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