Lat/Long to Transverse Mercator
Several different coordinate systems are used in surveying and it is often necessary to convert between them. This function transforms string files from easting, northing and transverse mercator zone to latitude and longitude.
To run this function: Choose File tools > Transformations > Lat/Long to transverse mercator, or...
Define the Input Files
Location, ID Range
Enter the location and range of string files to be converted.
Define the Output Files
Location
A set of string files will be created, each one corresponding to a transformed input string file.
Define Geodetic Coordinate System
TM Map, Datum, Spheroid
There are several different methods to enter the parameters of the transformations to be computed. In the etc directory the file datums.ssi contains the parameters for several different transverse mercator projections and these parameters can simply be selected by clicking on the browser of the TM map field. For globally used TM projections such as UTM, the spheroid to be used must also be selected from the Spheroid field, otherwise the Datum and Spheroid fields will automatically be filled.
Selecting a TM map projection fills in the False Easting, False Northing, Central Scale Factor, Zone Width and Zone 1 CM fields.
TM parameters can be entered manually by selecting TM from the TM Map field, the spheroid from the Spheroid field and filling in the appropriate parameters for the False Easting, False Northing, Central Scale Factor, Zone Width and Zone 1 CM fields.
Define String File Format
Long/Lat Units
Longitude and latitude can be expressed in several different representations:
dms (deg,min,sec) - Degrees, minutes and seconds format (e.g. 5045'23.99")
degrees - Decimal degrees (e.g. 50.7567)
radians - Radians (e.g. 0.88587090)
degrees, minutes - Degrees and minutes format (e.g. 5045.3998')
Select the appropriate representation found in the string files.
North Positive, East Positive
If latitude is measured as positive north then North Positive should be set to "Y", otherwise "N" should be selected. Similarly longitude may be measured in the east direction or the west direction. If longitude is measured as positive east then set the East Positive field to "Y", otherwise "N" should be selected.
Input Fields
Depending on the representation of latitude and longitude used a different number of fields will be needed to specify a geodetic position. For example, decimal degree numbers require one field; degree, minute and second numbers require three fields. The fields used in each point record in the string file to specify the latitude and longitude must be entered.
Output Fields
A transverse mercator projection is specified by zone, easting and northing. Often all coordinates are in the same zone and this may not be wanted in the output files. In this case, enter a blank value in the TM Zone field. Otherwise select the desired fields to output the zone, northing and easting.