I have knowledge enough to play around Proj4s string but I have not found any question about this yet.
I have these two Proj4 strings.
+proj=eqdc +lat_0=39 +lon_0=-96 +lat_1=33 +lat_2=45 +x_0=0 +y_0=0 +ellps=GRS80 +towgs84=-0.9956,1.9013,0.5215,0.025915,0.009416,0.0011599,-0.00062 +units=m +no_defs
and this one below (
+datum=NAD83 is added in front of
+proj=eqdc +lat_0=39 +lon_0=-96 +lat_1=33 +lat_2=45 +x_0=0 +y_0=0 +datum=NAD83 +ellps=GRS80 +towgs84=-0.9956,1.9013,0.5215,0.025915,0.009416,0.0011599,-0.00062 +units=m +no_deft
In case you wonder, The 7-parameters argument in both strings is from this post.
I wonder if:
In the 2nd string, will
+datum=NAD83during transforming projection?
I have two file about the same data projected by 1st string and 2nd string. I am going to transform them to any NAD83-based projection or NAD83 latlong(EPSG-4269). Will Proj4 transform the data projected by 2nd string to the new NAD83-based projection with or without datum shift because I had
+datum=NAD83in the Proj4 string and in front of
2.1 After projecting 1st-string-projected data and 2nd-string-projected data to the same NAD83 projection, will or will not I have two same results?