<HTML dir=ltr><HEAD><TITLE>Re: [Gvsig_english] Point2Point Comparison</TITLE>
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<DIV dir=ltr><FONT face="Times New Roman" color=#000000 size=3>Hello, Simon. </FONT><FONT face="Times New Roman" color=#000000 size=3>Starting from the DBF file you sent some days ago, you can do this:</FONT></DIV>
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<DIV dir=ltr><FONT face="Times New Roman" color=#000000 size=3>- Add the DBF file as a table in gvSIG</FONT></DIV>
<DIV dir=ltr><FONT face="Times New Roman" color=#000000 size=3>- Create an event theme (point layer) using for example the EPSG:4202 columns and save it as a shapefile</FONT></DIV>
<DIV dir=ltr><FONT face="Times New Roman" color=#000000 size=3>- Create a view in EPSG:4283 and add the previous shapefile (on-the-fly reprojection using the gsb file)</FONT></DIV>
<DIV dir=ltr><FONT face="Times New Roman" color=#000000 size=3>- Create two new columns of type DOUBLE (for example "new_lon" and "new_lat")</FONT></DIV>
<DIV dir=ltr><FONT face="Times New Roman" color=#000000 size=3>- With the field calculator, set those columns to the reprojected values using the functions x() and y()</FONT></DIV>
<DIV dir=ltr><FONT face="Times New Roman" color=#000000 size=3>- Now you can compare the resulting values with the EPSG:4283 columns your DBF file had from the start and were not used before</FONT></DIV>
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<DIV dir=ltr><FONT face="Times New Roman" color=#000000 size=3>The formulas for distance and bearing can be found easily. This nice website mentions two different formulas and says one of them is not very good for very small distances:</FONT></DIV>
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<DIV dir=ltr><FONT face="Times New Roman" color=#000000 size=3><A href="http://www.movable-type.co.uk/scripts/latlong.html">http://www.movable-type.co.uk/scripts/latlong.html</A></FONT></DIV>
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<DIV dir=ltr><FONT face="Times New Roman" color=#000000 size=3>All those formulas are supported by the field calculator. Perhaps you cannot do all that in one step and need to create several new columns (type DOUBLE) to obtain a final result.</FONT></DIV>
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<DIV dir=ltr><FONT face="Times New Roman" color=#000000 size=3>Of course this can be done also with projected coordinates (in meters) and you'll simply need to compute the euclidean distance.</FONT></DIV>
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<DIV dir=ltr><FONT face="Times New Roman" color=#000000 size=3>Regards,</FONT></DIV>
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<DIV><FONT face="Courier New" size=2><FONT face="Times New Roman" size=3>Juan Lucas Domínguez Rubio<BR></FONT>---</FONT></DIV>
<DIV><FONT face="Courier New" size=2><FONT face="Courier New" size=2><FONT face="Courier New" size=2>Prodevelop SL, Valencia (España)</FONT></DIV>
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<DIV><FONT face="Courier New" size=2>Tlf.: 96.351.06.12 -- Fax: 96.351.09.68<BR></FONT><A href="http://www.prodevelop.es/"><FONT face="Courier New" size=2>http://www.prodevelop.es</FONT></A><BR><FONT face="Courier New" size=2>---</FONT></DIV></FONT></DIV></FONT></DIV>
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<FONT face=Tahoma size=2><B>De:</B> gvsig_internacional-bounces@listserv.gva.es en nombre de Simon Cropper (Botanicus Australia Pty Ltd)<BR><B>Enviado el:</B> mié 02/12/2009 9:48<BR><B>Para:</B> Users and Developers mailing list<BR><B>Asunto:</B> Re: [Gvsig_english] Point2Point Comparison<BR></FONT><BR></DIV>
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<P><FONT size=2>Jorge,<BR><BR>Any idea how I might calculate the euclidean distance using the field<BR>calculator?<BR><BR>The calculator can only interact with one file at a time, how would you<BR>manage two tables?<BR><BR>Cheers Simon<BR><BR>Simon Cropper<BR>Botanicus Australia Pty Ltd<BR>PO Box 160, Sunshine, Victoria 3020.<BR>P: 9311 5822. M: 041 830 3437.<BR>mailto: scropper@botanicusaustralia.com.au<BR><<A href="mailto:scropper@botanicusaustralia.com.au">mailto:scropper@botanicusaustralia.com.au</A>><BR>web: www.botanicusaustralia.com.au <<A href="http://www.botanicusaustralia.com.au/">http://www.botanicusaustralia.com.au</A>><BR><BR><BR><BR>Jorge Gaspar Sanz Salinas wrote:<BR>> On 01/12/09 23:01, Simon Cropper (Botanicus Australia Pty Ltd) wrote:<BR>> <BR>>> Hi Guys,<BR>>><BR>>> Is anyone aware of a utility where you can compare two point layers and<BR>>> get back a table of distances and bearing between each point. I know<BR>>> Sextante can have a file look at itself, so it is possible to merge a<BR>>> file and run this routine but I find that this creates a cumbersome<BR>>> matrix that needs to be disassembled.<BR>>><BR>>> A file with the following fields would be desirable ID_FILE1, ID_FILE2,<BR>>> DISTANCE and BEARING, with one record representing one comparison.<BR>>> <BR>><BR>> Simon,<BR>><BR>> If you have common IDs for the layers, you can do that with a little bit<BR>> of work on the field calculator, extrancting coordinates and calculating<BR>> the euclidean distance (if it's sensible)<BR>><BR>> For a more automated way: Sextante development or some scripting.<BR>><BR>> Nice use case, indeed.<BR>><BR>> Cheers<BR>> Jorge<BR>> _______________________________________________<BR>> Gvsig_internacional mailing list<BR>> Gvsig_internacional@listserv.gva.es<BR>> <A href="http://listserv.gva.es/cgi-bin/mailman/listinfo/gvsig_internacional">http://listserv.gva.es/cgi-bin/mailman/listinfo/gvsig_internacional</A><BR>><BR>><BR>> <BR>_______________________________________________<BR>Gvsig_internacional mailing list<BR>Gvsig_internacional@listserv.gva.es<BR><A href="http://listserv.gva.es/cgi-bin/mailman/listinfo/gvsig_internacional">http://listserv.gva.es/cgi-bin/mailman/listinfo/gvsig_internacional</A><BR></FONT></P></DIV></BODY></HTML>