Creating Vector Overlays and Maps from the CIA Coastline Database in ENVI Classic

Note:  This Help Article is relevant to ENVI 5.0 Classic.

IDL, the language in which ENVI was written, is distributed with the CIA’s database of world coastlines and political boundaries. Beginning with the 3.0 release of ENVI, users can directly access the high or low resolution map databases to create vector layers and maps.

To access the CIA world coastline database in ENVI, bring up the Available Vectors List [ Vector -> Available Vectors List] and then within the Available Vectors List dialog select Options > Create World Boundaries... . The resulting dialog window will list the available databases from which you can create vector layers. You will be able to choose from Political Boundaries, Coastlines, Rivers, and USA States or any combination.

Note that some of the selections may be grayed out depending on which coastline database you selected when you installed ENVI. The default ENVI installation installs only the low resolution database. If you choose a custom configuration when you install ENVI, you have the option to also install the high resolution database.

You can save the new evf vector layers of this data to memory if you wish. However, if you intend to use them frequently you will find it more convenient to save them to disk. The EVF files generated from the low resolution database are quite small (less than 400 KB in total); the EVF files generated from the high resolution database are significantly larger (45 MB).

If you want to create vector layers from the version of the database that you did not install (for example you chose the default installation but want the high resolution vector layers), all you need to do is temporarily copy the database files from your installation CD-ROM to the ENVI you installed on your system. You'll find the coastline database files on the CD in:

...setup\x86\rsi\IDL56\resource\maps\

Note: On UNIX you must re-install the software.

This directory contains 2 subdirectories called " high" and "low" which contain the files for the two coastline databases. Simply copy the entire directory and all of its files into the corresponding directory under the ENVI/IDL installation on your system. For example, on a Windows machine, the appropriate destination directory under a typical installation of ENVI would be:

C:\Rsi\IDL56\resource\maps\

Then, follow the steps outlined above for building the vector layers in ENVI and you should have access to the additional database. After you create the vector layers (i.e., the .evf files), you can delete the extra database files to save disk space.

A simple way to make maps with these layers is to create a new, empty, georeferenced image file, then overlay the vector layers and grid lines. Using this method you will need to know some basic information about the map coverage you wish to make so that you can define the georeferencing information correctly (because the extent of the map coverage will be defined by a combination of the image size and the pixel size). For example, to make a map of Australia in a Lambert Conformal Conic projection:

1) make an empty image

- [ File -> Generate Test Data]
- select 'Constant', value = 0, samples = 500, lines = 350, bands = 1, data type = byte
- save the image to either memory or file

2) define the map projection and coverage

- [ File -> Edit ENVI Header], select the new, empty image
- under Edit Attributes, select Map Info
- Image Coord X and Y [1,1]
- Pixel Size X and Y [20000,20000]
- Projection = Lamberts Conformal Conic
- Lat = -2, Lon = 108

3) display the image and overlay coastlines

- from the image window menu select Overlay -> Vectors...
- in the Vector Parameters dialog, open the vector file created previously (using either the File menu to Open it or the Options menu to Import it)

4) add grid lines: from the image window menu select Overlay > Grid Lines...

5) add other annotations as desired [ Overlay -> Annotation...]

The displayed image on this page is an example created in ENVI using the high resolution coastline database.