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Enterprise Integration
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Geospatial technologies integration / management
Technologies integration
The technologies that will be discussed emphasize their use for better integration and cost
effectiveness when used to develop GIS applications. These technologies can be grouped in the
areas of data capture (photogrammetry, remote sensing, GPS, CAD, SCADA, and EDMS),
database design and implementation, and communications (local, remote, mobile, Internet),
- Data Capture Technologies
- Aerial Photogrammetry: From the different classes of photogrammetry we are interested
in aerial photogrammetry, used to develop pkmimetric detail and topographic configurations.
Several steps are involved in the generation of digital maps that we need to be aware of such as
acquisition of aerial photography, field control surveys, digital data collection, aerotriangulation,
photographic reproduction, orthophoto and feature capture field survey.
The project manager has to decide how to use the technology after evaluating the requirements of
the application. The main points to consider are the positional accuracy, the boundary for that
accuracy, the pixel resolution and deliverables needed.
The combination of these requirements will impact directly the cost of the project.
For example, if we are dealing with a pipeline project, we don't need to provide the same
accuracy to all the project. A greater level of accuracy can be provided for areas closer to the
pipeline and lesser accuracy to the rest. The flight altitude will be the primary determinant of the
accuracy, and will determine the ground area covered by each photo the number of photo / stereomodels
and the density of ground control, issues that will impact the cost directly. Then the
determination of the project boundaries with different levels of accuracy is very important.
Another issue is the pixel resolution. Use the resolution that you need depending on the features
that you need to identify. Don't go beyond that. Also consider other alternatives to capture
some of the features that will help you going to a lower resolution. The pixel size will impact
directly the size of the files where size= (length x resolution) x (width x resolution) x 1 byte/dot
for an 8-bit gray-shade .TIF file. And for color the size will be triple. Now using algorithms we
can compact the file sizes but still it is and issue that we need to deal with when we manipulate
those files, specially if they need to be used in a network environment. Some schemes such as an
image pyramid where different levels of resolution can be used to see an area depending on the
level of zooming can be used. The farther you are when covering a big area the biggest size of
pixels you will use diminishing the file size and manipulation time.
- Remote Sensing: Multiple applications can be developed using this technology. GIS
Environmental mapping, crop monitoring, Digital terrain modeling (DTM), and emergency
response are a few samples of its use. For Engineering applications and mapping of large areas
where aerial photography could be expensive or not available, remote sensing is a very good
alternative.
The generation of contour line maps from the DTM's, that in the case of the Systeme Pour
l'Observation de la Terre (SPOT) imagery can give us a vertical accuracy of 7 to 12 meters, is
used to detect the best alternatives to lay a pipeline or construct a road. These contours are also
used for siting and system design of cellular communications systems, and for prevention and
evaluation of floods and inundation caused by tsunamis.
Factors that we need to consider when using this technology in addition to accuracy and
resolution previously discussed are:
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The acquisition of the appropriate imagery that can be from multispectral scans, thermal
scans, radar imagery or a combination from different sources of satellites such as LANDSAT, the
IRS-1 A and IRS-2A from the National Remote Sensing Agency of India, SPOT, the National
Oceanic and Atmospheric Agency (NOAA) and 2 meter resolution panchromatic SPIN-2
Russian satellite image data.
- Availability of imagery will depend on the coverage, revisit, sensor types, library available
and age of the images.
The combination of types of data is also important, for example for an emergency response
application for a country we can use LANSAT data to cover general areas and we can use SPOT
data for the city areas were the bigger losses will be. The usage of older data is also important, it
can be used to generate a DTM because the topography doesn't change that much and four year
old data will be half the price of newer data.
- Global Positioning Systems (GPS): The usage of this technology as I mentioned in the
introduction is very valuable for GIS applications. It can be used as a surveying tool, providing
very accurate positioning and measures to establish the base map for engineering type of
applications or to collect GIS attribute data for the features. This capability is the more
important integration issue between GIS and GPS technologies, because we can efficiently
collect and simultaneously position attribute data with the GPS data collectors.
GPS has changed the way topographic and planimetric data is collected. The integration of GPS
with other data capture technologies, such as laser and cameras, allows us to perform airborne
laser mapping integrated with differential kinematic GPS with much lesser ground control.
This has an advantage over previous methodologies, when collecting data for difficult access or
remote located GIS projects.
