<br><br><div><span class="gmail_quote">2007/3/1, Oscar van Vlijmen <<a href="mailto:ovv@hetnet.nl">ovv@hetnet.nl</a>>:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
> From: "Andreas Rappensperger" <<a href="mailto:andreas.rappensperger@googlemail.com">andreas.rappensperger@googlemail.com</a>><br>> Date: Tue, 27 Feb 2007 15:12:05 +0100<br>> Subject: [Proj] Dubai Palm Island Projection
<br><br>> I have the following problem. I would like to rotate the Dubai Palm Island so<br>> that the palm stand vertical. The rotation point should be the middle point<br>> of the Palm. In Dubai usually the DLTM projection is used.
<br>...<br>> Now I tried to define my own coordinate system with the following parameter:<br>> # DP Dubai Palm (DLTM rotated by -49 degree)<br>> proj=omerc lat_0=25.095311 lonc=55.137296 alpha=-49.0000000<br>> k=
1.000000 x_0=500000.000 y_0=0.000 ellps=WGS84 units=m<br>> But it does not work. I have created a test. I have taken two points<br>> Bottom of the Palm: 55.154200° 25.102206°<br>> Top of the Palm: 55.122691° 25.126338°
<br>...<br><br>Try the no_rot option, then you'll stay in u,v coordinates, which are with<br>respect to the central line.<br>With your data I got an angle of -0.93 deg (atan2 of top minus bottom u,v<br>coordinates). That's nice because the geodesic azimuth angle between
<br>top->bottom is not -49 deg but actually -49.923 deg.</blockquote><div><br>
<p class="MsoNormal"><span style="" lang="EN-GB"><br>
Thanks a lot Oscar. The "no_rot" parameter was very helpful for me. <br>I am using these
parameters for me Dubai Palm projection now:</span></p>
<ul><li><span style="font-family: Symbol;" lang="EN-GB"><span style="">·<span style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
</span></span></span><span style="" lang="EN-GB">proj=omerc
</span><span style="font-family: Symbol;" lang="EN-GB"><span style=""><br></span></span></li><li><span style="font-family: Symbol;" lang="EN-GB"><span style="">·<span style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
</span></span></span><span style="" lang="EN-GB">lat_0=25.095311
</span></li><li><span style="font-family: Symbol;" lang="EN-GB"><span style="">·<span style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
</span></span></span><span style="" lang="EN-GB">lonc=55.137296
</span></li><li><span style="font-family: Symbol;" lang="EN-GB"><span style="">·<span style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
</span></span></span><span style="" lang="EN-GB">alpha=-49.5
</span></li><li><span style="font-family: Symbol;" lang="EN-GB"><span style="">·<span style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
</span></span></span><span style="" lang="EN-GB">k=1.000000
</span></li><li><span style="font-family: Symbol;" lang="EN-GB"><span style="">·<span style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
</span></span></span><span style="" lang="EN-GB">x_0=100000.000
</span></li><li><span style="font-family: Symbol;" lang="EN-GB"><span style="">·<span style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
</span></span></span><span style="" lang="EN-GB">y_0=100000.000
</span></li><li><span style="font-family: Symbol;" lang="EN-GB"><span style="">·<span style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
</span></span></span><span style="" lang="EN-GB">ellps=WGS84
</span></li><li><span style="font-family: Symbol;" lang="EN-GB"><span style="">·<span style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
</span></span></span><span style="" lang="EN-GB">units=m
</span></li><li><span style="font-family: Symbol;" lang="EN-GB"><span style="">·<span style="font-family: "Times New Roman"; font-style: normal; font-variant: normal; font-weight: normal; font-size: 7pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
</span></span></span><span style="" lang="EN-GB">no_rot</span></li></ul>
<p class="MsoNormal"><span style="" lang="EN-GB">But now I
am facing with another problem.<br>
I have got a satellite image projected in DLTM with this tfw file
parameters.</span></p>
<ul><li><span style="" lang="EN-GB">1.00000000000000</span></li><li><span style="" lang="EN-GB">0.00000000000000</span></li><li><span style="" lang="EN-GB">0.00000000000000</span></li><li><span style="" lang="EN-GB">-1.00000000000000
</span></li><li><span style="" lang="EN-GB">474701.80520413298000</span></li><li><span style="" lang="EN-GB">2782373.47255233210000</span></li></ul><p class="MsoNormal"><span style="" lang="EN-GB">Now I have transformed
the upper left corner to WGS84 and then to my Dubai Palm Jumeirah (DPJ) coordinate
system.</span></p><ul><li><span style="" lang="EN-GB">DLTM:
474701.805<span style=""> </span>2782373.472</span></li><li><span style="" lang="EN-GB">WGS84:
55.082433 25.147108 </span></li><li><span style="" lang="EN-GB">DPJ:
107933.554 100771.284</span></li></ul>
<p class="MsoNormal"><span style="" lang="EN-GB">Then I have
rotated the image though the middle point by 49.5° with GIMP and created a new
tfw file with the upper left corner in DPJ system. With these two file I have
created a web mapping sever with the rotated image.<span style=""> </span></span></p>
<p class="MsoNormal"><span style="" lang="EN-GB">The Problem
is now when I take any point of the rotated image and transform it back to WGS84
then it is completely wrong. I have transformed the bottom, top, left and right
point of the palm and it seams that the coordinates in the still rotated in WGS84.
</span></p><p class="MsoNormal"><span style="" lang="EN-GB">Do you have
an idea what I did wrong? </span></p>
<p class="MsoNormal"><span style="" lang="EN-GB">Should I use
the towgs84 parameter? </span></p>
<p class="MsoNormal"><span style="" lang="EN-GB"> </span></p>
<br><br></div><br></div>