This is a newbie question that is about converting between wgs84 and nad83. I have aerial photos that I am trying to compute lat long coordinates for as closely as possible. There are several factors that make the usual types of corrections tricky, e.g. questionable parameters, ... so there is some trial and error involved.
Thus I need a way to check my progress as I make corrections. At first just checking against google earth was fine, but at this point the 2.5 foot or so difference between my data (nad83) and google earth(wgs84) has become a limiting factor. So I need to transform nad83 to wgs84.
I have been using rgdal in R and dotspatial in C# to do projections, but I think changing between nad83 and wgs84 isn't considered a "projection" (am I right?). Attempting to call project with "+proj=NAD83 ellps=WGS84" just throws an error.
I am fine with writing a 7 parameter coordinate change myself, except I am not sure how to convert either one to (X,Y,Z) coordinates (which I assume means converting from lat long to the surface of the ellipsoids they are based on). The existing questions on nad83 and wgs84 seem to be about which method to use, rather than answering a very basic question like mine, i.e. how does one do it at all?
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Thus I need a way to check my progress as I make corrections. At first just checking against google earth was fine, but at this point the 2.5 foot or so difference between my data (nad83) and google earth(wgs84) has become a limiting factor. So I need to transform nad83 to wgs84.
I have been using rgdal in R and dotspatial in C# to do projections, but I think changing between nad83 and wgs84 isn't considered a "projection" (am I right?). Attempting to call project with "+proj=NAD83 ellps=WGS84" just throws an error.
I am fine with writing a 7 parameter coordinate change myself, except I am not sure how to convert either one to (X,Y,Z) coordinates (which I assume means converting from lat long to the surface of the ellipsoids they are based on). The existing questions on nad83 and wgs84 seem to be about which method to use, rather than answering a very basic question like mine, i.e. how does one do it at all?
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