Commonly Asked Questions
- How do I install JJFMapper
- What map projections does JJFMapper support
- What file formats does JJFMapper support
- What system is used for the version numbers
- What version should I use
- Can JJFMapper convert between different datums
- What does JJFMapper require
- Who should use JJFMapper
- Does JJFMapper work on Macintosh
- How do I install JJFMapper
- Download the latest release archive from the SourceForge project page, or
do a cvs-checkout. JJFMapper is a PHP script and therefore does not need to
be compiled. Do not install JJFMapper in your web share.
JJFMapper is designed to be included by other PHP scripts, and so installing
the program in your public webspace is unnecessary, and could be a security
risk. If you are installing it to a personal website on a remote webhost, you
could put it in your home directory, rather than your public_html directory.
If you are installing JJFMapper on your own computer you might choose a
location like /usr/local/jjfmapper (Linux) or c:\jjfmapper (Windows).
You will want to obtain ESRI Shapefiles of the features you want to map, and
put them into the 'geography' directory under the jjfmapper root. If you want
to store your geographic data in another location, you can reconfigure the
default by editing config.php in the JJFMapper root.
If you want to use the caching feature of JJFMapper, you need to set the
permissions of the 'cache' directory so that your web server has read and
write access to it. Under Linux you would change to the jjfmapper root
directory and do 'chmod 777 cache'.
- What map projections does JJFMapper support
- For now only one. A projection similar to Mercatur. In consideration of
speed, the projection class applies a uniform distortion to all longitude
coordinates. The factor of distortion is the cosine of the latitude in the
middle of the map. This means that there will be comparatively less
distortion when mapping a small area of the earth than when mapping a large
one.
- What file formats does JJFMapper support
- ESRI Shapefile
- Shapefile is not complete but it is getting close. JJFMapper currently
supports shapefiles that use the polygon shape type and the point shape
type.
- GPX
- JJFMapper supports GPX format.
- Coordinate List
- Coordinate List is a file format that I made up. It is a text file in
which each line contains a set of latitude/longitude coordinates. The
coordinates are parsed by the class Coordial (in coordial.php) which allows
for very flexible formatting. These files are extremely easy to generate on
the fly in a script, and so are well suited for working with a dataset of
geographic waypoints.
- What system is used for the version numbers
- The version of JJFMapper is a simple integer. The current system of assigning
version numbers is that I increment the version and create a distribution
archive when I decide that the project has reached a milestone.
- What version should I use
- Please use the current CVS version of JJFMapper, rather than the current
release version (13). I hope to have a release archive of version 14 soon.
- Can JJFMapper convert between different datums
- No. I decided that the cost in performance under PHP outweighed the benefit
of pixel-perfect plotting.
- What does JJFMapper require
- PHP
- JJFMapper was made to be compatible with PHP 4.2.3 and up. Note that the
PHP developers strongly recommend that everyone run at least version 4.3.10
because of critical security fixes.
- GD
- You must have the GD Module for PHP. JJFMapper will work with version 1
or 2 of this module, though some features are only available with GD2. (And
some require GD2.01.)
- Who should use JJFMapper
- Making maps is, by definition, a very resource intensive task. JJFMapper is
written in PHP, a scripting language designed for ease of use in handling
(primarily) html documents, rather than speed for tasks like graphics
manipulation and processing of binary data. JJFMapper is designed for people
who need simple maps in a PHP environment. If you need complicated maps
and/or can install and run cgi-binary programs on your webserver, a program
like Mapserver from the University of
Minnesota may better meet your needs.
- Does JJFMapper work on Macintosh
- Yes, but slower than on PC. JJFMapper uses PHP's unpack function to parse the
binary data in shapefiles. Unpack is not capable of changing the
byte-endianness of floating point numbers. Therefore JJFMapper has to use a
clumbsy workaround when it is run on big-endian machines. The best solution
for people who want to use JJFMapper on a big-endian machine is to
structure the site so that the maps can be pregenerated and cached to disk.
