Section: 4.5.2 ximg File Format

4.5.2 ximg File Format

Image XML Files The Image Xml file format (.ximg) allows one to define collections of geolocated images (and also shapefiles). The simplest file can define one geolocated image:

  <image url="sboulder.jpeg"
       name="South Boulder-aerial photo"
       ullat="39.98890" ullon="-105.22782"
       lrlat="39.98755" lrlon="-105.22548"/>

The url attribute can be an absolute or relative url or file path. The ullat, ullon, lrlat and lrlon attributes are the upper left and lower right lat/lon of the image. It is assumed that the image is in a geographic (i.e., rectilinear, lat/lon) projection.

Collections

You can also define a collection of images:

<collection name="Boulder Images">
  <image url="sboulder.jpeg"
       name="South Boulder-aerial photo"
       ullat="39.98890" ullon="-105.22782"
       lrlat="39.98755" lrlon="-105.22548"/>

  <image url="bouldertopo.jpeg"
       ullat="40.06654" ullon="-105.34710"
       lrlat="39.98040" lrlon="-105.19676"
       name="Boulder topo"/>

  <image url="bigtopo.jpeg"
       ullat="40.22807" ullon="-106.66437"
       lrlat="39.54718" lrlon="-105.45623"
       name="Mountains topo"/>
</collection>

Collections can contain other collections:

<collection name="My Images">
    <collection name="Madison Images">
        <image url="madison_aerial.jpeg"
              ullat="43.09444" ullon="-89.52626"
              lrlat="43.01143" lrlon="-89.36579"
              name="Madison aerial"/>

        <image url="madison_topo.jpeg"
               ullat="43.09444" ullon="-89.52626"
               lrlat="43.01143" lrlon="-89.36579"
               name="Madison topo"/>
    </collection>
    <collection name="Boulder Images">
       <image url="sboulder.jpeg"
              name="South Boulder-aerial photo"
              ullat="39.98890" ullon="-105.22782"
              lrlat="39.98755" lrlon="-105.22548"/>
     </collection>
</collection>

There is also a shape tag for defining shape files:

<collection name="Shapes">
   <shape url="boulder_roads.zip" name="Boulder roads"/>
   <shape url="boulder_rivers.zip" name="Boulder rivers"/>
</collection>

Grouping

The group tag allows you to group a set of images in time or space:

<group name="group of images"
       format="yyyyMMddhhmm"
       ullat="39.991856"
       ullon="-105.226944"
       lrlat="39.989426"
       lrlon="-105.222656">
       <image
           date="200610011000"
           url="sketch.jpg"/>
       <image
           url="map.jpg"
           date="200610011100"/>
</group>

The format attribute defines the date/time format of the date attributes. The location attributes (ullat,ullon, etc.) can be defined both in the group tag as well as in each individual image tag.

If there are no date attributes then the group of images are aggregated together, each potentially covering a different area.

Images in 3D Space

One is not limited to just specifying the positions of the upper left and lower right corners of the image. There is support for defining the latitude and longitude for any of the four corners of the image:

  <image url="image.jpeg"
       name="Image"
       ullat="40" ullon="-100"
       lllat="30" lllon="-100"
       urlat="50" urlon="-90"
       lrlat="30" lrlon="-90"
      />

One can also specify the altitude of any of the points. The unit specification is not required and will default to meters.

  <image url="image.jpeg"
       name="Image"
       ullat="40" ullon="-100" ulalt="20000[feet]"
       lllat="30" lllon="-100" llalt="0[feet]"
       urlat="50" urlon="-90"  uralt="5000[feet]"
       lrlat="30" lrlon="-90"  lralt="0[feet]"
      />

The IDV will try to fill in defaults. So, for example, if you wanted to have an image be a vertical cross section you could do:

  <image url="topo.jpg"
       name="Image"
       ullat="40" ullon="-100" 
       urlat="50" urlon="-90"  
       ulalt="20000[feet]"    
       llalt="0[feet]"/>

Here, we define the lat/lon of the upper left and upper right of the image. We define the altitude of the upper left and lower left corners of the image. The altitude of the upper right corner defaults to that of the upper left and the altitude of the lower right defaults to the lower left altitude.

Unidata IDV Workshop for version 6.3 > Advanced Topics > Miscellaneous Items