Coordinate Transformation for Macau Data Using ArcGIS for Desktop

Transcription

1 Coordinate Transformation for Macau Data Using ArcGIS for Desktop Article ID : TT Software : ArcGIS 10.2 for Desktop Platform : Windows 7, Windows 8, Windows Server 2003, Windows Server 2008/R2 Date : 20 th February, 2014 Introduction The purpose of this article is to show the steps of converting Macau Digital Map Data from Macau Grid Coordinate System to WGS84 Coordinate System for users to work with GPS related technologies. The conversion requires coordinate transformation parameters which are documented in the Explanatory Notes on Geodetic Datums in Macao Special Administrative Region ( Procedures 1. Creating Projection File (*.prj) and Define projection for your data Projection file (*.prj) is necessary to define coordinate system of GIS data and all data should have a projection file associated with prior to carry out coordinate transformation. To create a new projection file for Macau Grid, follow below steps: 1) Open ArcCatalog, go to Toolboxes > System Toolboxes > Data Management Tools > Projections and Transformations. All rights reserved. P. 1 of 8

2 2) Open Define Projection Tool. Click the button next to the text box under Coordinate System. 3) The Spatial Reference Properties dialog will open: All rights reserved. P. 2 of 8

3 4) Click the Globe button and select to new a Projected Coordinate System 5) The New Projected Coordinate System dialog will open, enter the Macau Grid Projection parameters according to the Explanatory Notes on Geodetic Datums in Macao Special Administrative Region or follow below screen: All rights reserved. P. 3 of 8

4 6) Then, click Change to change the Geographic Coordinate System: 7) Search for international and select International 1924 as the Geographic Coordinate System, click OK: 8) The Macau Grid Projection File will then be created under custom folder; you can now right click the Macau Grid Projection File and click Save As to save the file to your desired location for future use. The projection file is actually a text file that can be opened by Notepad and you can examine the parameters recorded inside: All rights reserved. P. 4 of 8

5 9) Click OK to close the Spatial Reference Properties. The Macau Grid is now defined in the toolbox. If you have Macau Data that need to be defined as Macau Grid Coordinate System, you can do so in the same toolbox by specifying the data location: 10) Click OK and your data will have its projection being defined as Macau Grid. All rights reserved. P. 5 of 8

6 2. Creating Custom Geographic Transformation After creating the projection file for Macau, the next step is to create geographic transformation for Macau using the transformation parameters specified in the Explanatory Notes on Geodetic Datums in Macao Special Administrative Region. To create Custom Geographic Coordinate Transformation, follow below steps: 11) Open ArcCatalog, go to Toolboxes > System Toolboxes > Data Management Tools > Projections and Transformations, click Create Custom Geographic Transformation to open the tool 12) Enter the details as follow: Select the method as MOLODENSKY_BADEKAS which is being used in Macau and enter the transformation parameters according to the Explanatory Notes on Geodetic Datums in Macao Special Administrative Region. All rights reserved. P. 6 of 8

7 13) Click OK to process and close the tool. The Custom Geographic Transformation will then be created and stored as file with extension *.gtf, the gtf file can be found in this location: C:\Users\<user profile>\appdata\roaming\esri\desktop10.2\arctoolbox\customtransformations, you can go to this location to copy and backup the gtf file for future use: 3. Projecting your data Once your Macau data has projection file defined and the geographic transformation is created, you are now ready to carry out coordinate transformation for your Macau Data. Please follow below steps: 14) Open ArcCatalog, go to Toolboxes > System Toolboxes > Data Management Tools > Projections and Transformations > Feature, click Project to open the tool All rights reserved. P. 7 of 8

8 15) The tool will open, specify your data, whenever your data has projection defined, it will be automatically recognized as Input Coordinate System. Define the output location of dataset or feature class, then choose the Output Coordinate System as GCS_WGS_1984 or select it via the Spatial Reference Properties, it can be located in this path: Geographic Coordinate System > World > WGS 1984: 16) As the Geographic Transformation is defined before, it will also be automatically recognized. 17) Click OK to process and close the tool. 18) The data will be converted and saved to your specified location. The End All rights reserved. P. 8 of 8