<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /></head><body style='font-size: 10pt'>
<p>Hello,</p>
<p><br /></p>
<p>1) if you do not specify any datum you have so called "floating datum" ... meaning that it will be in what ever datum the library thinks is most suitable for the situation. It will and should not assume any datum if it is not given ... this is better behaviour (than assuming WGS84 as it used to be, which created problems, jumps, and misunderstandings)</p>
<p><br /></p>
<p>2) see above (it used to be default ... but it was removed since it created strange shifts (jumps)) -- for example large maps do not care about datums since smallest details available (at one pixel scale) are much larger than largest datum shifts anywhere used!</p>
<p><br /></p>
<p>Janne.</p>
<p><br /></p>
<p>----------------------------------</p>
<p><br /></p>
<p>Nathan Woodrow kirjoitti 2019-01-22 00:59:</p>
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0">
<div dir="ltr">Hi,
<div> </div>
<span style="color: #263238; font-family: Roboto,sans-serif;">Now I'm just trying to understand mainly:</span>
<div><span style="color: #263238; font-family: Roboto,sans-serif;"> </span></div>
<div><span style="color: #263238; font-family: Roboto,sans-serif;">1) Why is </span><span style="color: #263238; font-family: Roboto,sans-serif; font-size: 13px;">+towgs84=0,0,0,0,0,0,0 needed on the target? As if it's not there it will just return the same values as the input</span></div>
<div><span style="color: #263238; font-family: Roboto,sans-serif;">2) Why is that not included as default? </span></div>
<div><span style="color: #263238; font-family: Roboto,sans-serif;">3) Is my understanding of the following correct? Proj is really doing: GDA94 -> WGS84 -> Shifted WGS84 via grid -> GDA2020?</span></div>
<div><span style="color: #263238; font-family: Roboto,sans-serif;"> </span></div>
<div><span style="color: #263238; font-family: Roboto,sans-serif;">Thanks,</span></div>
<div><span style="color: #263238; font-family: Roboto,sans-serif;">Nathan</span></div>
<div> </div>
</div>
</blockquote>
</body></html>