Coordinate Transformations

Transforming Coordinates

TPC's coordinate transformation tools allow you to work 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 spherical surface to a flat surface).

Terminology

•Grid Coordinate - any X,Y coordinate value based on a rectangular coordinate system

•Coordinate Transformation

•transforming a coordinate to it's geodetic position or visa versa per a CRS

•transforming coordinates from one CRS to another CRS

•Coordinate Conversion - converting units from one type to another (i.e. feet to meters).

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

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

In the Point Manager

1.Choose View | Format View

2.Include coordinate and/or geodetic columns

3.Return to the Point Manager and TPC computes any missing transformations

In a Traverse View

1.Choose View | Format View

2.Click the Advance tab and turn on 'Compute Latitude / Longitude'

3.Return to the Traverse View and TPC computes any missing transformations

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 From One CRS to Another

TPC can transform a survey from one CRS to another. You do this with the Transform Coordinates Command and select what you want to transform from the What list.

You select a CRS to transform From and a CRS to transform To. TPC transforms each selected coordinate to a geodetic position using the From CRS, then back to a coordinate using the To CRS you have select.

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 coordinate should produce the correct geodetic coordinate in the new CRS.

Local CRS

This operations requires the current survey coordinates to be based on a CRS. Local coordinates like 5000/5000 are not valid for this operation and would need to be calibrated to a CRS instead.