<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><br></div><div>Hi All,</div><div><br></div><div>usually i need to reproject Italian data</div><div> </div><div>from</div><div>Gauss Boaga rRome 40 </div><div><br></div><div>to </div><div>Wgs 84 </div><div><br></div><div>and inverse </div><div><br></div><div>when i need a good precision on a local scale extent, i use a set of control points (IGM95 vertex) </div><div>and apply last sqare methods to perform 2 different geometrics transformation :</div><div><br></div><div>1) conforme transformation (4 parameters valid for only planimetry) -> </div><div><br></div><div>Tx (longitude - tanslation) </div><div>Ty (latitude - translation) </div><div>λ (scale factor) </div><div>α (rigid rotation)</div><div><br></div><div>2) affine transformation (6 parameters valid for only planimetry) -></div><div><br></div><div>Tx (longitude - tanslation) </div><div>Ty (latitude - translation) </div><div>λx (longitude scale factor) </div><div>λy (latitude scale factor) </div><div>α (rigid rotation) </div><div>ϒ (angular sliding)</div><div><br></div><div><br></div><div>to transform vector files i apply the transformation parameters using pythn-gdal</div><div>but maybe (really i don't know) ...</div><div>it is possible to use these params directly in proj </div><div>(like we can do with cs2cs or including it inside an epsg code?)</div><div><br></div><div>...</div><div><br></div><div>an oher question :-/ ...</div><div><br></div><div>when i don't need more acuracy i use the follow +towgs params :</div><div><div><br></div><div><div>all the Italian region :</div><div><br></div><div><span class="Apple-style-span" style="font-size: 10px; "><i>towgs84</i> =<span style="font: normal normal normal 12px/normal Helvetica; "> <span class="Apple-style-span" style="font-size: 10px; ">−225.000,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>−65.000,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>9.000<span style="font: normal normal normal 12px/normal Helvetica; "> </span></span></span></span></div><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 10px/normal Helvetica; "><font class="Apple-style-span" size="3"><br></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 10px/normal Helvetica; "><font class="Apple-style-span" size="3">Italian peninsular part :</font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 10px/normal Helvetica; "><font class="Apple-style-span" size="3"><br></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 10px/normal Helvetica; "><font class="Apple-style-span" size="3"><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 10px/normal Helvetica; "><i>towgs</i><span style="font: normal normal normal 12px/normal Helvetica; "> </span>:<span style="font: normal normal normal 12px/normal Helvetica; "> <span class="Apple-style-span" style="font-size: 10px; ">−104.1,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>−49.1,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>−9.9,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>0.971,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>−2.917,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>0.714,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>−11.68<span style="font: normal normal normal 12px/normal Helvetica; "> </span></span></span></div><div><br></div><div>Sardinia :</div><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 10px/normal Helvetica; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 10px/normal Helvetica; "><i>towgs84</i> =<span style="font: normal normal normal 12px/normal Helvetica; "> <span class="Apple-style-span" style="font-size: 10px; ">−168.6,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>−34.0,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>38.6,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>−0.374,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>−0.679,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>−1.379,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>−9.48<span style="font: normal normal normal 12px/normal Helvetica; "> </span></span></span></div><div><br></div><div>Sicily :</div><div><br></div><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 10px/normal Helvetica; "><i>towgs84</i> =<span style="font: normal normal normal 12px/normal Helvetica; "> <span class="Apple-style-span" style="font-size: 10px; ">−50.2,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>−50.4,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>84.8,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>−0.690,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>−2.012,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>0.459,<span style="font: normal normal normal 12px/normal Helvetica; "> </span>−28.08<span style="font: normal normal normal 12px/normal Helvetica; "> </span></span></span></div><div><br></div></div></div></font></div></div></div><div>i have taken the above params directly from grass gis and i include it in the epsg file that come with the proj source code.</div><div>Using it inside the epsg code 3004 - 3003 the errors is drastically reduced.</div><div><br></div><div>.. my question :</div><div><br></div><div>instead of setting manually a customized projection,</div><div>is it possible to define new epsg code based on the +towgs paprameters inside the epsg file </div><div>and redistribuite it with the proj source code ?</div><div><br></div><div>... a lot of software student and newbie gis users can beneficiate of it.</div><div><br></div><div>i agree i can manually add it to the epsg file, but mybe there is a reason beacouse these parameters are not already inside it ?</div><div>a license problem ? </div><div><br></div><div>Thanks to All for any answers,</div></div><div><br></div><div><br></div><div>Massimo Di Stefano</div><div><div apple-content-edited="true"><span class="Apple-style-span" style="border-collapse: separate; 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"><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><a href="mailto:massimodisasha@yahoo.it">massimodisasha@yahoo.it</a></div><div><br></div><div>epifanio on irc.freenode.net /join gfoss</div><div><br></div></div></span><div><br></div><div><br></div><div><br></div></div></span></div></span></div></span></div></span><br class="Apple-interchange-newline"></div></span><br class="Apple-interchange-newline"> </div><br></div><br><br><div apple-content-edited="true"> <span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; 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line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>Massimo Di Stefano</div><div><a href="mailto:massimodisasha@yahoo.it">massimodisasha@yahoo.it</a></div><div><br></div><div>epifanio on irc.freenode.net /join gfoss</div><div><br></div></div></span><div><br></div><div><br></div><div><br></div></div></span></div></span></div></span></div></span><br class="Apple-interchange-newline"></div></span><br class="Apple-interchange-newline"> </div><br></body></html>