Bangkok, Thailand

Transform Coordinates

Coordinate Transformation

The Transform Coordinate is designed to be the global coordinate transformation tool. It’s easy to use. The tool uses the Proj4 library as the engine so it can transform coordinates from any coordinate reference systems as many as the library can support.

When start Surveyor Pocket Tools you can see as the screenshot below, double click at the Transform Coordinates icon to run.

Transform Coordinates

The tool will be shown as the screenshot below. There are two panels on the left and right. The left and the right panel are the same function. You can input on the right panel and compute the results to be shown on the left panel.

You can set the coordinate reference system to the left panel or the right panel independent. At the middle there are two big buttons. The  button is represented the computation from left panel to right panel . The   button is represented the computation from right panel to left panel.

There are two vertical toolbar that packed four small icons that adjacent to the point definition on the left panel and the right panel. Here’s a detailed list of it’s function:

• The button use to store/save point to database.
• The  button use to restore point from database.
• The  button use to pin location to Google maps.
• The  button use to save KML file and display location on Google Earth.

The screenshot below shows three parts for each panel. The coordinate reference system on the top, the middle part is point definition to be computed or from conversion and transformation and the bottom part is a selection of angle display format for geodetic coordinate and convergence angle.

Working with Coordinate Reference Systems (CRS)

To specify the coordinate reference system definition you can do easily by the steps that provided by Surveyor Pocket Tools. Please follow the tutorial:

How to select a Coordinate System?

Define Display Formats and Input Geodetic Coordinates

There are many possible display formats for geographic or geodetic coordinates (latitude/longitude). Follow the link below for tutorial how to define angle display settings and input geodetic coordinates.

How to define angle display formats and input geodetic coordinates?

Coordinate Transformation between datums

The next examples will show how to complete the calculation with the tool using the given point coordinates.

Example 1 – Test on Universal Transverse Mercator Projection

Convert the position of station 0006-030 from its “Indian 1975 / UTM zone 47N” (Thailand). Grid Northing = 1597950.172m, Grid Easting = 703896.986m. Find the coordinates on “WGS84 / UTM zone 47N“.

Select the source coordinate system on the left panel as below. Please note when select the datum try to type the word “indian” and select from the new list.

Select the target coordinate system on the right panel as below.

Enter the coordinates value for the point to be converted into the left panel as the screenshot below. Ready to compute click the arrow icon.

The results of conversion will be displayed on the input and output panels.

The computation result shows as screenshot above. The target projected coordinates will be computed as the output on the right panel.

The output coordinates on “WGS84 / UTM zone 47N” are Grid Northing = 1598253.1777m, Grid Easting = 703564.2235m. Latitude = 14°26’57.42469″N, Longitude = 100°53’18.38612″E, Grid scale factor = 1.0001125682, Convergence = 0°28’16.92961″.

The geodetic coordinates, grid scale factor and convergence will be computed when a projected coordinate system was chosen as the input or output system as well.

Grid Scale Factor

Grid scale factor, sometimes called “Scale Factor” is measured of distortion at a point on the mapping plane or grid. Grid scale factor is the ratio of grid distances on the map to geodesic distances on the ellipsoid.

Convergence

Convergence is the angle at a point on a map between the directions of True North and Grid North.

Store the Point to Database and Restore the point from database

If you need to save a input or output point into database called Geo Database. Please follow the tutorial link:

How to use Geo Database?

Coordinate Conversion

You can use this tool to calculate the coordinate conversion on the same datum as well. The next example will show this feature.

Example 2 – Test on Oblique Mercator Projection

Given:

• Station: UV5754
• Datum: State Plane Coordinate System (SPC or SPCS) – NAD83 (National Spatial Reference System 2007)
• Coordinate System:  Alaska zone 1
• Projection : Oblique Mercator
• Geodetic coordinates: Latitude = 55º 6′ 45.20173″N, Longitude = 131º 43′ 58.97516″W

Find the projected coordinates on the Alaska zone 1.

Change the coordinate system of the left panel.

Change the coordinate system of the right panel.

Enter the coordinates value (latitude, longitude) into appropriate text boxes in the Point Definition.

Ready to calculate, click the  button. The results of the conversion will be displayed in the Point Definition of the right panel.

The results of coordinate conversion are Grid Northing = 366701.8435, Grid Easting = 942069.8596, Grid scale factor = 0.99999085667, Convergence = 1º36’31.76352″

Example 3 – Test on Lambert Conformal Conic Projection

Given:

• Projected Coordinate Reference System : Belge 1972 / Belge Lambert 1972
• Projection : Lambert Conformal Conic
• Geodetic coordinates : Latitude = 50º40’46.4610″N, Longitude = 5º48’26.533″E

Find the projected coordinates on the Belge Lambert 1972.

In this example the coordinates will be entered on the right panel and compute the results into the left panel.

Set the coordinate system on the right panel.

Set the coordinate system on the left panel for output.

Enter the coordinates value on the right panel at the appropriate  text boxes. Compute the result by click  button. The results will be displayed on the left panel. The projected coordinate system was chosen so the grid scale factor and covergence will be calculated.

The results of coordinate conversion are Grid Northing = 153034.1757, Grid Easting = 251763.2050, Grid scale factor = 0.9999373090, Convergence = 1°6’39.86981″

Limitations of Transform Coordinates

The Surveyor Pocket Tools is still the beta version so it cause some limitations:

• Not yet supported unit of measurement in foot, only meter you can use.
• Not yet supported Military Grid Reference System (MGRS).
• Gris Scale Factor & Convergence only supported for Oblique Mercator, Lambert Conformal Conic and Transverse Mercator projection.