Coordinate Transformations

The coordinate transformation tools allow you to wotk with geographic and rectangular coordinates in the same survey based on a Coordinate Reference System (CRS). You can enter a geographic coordinates for a point and TPC will compute it's equivalent rectangular coordinates or visa versa.

TPC's coordinate transformation tools allow you to work with other geospatial technologies like GPS and GIS. You should have at least a basic understanding of spatial reference systems and how they relate to the rectangular coordinates used in surveying and mapping.

Coordinate Reference System

Each survey has a Coordinate Reference System (CRS) which determines the relationship between geographic coordinates (latitude and longitude) and rectangular coordinates (X and Y). The CRS uses an ellipsoid (mathematical representation of the earth), a horizontal datum (to reference geodetic to rectangular coordinates) and a map projection (to convert the earth's sherical surface to a flat surface).

Terminology

Grid Coordinate - any X,Y coordinate value based on a rectangular coordinate system
Coordinate Transformation - transforming coordinate from on CRS to another.
Coordinate Conversion - converting a geodetic coordinate to a grid coordinate. Also used when converting units from one type to another (i.e. feet to meters).

Converting Between Geodetic (Latitude/Longitude) and Rectangular Coordinates (Y/X)

One you have defined a CRS, converting between geodetic and rectangular coordinates is pretty strait forward in TPC.

In the Traverse View, choose View | Format View.
Click the Advance tab and turn on 'Compute Latitude / Longitude' and return to the Traverse View.

This option tells the Traverse View to treat geodetic coordinates like raw data and compute the rectangular coordinates based on the current CRS for the survey. Because the geodetic coordinates are stored like any other raw data, you can chance the CRS or any of its parameters and TPC will re-compute the rectangular coordinates.

Entering Latitude and Longitude

Enter Latitude positive = North, negative = South or include the letter N before or after the value for North or the letter S before or after the value for South. Example: enter N42.1334568 for 42°13’34.568” North.

Enter Longitude positive=East, negative=West or include the letter W before or after the value for West or the letter E before or after the value for East. Example: enter W128.1334568 for 128°13’34.568” West.

Transforming a Survey From One Coordinate Reference System to Another

TPC can transform a survey from one CRS to another. To do this, it converts each grid coordinate to a geodetic coordinate (based on the existing CRS for the survey) then using the new CRS you have selected, it converts the same geodetic coordinate to a new rectangular coordinate.

TPC does not currently do any datum shifts, so you may need to translate the survey after the transformation to shift the rectangular coordinates appropriately. This is always true for instance, when converting between NAD83 (1986) (Conus) and NAD27. Once you have transformed and translated the survey, any rectangular coordinnate should produce the correct geodetic coordinate in the new CRS.

Editions

Premium, Professional