Part 3—Use URL Shortcuts to Specify Map Areas
Step 1 – Familiarize Yourself with the Format for Using Shortcuts
If you know the latitude and longitude coordinates of a feature you want to map, you can go directly to that feature by adding coordinate values to the end of the URL.
The main Voyager URL for Earth is http://jules.unavco.org/Voyager/Earth
To specify the map you want:
- Add a question mark ? directly to the end of the URL in your browser's address window.
- Add key value pairs (described below) for the parameters you want to control.
- Separate each pair of key values from the next pair by an ampersand (&) symbol.
Enter each of the following examples in your browser and examine the resulting images. Every character in the URL counts, so type very carefully!
Step 2 – Specify the Center of a Map
If you know the lat/long coordinates of a feature, you can create a map centered on that feature.
where n=degrees of latitude north and e=degrees of longitude east
NOTE: Use negative values for west and south
The latitude and longitude coordinates for St. Petersburg, Florida are 27.763°N, 82.637°W
Therefore, the URL http://jules.unavco.org/Voyager/Earth?n=27.763&e=-82.637
produces a map centered on St. Petersburg, Florida.
Step 3 – Specify the Areal Coverage of a Map
If you know how much area you would like your map to cover, you can specify it in either degrees or kilometers.
where dn=degrees north and south of center
and de=degrees east and west of center
produces a map centered on St. Petersburg spanning a total of 10 degrees in a north-south direction (5 degrees north and 5 degrees south) and a total of 20 degrees in an east-west direction (10 degrees in each direction).
where kmn=kilometers north and south of center
and kme=kilometers east and west of center
produces a map centered on St. Petersburg that extends 200 km to the north and 200 km to the south of St. Petersburg (total of 400 km) and 400 km each to the east and the west (total of 800 km).
Step 4 – Specify the Width of a GIF Map Image
If you need a map of a certain width (in pixels), you can specify that width.
To produce images of a different width, add w=xxx to the URL where w=width in pixels.
produces a 400 x 800 km map of St. Petersburg that is 360 pixels wide.