[Liblas-devel] Creating LAS file, header coordinates doesn't set (Carlos Piury)

[Michael Rosen]

You can change the header after you write points.  The Writers have an "update_header" call for this purpose.

Here's how we use it:
...
   if(m_writer != NULL)
   {
      if(!failed)
      {
         m_header->number_of_point_records = m_lasinventory->number_of_point_records;
         for (int i = 0; i < 5; i++) 
            m_header->number_of_points_by_return[i] = m_lasinventory->number_of_points_by_return[i + 1];
         m_header->max_x = m_header->get_x(m_lasinventory->max_X);
         m_header->min_x = m_header->get_x(m_lasinventory->min_X);
         m_header->max_y = m_header->get_y(m_lasinventory->max_Y);
         m_header->min_y = m_header->get_y(m_lasinventory->min_Y);
         m_header->max_z = m_header->get_z(m_lasinventory->max_Z);
         m_header->min_z = m_header->get_z(m_lasinventory->min_Z);

         if (! m_writer->update_header(m_header, FALSE, TRUE))
            THROW_LIBRARY_ERROR((LTL_STATUS_FORMATS_LIBLAS_WRITER))
            ("Unable to update header");
      }
      m_writer->close();

...

-----Original Message-----
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Sent: Thursday, January 08, 2015 12:00 PM
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Subject: Liblas-devel Digest, Vol 72, Issue 1

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Today's Topics:

   1. Creating LAS file, header coordinates doesn't set (Carlos Piury)


----------------------------------------------------------------------

Message: 1
Date: Thu, 8 Jan 2015 13:09:55 +0100
From: Carlos Piury <dgpiury at gmail.com>
To: liblas-devel at lists.osgeo.org
Subject: [Liblas-devel] Creating LAS file, header coordinates doesn't
	set
Message-ID:
	<CAHMfM_d0ZxumM1eaA3E9FR6a0Q4hwxZXQjMffKvOv0gPUDk0-Q at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

Hi, I am trying to create a LAS file using the c++ API following the tutorial posted in the web page for c++. But when I use "lasinfo" tool for check the result I see the header "MAX X Y Z" and "MIN X Y Z" attribute with value "0" instead of the values with the point that I wrote.

## My code:

main()
{
......
      liblas::Header header;
      liblas::Writer writer(ofs, header);
      liblas::Point point(&header);
      point.SetCoordinates(10, 20, 30);
      writer.WritePoint(point);

      return 0;
}
.....

## Lasinfo Output:

---------------------------------------------------------
  Header Summary
---------------------------------------------------------
...
  Min X Y Z:                   0 0 0
  Max X Y Z:                  0 0 0
...

  Minimum and Maximum Attributes (min,max)
---------------------------------------------------------
  Min X, Y, Z:         10, 20, 30
  Max X, Y, Z:         10, 20, 30
...

I think (reading the lasinfo code) that lasinfo implementation uses an structure "Summary" and add each point readed to that structure, for this reason the values are right in the second output ("Minimum and Maximum attributes (min,max))". However I don't know if it's possible modify the header after a point is inserted, I tried it unsuccessfully :(.

Someone knows how to modify the header after the "liblas::Writer writer(ofs, header);" call or if the writer implementation must fix the header max and min?

Thanks ;).
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