[Proj] Proj API feature requests

Judd Taylor judd at seas.marine.usf.edu
Thu Apr 22 13:16:18 EDT 2004

    I've been using the proj library through the C API for a couple of years
now. Although I like the simplicity of the API, a couple of extensions would
be useful to make some of the command line tool's functionality available in
C code without having to parse the command line tool's output.
    Here's a list of what features would have made my life easier in the
past, and a couple of things that would make things easy enough that I could
add more functionality to my programs:
    1. Verbose configuraion information, similar to cmdline's '-v' (to be
used to generate FGDC compliant metadata).
    2. Per-point characteristics, similar to cmdline's '-V'
    3. Error estimation similar to cmdline's '-S' option.
    4. Querying through the API of available projections and their
information, as well cartesian units querying, similar to the cmdline's
'-l', '-lP', '-lu', and '-le' options.

    Returning strings would work in a pinch, but it would be nice to get
direct access to the data structures that hold this information. After a
quick look at projects.h, it looks like the interesting structs are going to
PJ_PRIME_MERIDIANS, FACTORS. Of course, direct access to the structs via the
API makes might break backwards-compatibility if they change down the
road... so maybe something else may work better.
    For #2-3 above, a seperate function for pj_fwd(), pj_inv(), etc... would
be nice as the extended information would be available, but if you don't
want it you could just call the normal functions which should be faster.

    Any thoughts/ideas/volunteers?


Judd Taylor
Computer Research Specialist
Institute for Marine Remote Sensing
University of South Florida
140 7th Ave. South
St Petersburg, FL 33701
(727) 553-1186
(727) 553-1103 (fax)
judd at marine.usf.edu

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