In both cases when we used GPS to collect accurate surveying data for our base map or attribute
data for the features in the GIS applications, the main concern is planning which information
needs to be collected. For example if we are collecting surveying information for our base maps
to get a better location of our pipelines, we don't need to collect all the points of the pipeline. A
combination of office and field work will give the best results in time and money. The key
element is to select in advance which are the points that need to be collected in the field. This
planning can save time and thousands of dollars.
- Computer-Aided Drafting (CAD): Is used for editing and presentation of graphic
information on computer-drawn maps or drawings. I am including CAD as part of the data
capture technologies from the point of view of GIS because it is the main tool that allows us to
enter vector data into the system. To better understand the integration of CAD with GIS, I will
clarifi the use of the spatial data elements by each technology which are: Value(Database),
Shape(Graphics), Location(Coordinates, Map Projection and Datum), Topology (Connectivity,
Orientation, Adjacency, Containment).
The spatial elements that CAD mainly uses are Graphics (Points, Lines, Areas, Symbols and
Text), Coordinates and orientation. Topology is not used by CAD and Map projections are not
of primary importance. Those two spatial elements are used by GIS. Then, if we consider that
CAD will be feeding GIS with graphic and vector data we just need to see how this data is used
by GIS to allow an easy integration between technologies.
Because GIS uses topology and the main data elements used by GIS are (points, lines and
polygons), one important task where CAD will ease the integration, is providing clean data
needed by GIS to generate topology and allow spatial analysis, queries, routing, etc. Generation
of CAD data elements must include:
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Closed polygons using precision placement where the last coordinate pair of a digitized area
boundary must exactly match the first pair and all area boundaries that represent different
features should reside on different levels whenever possible.
- Common line segments shared between graphical features should have only one line that
represents the common segment.
- Linear features should be created using a continuous line string and when they intersect with
other linear feature of the same type, level and symbology must be terminated at the point of
intersection.
- Provide a list of the GIS items that will be used in the map and the levels to reside.
Another important issue is the location of maps by using a predetermined coordinate system.
There are more issues that need to be considered to assure a smooth integration of CAD and GIS
to increase productivity and save time and money. My recommendation will be to implement
inside the normal CAD standards used by the drafters the minimum additional standards needed
to allow us to have CAD/GIS ready digital maps.
By using these standards, you can alleviate the conversion process. In a study conducted in
MWD implementing the GIS standards for the right of way maps mean an additional work of
three hours per map versus ten to thirty four hours of conversion time per map needed in the
future.
- Supervisory Control and Data Acquisition (SCADA): SCADA can provide to GIS with
data on current system status and also it is a source of historical data of systems operations. It is
important to clarify that the type of information collected by SCADA is sequential in time for
each point in the network, and it generates large amounts of information. In the case of GIS, we
represent the information graphically for all the network at a certain point in time. Then the
information that will be extracted from SCADA to be used in GIS will be more of an historic
type, for example what were the pressure peaks in the network yesterday, or two hours ago. An
online system is feasible, but more difficult to implement. By other side, GIS gives SCADA the
graphic and spatial component and ability to perform spatial queries to the Operations area users.
For example, if there is a problem reported by the public, that normally will provide street
intersections or addresses to identify the location, then Operations by using GIS will be able to
locate easily which segment of the pipeline corresponds to that intersection area and take the
corresponding response measure.
- Electronic Document Management System (EDMS): The need to access documents in a
variety of formats from GIS is increasing because 70°/0 of all information used today has a
geographic element and GIS provides the environment to do it. By integrating both
technologies, a GIS user will be able to perform queries or access documents related to a
geographic location which can be slides, digitized video and audio, scanned (raster) drawings and
paper documents, and other digital documents.
To allow the integration of GIS and EDMS our first task is to identify which are the documents
that we are interested in to retrieving using the geographic component, how we will provide this
identification to the documents, and how this geographic identifier will be included in the
database. This identifier will be use when performing geographic queries, such as to retrieve
documents contained in an area. An alternative can be to have a pseudo geographic search by
linking our documents in the database to other features that cover our entire area to use their
geographic component.
The next step after the definition of the geographic identifier is to create the interface to
communicate between the GIS and EDMS because EDMS normally has their own proprietary
algorithms to save and access data. Also, when we came from the EDMS side and a user needs
information with a geographic component like what documents can be related to a street
intersection, we will need to send the query to GIS.
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