Hawaii Projection and Datum Transformation extension Version 02/04/2000 **************** Please let us know of any problems and desirable enhancements, via email to Richard Stone, rstone@aloha.net, phone (subject to change soon) 808-539-3773. After unzipping the file hidatum.zip, in addition to this readme file, you should have 3 files: hidatum.avx hawaii.dbf hawaii.prm Copy all 3 files to your ArcView Ext32 directory (normally C:\ESRI\AV_GIS30\ARCVIEW\EXT32 under Windows 95 and 98) Start ArcView. You should now have a listing in the Extensions dialog for this extension. Check it and a new button will appear at or near the right end of the View Button Bar. If the View has one active theme, click the button to bring up the Dialog. Click the Help button in the Dialog for further instructions (which are also reproduced below:) This extension has been tested under ArcView 3.2 and 3.1 on Windows 95, 98 and NT 4. (Not tested under Unix, but should work with minor modifications.) ******************************* HELP File (from Dialog Help button) (02/03/00) The Hawaii Projection and Datum Conversion extension allows you to select one of the common Hawaii projections and datums and convert to the other datum, or to another projection in the same datum. This extension incorporates scripts modified from two other extensions: ESRI's Projector! sample extension, and the NADCON extension created by Mark Cederholm from the NADCON datum conversion program of the National Geodetic Survey. The extension allows conversion between Old Hawaiian Datum and the NAD 1983 datum, in either direction. Supported projections are UTM zones 4 and 5, State Plane zones 1 through 5, and unprojected decimal degrees. For example, you can convert from Old Hawaiian UTM Zone 4 (the coordinate system of the State of Hawaii GIS) to NAD 1983 State Plane Zone 2 (the system used by Maui County's GIS). Or you could convert from Old Hawaiian UTM Zone 4 to Old Hawaiian State Plane Zone 3 (the system currently used by the City and County of Honolulu's HOLIS GIS). Only ESRI ArcView shapefiles can be converted (no GRIDs, images, CAD themes, or other theme types). Following are step-by-step instructions. Be sure to read the additional notes following the instructions. 1. Add the shapefile or files as themes in a view. All of the shapefiles must be in the same coordinate system. 2. The View's Map Units must be set in View Properties. 3. Make sure that ALL of these themes are made active (they don't have to be checked visible but must be active). Make certain that no other themes are active. 4. Click the button at or near the upper right of the button bar (the tool tip will say "Hawaii Projection and Datum Transform"). 6. You must know the current coordinate system of the shapefiles which you want to convert. Click on this coordinate system in the list box. 7. The output list box will appear. Click on the output coordinate system. 8. Click the Run button. If you are converting multiple files, you will be prompted for the name of a directory in which to put all the new shapefiles. This directory cannot contain any of the existing shapefiles or any file with the same name as one of these. The directory must exist before running the program. 9. You will be prompted to choose a View for displaying the output shapefiles. 10. If you are converting only one file, you will also be prompted for the name of this output shapefile. ADDITIONAL NOTES: This extension uses the NADCON method for datum transformations. This is the preferred method for any Hawaii datum shifts. Other methods, such as "3-parameter", "7-parameter", or "Molodensky", may produce errors of 5 meters or greater compared with NADCON. Many GPS software packages use one of the less accurate methods. "NADCON" stands for "North American Datum Conversion", a name which is misleading, since the Old Hawaiian Datum is not the same as the North American Datum of 1927. There are many erroneous references to "NAD 1927" which should say "Old Hawaiian Datum". However, no Hawaiian geographic data sources were ever created using NAD 1927. NADCON does convert Old Hawaiian Datum and a few other U.S. island datums in additon to NAD 1927. The new datum, NAD 1983, is in fact the same datum for both the continent and the islands. The WGS 1984 datum is essentially identical to NAD 1983. This program works only for the main Hawaiian islands and nearby ocean areas. If you get an "out of bounds" message, that means that the shapefile contains some data from beyond these areas. Multiple-shapefile processing: You will be prompted for a directory (folder) in which to write the output shapefiles. All output files will be written to this directory, and will be given the same file names as the input shapefiles. Therefore the output directory must not contain any file having the same name as an input file. NADCON datum transformation is not fast. Large files may take over an hour and therefore multiple file conversion may best be done overnight. For example, an 11 MB polygon shapefile took about 55 minutes on a 400 mhz machine with 96 MB of RAM. More powerful configurations produce substantially faster results. The transformation from Old Hawaiian to NAD 1983 is substantially faster than the reverse transformation. The program creates a "View for Messages" in the project. This provides a means for logging the progress of the program. There is no need to keep this view in your project after the conversion is finished. This message view may not refresh immediately when larger files are being converted. Note that the units available are the standard units for the various projections: Meters for UTM (Old Hawaiian or NAD 1983); feet for Old Hawaiian State Plane; and meters for NAD 1983 State Plane. If, after opening the Dialog, you need to return to the project for any reason, you should close the dialog, then restart it. Otherwise the view containing the shapefiles to be converted may not be the active document, and errors will result. You may notice that some temporary views and themes are created during the transformation process. These will be deleted automatically. If the process is aborted, these views and the temporary shapefiles will remain. The temporary shapefiles are in your $TEMP directory, whose location will appear when you view this from the Help button. If you want to use a less common projection for your Hawaii data, such as Albers, you can convert the shapefile to decimal degrees in Old Hawaiian or NAD 1983, and put it into a new View. You can then use the View projection button to make the projection, and, if desired, convert the projected shapefile to a shapefile in the less common projection.