How can I define a Mapping Toolbox stereographic projection using the information from a projection file (.prj) ?

I want to parse a projection (.prj) file and create a stereographic projection using the parameters from the projection file.

Answer 1

[MathWorks Support Team]

The ability to automatically parse a projection file and create a projection is not available in the Mapping Toolbox.

To work around this issue, you can manually parse the projection file and use the parameters to create a stereographic projection. For example, a stereographic projection file has the following contents:

 PROJCS["WGS_1984_Stereographic_South_Pole",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Stereographic_South_Pole"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",0.0],PARAMETER["Standard_Parallel_1",-71.0],UNIT["Meter",1.0]]

You can create a Mapping Toolbox stereographic projection structure from the parameters in the .prj file as follows:

mstereo = defaultm('stereo')

mstereo.geoid = [6378137.0, flat2ecc(1/298.257223563)] ; 

mstereo.falseeasting  = 0; 

mstereo.falsenorthing = 0; 

mstereo.nparallels = 1; 

mstereo.mapparallels = -71; 

mstereo.origin = [-90 0]; 

mstereo = defaultm(mstereo);

To use this projection structure to display latitude and longitude coastline vector data, you can use the following commands:

figure

axesm(mstereo)

load coast

plotm(lat, long)

To transform map coordinate data (given x,y coordinate arrays) to latitude and longitude, use:

[lat,lon] = minvtran(mstereo, x, y);

Answer 2

[Chad Greene]

Alternatively, with Antarctic Mapping Tools available on File Exchange, simply type

antmap

to initialize a southern hemisphere polar stereographic map. Andrew Roberts has a function called ncpolarm which is a northern hemisphere equivalent and it is available on File Exchange.

[Abhishek Pandey]

Hi Andrea

The ability to automatically parse a projection file and create a projection is still not available in the Mapping Toolbox. But if you have any specific questions, please contact MathWorks Technical Support and raise a help ticket. I am sure our team will be very happy to help you.

- Abhishek