Background

The New Orleans District supports distribution of hydrographic survey/ navigation data in MicroStation CADD Design File (DGN) format, which is our native data creation format. These DGN files may be downloaded in compressed (PKZIP) format in the tabular listing provided on each survey area WWW page. These design files are 3-dimensional with X-Y coordinates stored as survey feet in LOUISIANA STATE PLANE 1702 map grid projection. The Z-coordinate values (or elevations) are stored as feet in MEAN LOW GULF vertical datum. In April 1998, New Orleans District began providing preview graphics of the most current surveys in JPEG, CGM, and SVF formats for quick review. We are using a Netscape Server extension called Bentley Modelserver Publisher which "plots" our DGN files to the WWW in numerous file formats. The full DGN files should still be downloaded and plotted with via Bentley MicroStation or Bentley Powerscope if high quality D size/ E size sheets are required. NOTE: Other Commercial Off-the-Shelf CADD software and redlining tools may support viewing and plotting these files.)

JPEG Format

JPEG is a standardized image compression format designed for compressing photographic images. JPEG stands for Joint Photographic Experts Group. JPEG is not well suited for viewing our line drawing files. We do not recommend viewing our data in this format. We provide JPEG only because it can be displayed without an additional browser plug-in.

CGM Format

Computer Graphics Metafile (CGM) format is a zoomable vector/raster format with crisp resolution of text and graphics. CGM format data must be viewed using third party browser plugins. Visit the Bentley WWW site for data and links to downloadable CGM plugins.

SVF Format

Simple Vector Format(SVF) is a zoomable vector format with crisp resolution of text and graphics. It also supports turning data levels (layers) on and off. SVF format data must be viewed using third party browser plugins. Visit the Bentley WWW site for data and links to downloadable SVF plugins.

JAVA Graphic Viewing Applet

A Java applet is platform independent program code that resides on the WWW server and is downloaded to the browser when needed. The code is then compiled and executed within the browser's "Virtual Machine". Our survey data may be viewed via a Bentley ModelServer Viewer (JAVA) Applet, which we will download into your browswer. The advantage to using this applet is that it offers excellent zooming, panning, level control, and printing features. It also frees data users from having to download/install/purchase plugin software.