<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;
mso-fareast-language:EN-US;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#0563C1;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:#954F72;
text-decoration:underline;}
p.MsoListParagraph, li.MsoListParagraph, div.MsoListParagraph
{mso-style-priority:34;
margin-top:0cm;
margin-right:0cm;
margin-bottom:0cm;
margin-left:36.0pt;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;
mso-fareast-language:EN-US;}
span.EmailStyle18
{mso-style-type:personal-compose;
font-family:"Calibri",sans-serif;
color:windowtext;}
span.EmailStyle19
{mso-style-type:personal;
font-family:"Calibri",sans-serif;
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;
font-family:"Calibri",sans-serif;
mso-fareast-language:EN-US;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:70.85pt 70.85pt 70.85pt 70.85pt;}
div.WordSection1
{page:WordSection1;}
/* List Definitions */
@list l0
{mso-list-id:925500430;
mso-list-type:hybrid;
mso-list-template-ids:-1189818776 1512874658 68419609 68419611 68419599 68419609 68419611 68419599 68419609 68419611;}
@list l0:level1
{mso-level-text:"%1\)";
mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:20.4pt;
text-indent:-18.0pt;}
@list l0:level2
{mso-level-number-format:alpha-lower;
mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:56.4pt;
text-indent:-18.0pt;}
@list l0:level3
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
margin-left:92.4pt;
text-indent:-9.0pt;}
@list l0:level4
{mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:128.4pt;
text-indent:-18.0pt;}
@list l0:level5
{mso-level-number-format:alpha-lower;
mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:164.4pt;
text-indent:-18.0pt;}
@list l0:level6
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
margin-left:200.4pt;
text-indent:-9.0pt;}
@list l0:level7
{mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:236.4pt;
text-indent:-18.0pt;}
@list l0:level8
{mso-level-number-format:alpha-lower;
mso-level-tab-stop:none;
mso-level-number-position:left;
margin-left:272.4pt;
text-indent:-18.0pt;}
@list l0:level9
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
margin-left:308.4pt;
text-indent:-9.0pt;}
ol
{margin-bottom:0cm;}
ul
{margin-bottom:0cm;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="NO-BOK" link="#0563C1" vlink="#954F72">
<div class="WordSection1">
<p class="MsoNormal"><span lang="EN-US">Dear all,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Although there is a lot of relevant information regarding the orthorectification of tilted digital camera images in GRASS GIS online (here:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><a href="http://grasswiki.osgeo.org/wiki/Orthorectification_digital_camera">http://grasswiki.osgeo.org/wiki/Orthorectification_digital_camera</a><o:p></o:p></span></p>
<p class="MsoNormal"><a href="http://www.academia.edu/853401/Robust_rectification_of_aerial_photographs_in_an_open_source_environment"><span lang="EN-US">http://www.academia.edu/853401/Robust_rectification_of_aerial_photographs_in_an_open_source_environment</span></a><span lang="EN-US"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><a href="http://osgeo-org.1560.x6.nabble.com/rectifying-digital-images-td3929803.html">http://osgeo-org.1560.x6.nabble.com/rectifying-digital-images-td3929803.html</a><o:p></o:p></span></p>
<p class="MsoNormal"><a href="http://www.grassbook.org/wp-content/uploads/neteler/papers/neteler2005_IJG_051-061_draft.pdf"><span lang="EN-US">http://www.grassbook.org/wp-content/uploads/neteler/papers/neteler2005_IJG_051-061_draft.pdf</span></a><span lang="EN-US"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">and the module manuals of course), I am still struggling with applying the procedure to my example properly. The problem is that the image is either not enough or too much stretched and twisted and never matches with
the GCPs…<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I have an image taken with a wildlife camera trap which shows four color markers we placed in the terrain and measured using a handheld GPS (aiming at using those as GCPs). Camera position has been GPS-measured as well.
I do have a high resolution DEM (Lidar) for the area and enquired camera specs from the manufacturer (Reconyx) as the camera does not produce EXIF data...<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The camera has a fixed focal length of 8.5 mm, a sensor size of 4.8 x 6.4 mm with 1536 x 2048 pixels.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">So I defined 4 fiducial marks (starting clockwise from middle of the left border) as<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">In mm on the sensor<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">1 -3.2 0<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">2 0 2.4<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">3 3.2 0<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">4 0 -2.4<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Corresponding pixels on the image are defined as<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">1 0 768<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">2 1024 1536<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">3 2048 768<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">4 1024 0<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">RMS is 0.0<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">When it comes to defining initial camera exposure I get quite a bit unsure about my settings (and the camera exposure settings seem to have a significant effect on the results).<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">X,Y,Z should be OK, as they are measured by GPS/DEM OK.. The article here
</span><a href="http://www.grassbook.org/wp-content/uploads/neteler/papers/neteler2005_IJG_051-061_draft.pdf"><span lang="EN-US">http://www.grassbook.org/wp-content/uploads/neteler/papers/neteler2005_IJG_051-061_draft.pdf</span></a>
<span lang="EN-US">says roll, pitch and yaw can be estimated using d.measure.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The photo direction (“yaw”) should be ca. 270 degree as the picture is taken in towards east direction. But how do I estimate “pitch” and “roll”?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Given that the picture is taken slightly uphill (and even shows some sky) I tried 120 degree for “pitch”. But that worked equally bad as e.g. 90 or less… (I suspect “pitch” to be the main source of error)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I kept “roll” more or less constant at 0 as it was hard to guess.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Does up-slope direction of the photo or sky in the photo conflict with the orthorectification algorithm?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">When it comes to the GCPs I am in principle quite confident that they are placed OK. Or do you think that GCPs measured by a hand held GPS are too imprecise?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">However, depending on initial camera settings RMS something like 268, which indicates that something is wrong here. If I do not use i.photo.init, the image is placed much better (RMS around 10-20), but still pretty poor…<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I can provide the data if that helps and if someone would be willing to take a look at them after reading my long mail (sorry).<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Thanks for helping in advance,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Stefan <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Btw: Some of the submodules of i.ortho.photo are not linked to the /bin folder in GRASS 6.4.5svn, so I have to start them like this: /usr/local/grass-6.4.5svn/etc/i.photo.init<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
</div>
</body>
</html>