Appropriate equal-area cylindrical projection for Southeast Asia?

Question

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Background

I am facing difficulty in selecting an appropriate equal-area map projection suitable for the geographical extent of Southeast Asia. The main resource I am consulting is Savric et al's paper in 2016 titled 'Projection Wizard – An Online Map Projection Selection Tool' and the accompanying web-based tool (https://projectionwizard.org/). The geographical extent of Southeast Asia is 92.1892776489258949,-11.0097208023069015 : 141.0117645263674149,28.5432605743409908 (in decimal degrees). I plotted a similar extent at Projection Wizard, and the results show that only one projection is suitable;

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Projection details

Equal-area projection for regional maps with an east-west extent

Cylindrical equal-area PROJ.4

Standard parallel: 00º 00' N

Central meridian: 116º 06' E

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My question

However, I am not entirely sure how to use this result. It sounds like this means I will have to create my own custom projection (using the standard parrallel and central meridian identified by Projection Wizard) in PROJ4 program, which I am not familiar with yet.

Is there an EPSG projection equivalent that achieves similar results?

Answer 1

The wizard suggests the Lambert equal-area cylindrical projection whose distortion does not change with the choice of central meridian. The projection is a cartographically sound choice for your area, and thanks to the independence to the central meridian, you can use any global system that uses the projection in normal form with a zero standard parallel. The proj4 projection string is +proj=cea.

Unfortunately, the only EPSG system that contains CEA seems to be EPSG:6933 (WGS 84 / NSIDC EASE-Grid 2.0 Global), which uses stanadard parallels (latitudes of true scale) of +-30°, resulting in somewhat more distortion if you want to stick to standard systems only.

If you decide to proceed with your own projection, it is quite easy to modify the definitions from above to use zero latitude of true scale (in Proj4 and OGC WKT respectively):

+proj=cea +lon_0=0 +lat_ts=0 +x_0=0 +y_0=0 +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs

PROJCS["Your Projection Name",
    GEOGCS["WGS 84",
        DATUM["WGS_1984",
            SPHEROID["WGS 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],
            TOWGS84[0,0,0,0,0,0,0],
            AUTHORITY["EPSG","6326"]
        ],
        PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],
        UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9108"]],
        AUTHORITY["EPSG","4326"]
    ],
    PROJECTION["Cylindrical_Equal_Area"],
    PARAMETER["standard_parallel_1",0],
    PARAMETER["central_meridian",0],
    PARAMETER["false_easting",0],
    PARAMETER["false_northing",0],
    UNIT["Meter",1]
]