Jeff,
Most of us let a client-side (browser) JavaScript library like
OpenLayers handle the screen <-> projection calculation (among a lot of
other things). have a look at GeoMoose (http://www.geomoose.org) as a
framework to bring together the server-side and client-side components.
Best Regards,
Brent Fraser
On 7/5/2012 4:13 PM, Jeff Lake wrote:
Thanks for the reply ...
Lets ask this ..
I am setting up an open source weather mapping application (php)
I already know most of my target audience will not be able to install
MapServer and or proj4.
I have been trying to get a handle on various map projection's.
decided to use 3
Grid (or flat non-projected)
Mercator
and Lambert Conformal Conic
The first 2 was easy enough creating the needed Classes
to convert Lat/Long to screen pixel X/Y
Lambert has me lost ... every script I have found
be it C, perl, python, or php all return me X/Y in meter's
but for the life of me .. I cannot or have not found the magic
formula to convert the meter's to screen X/Y
I have looked at gPoint, PHPproj4, but they all go no further
then meter's (or it at least seems like it)
-Jeff Lake
MichiganWxSystem.com
WeatherMichigan.net
TheWeatherCenter.net
GRLevelXStuff.com
On 7/4/2012 9:31, Brent Fraser wrote:
Jeff,
World files use projected x/y coordinates. Use the Proj4 library
functions (in Mapscript) to project the upper left and lower right
spherical lon/lat coordinates to x/y, then use the image size
(length, width) to calculate the values for the world file
(http://en.wikipedia.org/wiki/World_file)
Best Regards,
Brent Fraser
On 7/3/2012 8:27 PM, Jeff Lake wrote:
Maybe I'm not searching on the correct terms.
But what is the magic formula for creating world files ??
I have a map of the US with the following projection info
ullat=53.3638
ullon=-130.964
lrlat=18.2977
lrlon=-69.1058
sp1=0
sp2=39
cm=-95.5
rlat=36.5
width=640
height=480
projection=lambert
now how on earth do you figure the meter per pixel??
prefer php, but guess I could convert
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