Articles & Case Studies

Spatial data applications from InfoWorks WS models

Posted: Thursday 10th December 2009

One of the major challenges faced by water network modelers is the presentation of results to those not directly involved in the modeling process. Modelers are often extremely involved at a very technical level, but it is often challenging for them to translate their ideas and findings into a format for distribution to system operators or managers.

Modelers are used to reporting the results of their studies using traditional, paper-based methods, but such documents can be hard to understand and very difficult to present as they often contain insufficient graphics and dynamic content. There is sometimes a need to translate what is typically seen on an InfoWorks WS screen in order to present it to a board of directors who are providing funding for schemes.

Case studies

Portsmouth Water is a water-only company in Hampshire, on the south coast of the UK. It supplies a population of 662,000 and covers a supply area of 868 square km. Portsmouth Water does not have an in-house modeling capability but is nonetheless progressive in its approach to new technology and fully recognises the positive impact that modelling software such as InfoWorks WS, can have within the company.

Portsmouth Water’s strategy has initially been set to commission models to resolve specific current issues, rather than building models area by area. It requires outputs from the models in a format that can be easily understood and simply distributed. To reach that stage it was necessary for Portsmouth, UK based water engineering consultancy, HydroCo, to overcome some obstacles including a GIS system that had not been designed to cater for the data requirements of modeling.

The required model covered 725km of mains pipes and around 107,000 customers. The main challenge was that data had been entered into the GIS as a schematic representation; a pipe run would be shown with a gap where it crossed another pipe as a device to visually represent the fact that these were separate pipes. This caused considerable problems when trying to import this data into the network model because the model could not cope with the pipes shown as disconnected.

To resolve this, the existing GIS system data was analysed, searching for end caps, hydrants, washouts, checking the ends of pipes and other unclassified pipes and end nodes.

Node identification

Next the eligible nodes identified as being of the same diameter, material and age were examined, to enable identification of pipe joins. After this, it was possible to join all of the pipes with few errors.

Once the data issues had been resolved and the model built and calibrated following a field verification exercise, it was proposed that Google Earth may provide a viable presentation option. Google Earth is a rich 3D spatial environment, provided at a low cost and an excellent platform for evaluating spatial data. It is relatively easy to build a file and import any spatial data straight into the application using the proprietary kml format.

HydroCo was aware that it was possible to export directly from InfoWorks into Google Earth, which enabled a trial to evaluate its usefulness. An existing model was exported to prove the concept. Features include the ability to click on nodes to obtain additional information, and the solution enables a view of the model in a 3D environment.

It became obvious from the trials that .kml or .kmz files exported from InfoWorks could be quite large, and all of the model based attributes were being populated, many of which were not relevant. It was therefore decided to undertake some simplification work to the files themselves.

At this stage the idea of using building heights in Google Earth to visually represent available levels of service pressure for tall buildings, was also investigated. Google Earth provided the facility to define building heights and form a three-dimensional shape or building, allowing the possibility of inputting live building heights into the network.

Blue Sky thinking

To obtain that information, HydroCo contacted one of Google’s data partners, Blue Sky, which can provide a number of datasets to assist in the production of digital elevation models for modelling purposes, including the familiar Digital Terrain Models (DTMs), which have been used in InfoWorks WS for many years and give ground levels within an area – a useful tool for calculating network pressures. The company also offers Digital Surface Models (DSMs), a less well-known type of dataset that gives the height of the buildings on a surface.

Taking an existing InfoWorks WS model, the data was exported in .csv format and then converted into longitude and latitude as required by Google Earth. Building polygons were also created, with Ordnance Survey data used to create a polygon layer. Building heights were then assigned using the new DSM dataset from Blue Sky and exported in a .kml format or its compressed alternative, the .kmz file.

There was a choice of two datasets, both of the geoperspective DSM type. The standard version was chosen, accurate to +/-1.5m.To assign heights to buildings, a solution was developed that assessed all of the points on the grid which were contained within the building outlines. A statistical calculation was then employed to determine a single representative height for each building.

The resulting output in Google Earth gave a very visual representation of the network and nodes, relative differences in height and additional data the company was considering importing, such as properties that had been successfully linked to the billing database. Buildings could be colored to represent different themes as required.

PortsmouthCityCentre

HydroCo was satisfied with the result, and undertook a second trial focusing on Portsmouth city centre.

The value of this approach is that it enables modelers to fulfil the difficult task of explaining their modeling outputs to non-modelers. In terms of pressure, such a representation also facilitates a good understanding of flood contours, which can also be obtained in FloodWorks.

For pressure management, the height data can be examined and the head contour lowered at a particular location to discover the service level issues that would arise. This approach can also be used to tune the system for pressure reduction at night. As the head contour is reduced, the affected properties are identified, and moving the view around within Google Earth allows identification of those properties that would be affected first.

One of Portsmouth Water’s concerns was for the city’s high-rise buildings.

Although generally high rise building are supplied from ground level storage and high rise boosters , one of PWC concerns are properties at an intermediate ground level that historically have relied on mains pressure as a form of supply. Traditionally, pressure is measured at ground level, and reported at a node, but the utility needed to ensure that there was sufficient pressure at the top of a high-rise building supplied directly from the main.

Sharing Information

Uploading the information onto the internet allows modeling information to be distributed in a non technical format to a wider range of clients outside the direct environment of modeling. HydroCo has developed HydroView, a working system that can upload InfoWorks models to a web server and distribute them securely to a number of web-based clients.

The consultancy has embedded Google Earth views within this application, allowing these to be viewed without the complexity of the Google Earth interface or its intensive bandwidth restrictions. The system provides a useful means for operators to view their infrastructure, reservoirs and buildings and also generate graphs of flow and pressure in a very easy to use format.

WessexWater models

HydroCo has also worked with Wessex Water, and has built a number of models for the utility, including one of Salisbury and the coastal Poole area. The projects involved model building and calibration phases but there was also an additional requirement to undertake a pressure management study to identify the scope for pressure reduction and identify average zone night pressure locations. The results from this analysis would be used by leakage teams optimise pressures throughout the distribution system during the day.

To achieve this, HydroCo developed an application to import InfoWorks WS model networks with key information populated in the User Text fields. The results from the model run were pasted back into the InfoWorks User text fields. This enabled the all of the relevant data both network and results to be contained within one .CSV file. It was then possible to pull this information into the application and use it to determine the average zone night pressure (AZNP) positions, the critical customers within the zone and to trace suitable logging points to verify those locations in the field. Ultimately, the solution automatically generated a .pdf file that presented this data spatially zone by zone for those implementing the leakage programme.

Summary

There are separate and distinct challenges in modelling technology and presenting the results of modeling exercises. An excellent modeling tool has been created in InfoWorks WS, but it is also necessary to consider how to convey that information to project sponsors and how to use the outputs from the projects in a format which is both accessable easy to understand. Google Earth has proved a useful presentational tool, and there will be additional developments in InfoWorks WS to further utilize the solution’s functions in the future.

Because of InfoWorks WS’s flexible inputs and outputs it is very easy to manipulate data into the correct formats for interfacing with bespoke applications or other proprietary presentation tools.. If ideas can be presented more visually, modelers are able to increase their chances of engaging more effectively with system operators and company management.

This article is based on a paper presented at theWallingfordSoftware International User Conference in September 2008 by Robin Armstrong of HydroCo.




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