The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008
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based on LPS technology. ERDAS ortho tools are launched
automatically within LOA. Ortho CuePac uses GeoCue to
define production steps. Various orthorectification parameters
can be defined as a part of the workflow. Distributed processing
is also an important aspect of Ortho CuePac. Users can run
large orthorectification jobs on different machines in order to
reduce overall processing time. Orthorectification jobs can be
submitted from different machines. LOA sorts them in a queue,
allows users to choose which machine and when to run jobs.
Ortho jobs can be scheduled at a later time. Data locking
mechanism prevents data collisions in a multi-user environment.
On client machines users can see the real-time status updated of
the submitted ortho jobs. Users are informed when the jobs are
completed.
Mosaic CuePac is a GeoCue environment that integrates
ERDAS MosaicPro into the GeoCue geospatial process
management framework. LOA launches ERDAS MosaicPro as
an external process to generate seam lines, perform color
adjustment and decide on parameters as feathering and
smoothing options. ERDAS MosaicPro improves the seam
editing portion of mosaicing as well as offering additional
radiometric adjustment capabilities. Figure 1 shows orthophotos
generated on LOA.
used full SQL server should be installed. In this setup, the
server is running with MSDE.
In this experiment, a Pentium 4, 2.40 GHz with 1.00 GB of
RAM running Windows XP is used as the Server machine.
During the performance analysis no jobs has been run on
GeoCue server.
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Figure 1: An LOA project showing ortho images of Hessen,
Germany. DOP, (c) HVBG 2007
2. SYSTEM SETUP
2.1 System Requirements
In this experiment, the LOA system setup consists of a Server
machine, a client machine and 5 ortho rectification nodes
The GeoCue Server is the heart of the system providing the
central control and management functions. This is the most
important machine, which matches jobs with selected machines.
GeoCue uses a database for storage of project metadata (data
about data), project data and the configuration information that
defines a workflow environment. High density data such as
image and elevation data are stored in flat files in distributed
data storage within the network connected file system. GeoCue
maintains references to these externally stored data.
GeoCue Server can run with MSDE or with full SQL Server
installation. MSDE limitation is 5 nodes. If more nodes will be
Figure 2. System Components
The GeoCue Client is the machine that submits ortho or
mosaic jobs to the nodes. The project status may also be tracked
on these machines. Client machines are the production
workstations. There should be only one Client Machine per
human operator dedicated to LOA. Depending on the
production needs several Client machines can be used
simultaneously. The GeoCue Client is a window into the project
while the data processing is performed on the ortho nodes. In
this study one workstation is used as the Client machine. The
ortho jobs have been submitted using client machine.
In this experiment the GeoCue Server and the Client are the
same machine.
Ortho Nodes are the workers that perform the computation.
Ortho nodes can be any system on the network. They can be
installed on a production machine not in use or a dedicated
node in a server room. However, ortho nodes are recommended
to be dedicated to ortho processing only whereas on client
machines operators can run alternative processes.
Ortho nodes do not have a user interface, but they report
feedback and success or failure information back to the client
machine. The number of the ortho nodes is highly scaleable
depending on the production needs.
In this experiment, system setup consists of 5 ortho nodes. Each
node has the same specification: Pentium 4, 3.20 GHz with 2.00
GB of RAM running Windows XP. No other jobs were run
during the performance experiment on ortho nodes.
Networking: Network is the connection between the GeoCue
Server, client worksations, ortho nodes and the data storage
locations. The installation is done on a network domain. The
machines are connected in a local area network. Interconnection
between the nodes, client machine and the file server was done
using gigabit Ethernet. Gigabit bandwidth refers the data rate
supported by the network connection. The performance will be
greater when larger bandwidth is used. However, bandwidth is
not the only factor that affects the speed. Network traffic might
cause latency in the transmission. Also addition of the too many