I notice several EPSG codes in one WKT. At the first glance it almost is non-intuitive to see so many EPSG codes linked to a single EPSG.
Can someone explain each line of the following WKTs for EPSG:5070 and EPSG:4326?
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5ESPG is not just for the coordinate system. Each component has a code. The first two codes in your 1st example are for the spheroid GRS 80 EPSG 7019 and the datum NAD 83 EPSG 6269.– user2856Nov 9, 2020 at 11:54
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It might help to check this page and follow the links epsg.org/crs_5070/NAD83-Conus-Albers.html? The manual of the web app epsg.org/template/IOGP/downloads/user_manual_v5.2.1.pdf could be useful as well.– user30184Nov 9, 2020 at 13:47
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1 Answer
For a full understanding see the specifications:
https://www.ogc.org/standards/wkt-crs
Interestingly, if you look at the EPSG registry (https://epsg.org/home.html) WKT2 definitions of those two CRS then you see that almost every line has an associated EPSG code
https://epsg.org/crs/wkt/id/5070
PROJCRS["NAD83 / Conus Albers",
BASEGEOGCRS["NAD83",
DATUM["North American Datum 1983",
ELLIPSOID["GRS 1980",6378137,298.257222101,
LENGTHUNIT["metre",1,ID["EPSG",9001]],
ID["EPSG",7019]],
ID["EPSG",6269]],
PRIMEM["Greenwich",0,
ANGLEUNIT["degree",0.0174532925199433,ID["EPSG",9102]],
ID["EPSG",8901]],
ID["EPSG",4269]],
CONVERSION["Conus Albers",
METHOD["Albers Equal Area",
ID["EPSG",9822]],
PARAMETER["Latitude of false origin",23,
ANGLEUNIT["degree",0.0174532925199433,ID["EPSG",9102]]],
PARAMETER["Longitude of false origin",-96,
ANGLEUNIT["degree",0.0174532925199433,ID["EPSG",9102]]],
PARAMETER["Latitude of 1st standard parallel",29.5,
ANGLEUNIT["degree",0.0174532925199433,ID["EPSG",9102]]],
PARAMETER["Latitude of 2nd standard parallel",45.5,
ANGLEUNIT["degree",0.0174532925199433,ID["EPSG",9102]]],
PARAMETER["Easting at false origin",0,
LENGTHUNIT["metre",1,ID["EPSG",9001]]],
PARAMETER["Northing at false origin",0,
LENGTHUNIT["metre",1,ID["EPSG",9001]]],
ID["EPSG",5068]],
CS[Cartesian,2,
ID["EPSG",4499]],
AXIS["Easting (X)",east,
ORDER[1]],
AXIS["Northing (Y)",north,
ORDER[2]],
LENGTHUNIT["metre",1,ID["EPSG",9001]],
USAGE[SCOPE["Data analysis and small scale data presentation for contiguous lower 48 states."],AREA["United States (USA) - CONUS onshore - Alabama; Arizona; Arkansas; California; Colorado; Connecticut; Delaware; Florida; Georgia; Idaho; Illinois; Indiana; Iowa; Kansas; Kentucky; Louisiana; Maine; Maryland; Massachusetts; Michigan; Minnesota; Mississippi; Missouri; Montana; Nebraska; Nevada; New Hampshire; New Jersey; New Mexico; New York; North Carolina; North Dakota; Ohio; Oklahoma; Oregon; Pennsylvania; Rhode Island; South Carolina; South Dakota; Tennessee; Texas; Utah; Vermont; Virginia; Washington; West Virginia; Wisconsin; Wyoming."],
BBOX[24.41,-124.79,49.38,-66.91]],
ID["EPSG",5070]]
https://epsg.org/crs/wkt/id/4326
GEOGCRS["WGS 84",
ENSEMBLE["World Geodetic System 1984 ensemble",
MEMBER["World Geodetic System 1984 (Transit)",
ID["EPSG",1166]],
MEMBER["World Geodetic System 1984 (G730)",
ID["EPSG",1152]],
MEMBER["World Geodetic System 1984 (G873)",
ID["EPSG",1153]],
MEMBER["World Geodetic System 1984 (G1150)",
ID["EPSG",1154]],
MEMBER["World Geodetic System 1984 (G1674)",
ID["EPSG",1155]],
MEMBER["World Geodetic System 1984 (G1762)",
ID["EPSG",1156]],
ELLIPSOID["WGS 84",6378137,298.257223563,
LENGTHUNIT["metre",1,ID["EPSG",9001]],
ID["EPSG",7030]],
ENSEMBLEACCURACY[2],
ID["EPSG",6326]],
PRIMEM["Greenwich",0,
ANGLEUNIT["degree",0.0174532925199433,ID["EPSG",9102]],
ID["EPSG",8901]],
CS[ellipsoidal,2,
ID["EPSG",6422]],
AXIS["Geodetic latitude (Lat)",north,
ORDER[1]],
AXIS["Geodetic longitude (Lon)",east,
ORDER[2]],
ANGLEUNIT["degree (supplier to define representation)",0.0174532925199433,ID["EPSG",9122]],
USAGE[SCOPE["Horizontal component of 3D system."],AREA["World."],
BBOX[-90.00,-180.00,90.00,180.00]],
ID["EPSG",4326]]
You can look-up the respective codes in the registry for example EPSG",9122 is a transformation (NAD83(CSRS)v2 to NAD83(CSRS)v4 (1)): https://epsg.org/transformation/wkt/id/9122
