The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008
nodes might reach the point of diminishing returns.
This experiment was not done in a dedicated network, therefore
some network traffic and bottlenecks due to I/O has been
examined and reported in the result summary.
2.2 LOA Setup
The work required to install LOA is minimal and IT expertise is
not required. The user needs to select the Server machine that
will host GeoCue Server application, the workstations that will
host GeoCue Client application and ortho nodes that will run
the jobs. The following steps explain how to setup LOA.
• Install GeoCue Server software on the server machine.
• Install MSDE if Server machine is not running with
full SQL Server.
• Run database manager and install GeoCue database
• Select Common Folder and share it
• Decide data storage locations (GeoCue WareHouse)
and share them
• Import Licenses
• Install LPS and GeoCue Coordinate systems
• Install GeoCue Client software on the production
workstations and ortho nodes and configure it.
• Install LOA on Client workstations and ortho nodes
• Install LPS support modules
LPS
SOCET SET
MATCH-AT
I SAT
1
Import a
photogrammetric
project
I
I
Import
elevation
t
IMG
LTF
Ortho CuePac
Link DTM
to Ortho
Layer
1
Figure 3. Ortho CuePac workflow chart
3. ORTHORECTIFICATION WORKFLOW IN LOA 4. PRACTICAL RESULTS
LOA workflow starts with setting up a project. Then a
photogrammetric project (e.g. LPS block file) is imported into
GeoCue. The photogrammetric project should be a triangulated
block. The next step is to generate rectification entity. In this
step ortho layer will be generated and rectification parameters
such as output pixel size, resampling method, projection
information will be defined. An elevation file then be imported
and linked to ortho layer. Multiple elevation files can be
imported. The linking step will establish the elevation files to
be used for rectifying each image. Validating elevations will
update the footprint of the ortho entities by intersecting ortho
entities with the linked elevation files. This step will invoke the
dispatch dialog. Validate elevations step can be on several
nodes.
Once the validate elevation step has been completed, the next
step is orthorectification. On dispatch dialog, the user can select
the machines to run orthorectifaction jobs. The status of the jobs
can be tracked on dispatch monitor. The dispatch monitor
displays jobs that are pending, in progress and completed. Once
the rectification is finished on any of the nodes the raster
images will be displayed on the map view. A typical distributed
run is shown in Figure 6.
For this experiment, two triangulated blocks with 240 and 858
frame images have been selected to show the timesavings as a
result of using the distributed processing in LOA. For further
referencing, these blocks will be referred to as Block 240 and
Block 858 respectively.
Source Images
Both blocks contain TIFF format 8 bit frame images and they
are 962 MB each. File caching was enabled during these tests.
The source images were stored in the file server and then copied
to each node’s caching folder to perform orthorectification.
Once orthorectification is complete, the ortho images were then
transferred to the GeoCue WareHouse on the file server.
DTM used in Orthorectification
The DTM was physically loaded onto each workstation for each
orthorectification process. The DTM is copied from the server
to the local hard drive of the node each time an image is
orthorectified. The 10m cell size DTM is 27 MB in size. This
means that in addition to the source images, 27 MB of DTM is
also copied from the server to each node’s caching folder.
Table 1 summarizes the characteristic of the project.
Block 240
Block 858
Capture GSD (m)
0.11
0.11
Output GSD (m)
0.15
0.15
Forward Overlap (%)
60
60
Source Data Size (GB)
226
806
Project Area (knYl 2 )
91
735
Table 1: DataSet Summary
