June 20, 2005
Positional Accuracy Improvement Program
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Susan Smith - Managing Editor

by Susan Smith - Managing Editor
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Welcome to GISWeekly! The use of newer technologies such as GPS for navigation and surveying, orthophotos and satellite imagery have brought inaccuracies in map projections to light. This problem, coupled with the urgent call for a Global Reference System, and the prospect of sharing digital data more widely, have prompted national mapping agencies to seek greater accuracy in map data and products. Read about the Ordnance Survey's Positional Accuracy Improvement Program which is expected to result in increased accuracy for the standard of maps for rural areas in this week's Industry News.

GISWeekly examines select top news each week, picks out worthwhile reading from around the web, and special interest items you might not find elsewhere. This issue will feature Industry News, Acquisitions/Alliances/Agreements, Announcements, Appointments, New Products, Around the Web and Upcoming Events.

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Industry News

Positional Accuracy Improvement Program

By Susan Smith

The use of newer technologies such as GPS for navigation and surveying, orthophotos and satellite imagery have brought inaccuracies in map projections to light. This problem, coupled with the urgent call for a Global Reference System, and the prospect of sharing digital data more widely, have prompted national mapping agencies to seek greater accuracy in map data and products.

Consider the Ordnance Survey of Great Britain, which has implemented a national Positional Accuracy Improvement Program (PAI). That program began in April 2001 and will span five years, with completion expected in 2006. The goal of the program is to allow the Survey to capture Ordnance Survey LandLine (LL) data at 1:2500 scale to a greater absolute accuracy (absolute accuracy is the position of features in relation to the Ordnance Survey National Grid), which will result in increased accuracy for the standard of maps for rural areas. In addition the Program will ensure the data for the addition of new building development and other change, as well as resolving inconsistencies between
Ordnance Survey 1:2500 scale map data and customers' own GPS data.

The result of this program is that some 1:2500 LL data (both rural towns and rural areas) has been moved or transformed which means that data that has been captured against it will now be out of alignment. The PAI will affect anyone currently using LandLine or the MasterMap dataset, and users and managers will need to plan how to manage the problem. In an article in GI News, January/February 2003, entitled
Positional Accuracy Improvement - what it means and what to do, authors Tom Timms, Giles D'Souza and Rajesh Kalra outline some of the challenges of PAI and what the possible methods might be to deal with the problem. Their solutions include re-capturing all data, using link files to perform an automated transformation, or implementing a hybrid solution: transform users' data automatically using the link files and then to post-process the data (in automatic and manual ways) to resolve any residual problems.

A number of consultants and software vendors offer products to automate the process according to specific agency needs. Sometimes, due to the number of technology platforms being used in concert, a combination of technology and manual processes are suggested for automating the process.

The creation of the PAI Toolbox is an additional structure to navigate the Ordnance Survey positional accuracy improvement (PAI) website and find out what organizations who need to implement PAI for their dataset need to do next. It complements the Ordnance Survey PAI website.

ESRI (UK) have a developed a set of tools to specifically help you shift your data.

The new ArcGIS extension for ArcGIS Desktop 8.2 and above performs two functions:

- Load the link files supplied by OS

- Shift selected features

For more details about the ESRI (UK) PAI Tools visit the
download a copy of the tools.

Warp is designed to realign customer's data to match the newly surveyed OS data.

Apic Ltd. Has developed APIC-Shift, a software solution to transform users' data using link files.

RMSI has developed a multi-user system for positional accuracy improvement of data in the United States and is developing these methods on sample datasets with Landmark in the UK.
Infotech also offers products, solutions and consulting for shifting data for the PAI program.

The Ordnance Survey in Britain has extended its PAI program so that the Rural Town Programme is now complete, including 210 towns. Land-Line customers received processing and link file creation in the December release and this release was made available as part of OS MasterMap at the end of January 2005.

Plans are to complete the entire PAI program by March 2006. So much of the progress of the PAI depends upon seasonal and weather considerations for flying.

Now that the program is in full production and vendors are ready to offer help with shifting data and resolving inconsistencies, it is becoming apparent to other national mapping agencies in other countries that a PAI can be greatly beneficial in providing an accurate digital map base for use as a foundation for future GIS technologies.


NVision Solutions, a provider of mission-critical, GIS-based decision support systems, and FirstCall Network Inc., an emergency notification services company, entered into a strategic agreement to create an integrated solution for the emergency management and homeland security industries.

Laser-Scan announced a new partnership with Australian-based Open Spatial. This new agreement establishes Open Spatial as a Master Reseller for Australia and New Zealand and enables them to resell Laser-Scan's 'Radius Topology'.

The alliance has grown from the demand for Oracle-based spatial applications in the Australasian marketplace. Open Spatial are geospatial solution integrators for the utility and local government marketplace and deliver purpose built applications that have proven productivity and efficiency improvements. Laser-Scan's Radius Topology will now become an essential part of their offering.


Ordnance Survey and its business partners are celebrating the success of a major conference designed to champion the growing use of geographic intelligence in business. Around 140 representatives of Ordnance Survey partners, publishers and developers attended the two-day event at the Alexandra House conference centre near Swindon.

More information is available at

NAVTEQ, provider of digital map data for vehicle navigation and location-based solutions, reports 2004 as a year of significant growth for the navigation industry in North America with the introduction of navigation as a new option on 29 North American car models. The adoption rate of navigation, or the total number of vehicles offering navigation as a standard or optional feature based on the total number of available vehicles, grew significantly in North America, reaching 37% of vehicles sold in 2004. With the addition of these models, a total of 79% of North American automotive brands offered navigation in 2004.

A digital mapping facility on the Big Roman Dig* site is being provided by geographic information systems (GIS) provider ESRI (UK), using data from Great Britain's national mapping agency, Ordnance Survey. It enables viewers to explore TV featured sites, Roman finds and identify the nearest 'dig' activity in which they can participate.

Big Roman Dig, which will be broadcast from 2 to 9 July, will see Channel 4's Time Team explore not just one Roman fort, villa or even city, but undertake projects covering the whole country.

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