Create a Location Database dialog options

Location database

The name of the location database. If the database does not exist, it will be created with channels of "Station", "Longitude", "Latitude", "X", "Y" and "Elevation". You will also have the option to load existing location data from another database or a text file.

If the database does not exist, you will be asked to confirm that you want a new database to be created and you will have the opportunity to import the data from another source into the new database. See GRLDXYE GX for more information on importing location data.

Application Notes

The surveying of gravity station locations is often carried out separately from the gravity survey. This GX will allow you to create a location database that contains the gravity survey locations alone. The locations can be merged with the raw survey data as part of the drift correction, or they can be merged into any database that contains a "Station" channel. The location database can also be used to create maps to show the planned locations of gravity stations before or during the collection of gravity readings.

Location information can also be entered directly into the survey databases, or imported from a RAW gravity data file in which case you will not need a location database.

The location database will contain the following channels:

"Station"	A unique station number that is used to look-up locations during the drift correction or when you merge location data using the "Merge with survey data…" (GRMGXYE GX).
"Line"	The "Line" channel will only be present if there is "Line" data in the imported location file. If "Line" is present, station locations are based on a unique Line and Station. This may be the case if a gravity survey is conducted on a local line/station oriented survey grid.
"Longitude" "Latitude"	The geographic location of the station. If only a local grid "X" or "Y" is provided, these values will appear as dummies. The "X,Y -> Longitude, Latitude…" (GRLL2XY GX) can be used to calculate longitudes and latitudes from local X,Y coordinates.
"X" "Y"	The local map X,Y coordinate of the station. The X,Y coordinates may also be in a known map projection. If only a longitude, latitude locations are provided, these values will be dummied. The "Longitude, Latitude -> X,Y…" (GRXY2LL GX) can be used to calculate X,Y coordinates from Longitude, Latitude coordinates.
"Elevation"	The station elevations.

The location database name is stored in the "GRAVRED.LOCATION_DATABASE" parameter (see GRPARM GX).

Distance Units

Distance units are assumed to be degrees for geographic longitude, latitude and metres for "X", "Y" and "Elevation". The distance units can be changed when data is converted between X,Y and geographic coordinates, or the units can be set by editing the channel attributes and specifying the unit abbreviation (click once on a channel name, then right click and select Edit).