MultiVision. an indispensable tool for analysing oblique imagery

Transcription

1 MultiVision an indispensable tool for analysing oblique imagery

2 Oblique Aerial Imagery For as long as most people can remember there has been oblique aerial photography, flown speculatively for the most part by the early pioneers of aerial survey. Often sold by students to householders in the long summer vacations, the original Aerofilms library of oblique imagery has been consigned to history and is now owned by English Heritage. As mapping and photography became digital, the requirement for obliques seemed to fade away. Today however thanks to new software, image capture techniques and equipment there is a revival in the demand for oblique imagery. Based on sound photogrammetric techniques new software has been developed to provide a new environment for viewing the world from the air. MultiVision, is a unique product that combines vertical aerial photography with oblique photography in a single software environment. With MultiVision the centre of the screen is taken up by a vertical aerial photograph, a mouse click on any point in this image prompts the software to display 4 oblique photos taken from multiple directions, normally N, S, E and W. These multiple perspective views look inwards towards the chosen point in the vertical image making it really easy to understand what is being viewed on the ground whilst providing lots of additional information that a vertical image alone cannot deliver. MultiVision comes complete with a set of built-in tools which enable accurate measurements to be taken eliminating the need for a site visit in many cases. The measurements can be taken direct from the oblique photography using the tools provided, making it possible to ascertain building heights and elevation areas, calculate distances and much more. MultiVision can also work seamlessly with a GIS system so a user might be looking at maps or imagery within Map Info for example and switch backwards and forwards between the two software environments as the need arises. For MultiVision to work effectively 3 datasets are required. Firstly a vertical aerial survey, something that most Local Authorities already have. Secondly a digital elevation model, those Local Authorities who have taken NEXTMap Britain data under the MSA, will already have this. This provides the essential xyz 3D geometry that enables MultiVision to combine the vertical and oblique photography. Thirdly the oblique aerial photography. To take advantage of the unique MultiVision environment, Getmapping in partnership with Bath Spa University has pioneered a unique rotating digital camera called the Azicam. The Azicam takes a radical approach to oblique image capture. Instead of a normal four camera array used to take North, South, East and West (90 ) orientations the Azicam is a single medium format camera mounted on a rotating plate or spinner driven by a precise friction motor to orient the camera for each shot. Navigational and recording GPS ensures accurate geo-location. The Azicam system has several advantages. Using a single higher resolution camera delivers a wider area of coverage, better image quality and costs less to calibrate and maintain. The whole system will fit in an aircraft already configured for a single vertical camera installation. Finally this method of oblique image capture is very cost-effective. The Azicam in situ in the survey aircraft. NB: The Azicam uses the same aperture in the aircraft as a normal vertical image camera

3 MultiVision an indispensable tool There are a number Local Authorities now using oblique imagery captured by Getmapping along with MultiVision software. It is proving indispensable. Surrey Heath Borough Council At Surrey Heath Borough Council MultiVision has been in use for two years and there are over 30 staff using it on a daily basis. The range of uses has expanded over time but it is now well embedded within a number of departments. One of the first users was the Tree Preservation Service. The software is used to assess the amenity value of trees not currently protected, to check on protected trees and also to provide evidence for prosecution. Being able to measure the height of a tree and see exactly in which property it resides is particularly helpful. It is also used for high hedge measurements in the case of disputes and to inform the planning process where trees are concerned. Rates personnel concerned with collection of Council Tax and NNDR are also avid users of MultiVision. It is largely used for building assessment, to check the number of floors in multi-tenancy buildings, for empty property relief, single person discounts etc. It can also be used for curtilage analysis, to check unknown business assessments, rating property extensions and for assisting the Valuation Office. The Planning department is another major user of MultiVision. Very quickly it has become the preferred tool for pre-site assessment. Access to properties can be determined and measurements taken prior to a visit taking place, so maximising the use of time spent on site. Increasingly MultiVision is used to spot illegal developments and to check compliance with planning permission. Imagery can be captured and pasted into reports and measurements taken to support appeal hearings. Because MultiVision enables five different views it provides an easy way to assess line of site and separation distances. It is easy to export images from MultiVision and these can then be overlaid with a council s own labelled GIS data. At Surrey Heath this is being used by senior managers to assess redevelopment. Parking enforcement personnel are also using MultiVision to precisely locate incidents. These can then be referred to Highways for confirmation of queries such as road adoption. MultiVision is also used to inform and determine planning policy. It is a good tool for open space analysis to determine development potential and is being used for urban design appraisal providing building heights, plot widths and details of landscape features which would be more difficult to interpret from vertical imagery alone. In conservation areas MultiVision makes it easy to get a feel for an area and even carry out detailed roof structure analysis if needed. MultiVision s ability to extract simple 3D building models is also something the planning department will be using shortly. We continue to find more and more uses for oblique photography and MultiVision said James Rutter, GIS Manager at Surrey Heath. Three recent ones come to mind, the first is the street naming and numbering department who are now using it to gain a better understanding of street and industrial estate geography. It was recently used to look at the suitability of individual properties for wheely bin storage. These will be introduced to the borough in September For the recent elections we copied oblique imagery of our polling stations from within MultiVision and have added it to our website making it easier for the public to recognise the buildings being used. From our point of view oblique imagery is a significant value add to our vertical imagery. For most tasks the software is easy to use and no photo interpretation skills are required. Ground features are easy to identify, which cuts down the need for site visits, a real saving in time. It has become indispensable.

4 MultiVision an indispensable tool Dartford Borough Council Dartford Borough Council had its oblique photography flown in 2007 and it is currently used with vertical imagery flown in The time differential between the vertical and the oblique imagery can be a problem in a fast developing area like Dartford but it can also be advantageous when checking for illegal development, i.e. old versus new. Dartford too have a number of different uses for MultiVision and their oblique imagery. It is currently being used by the Council s joint venture with the Police. Whilst the Police do not have direct access to it, those officers who work in the same room as the Council s crime prevention unit benefit from over the shoulder access. They are looking specifically at things like access routes into and out of properties to improve local area knowledge before leaving the building. Knowing exactly what to expect on the ground is especially useful in highly sensitive areas. In many instances this can avoid the need for a site visit altogether. As at Surrey Heath, the planning department uses MultiVision for enforcement and pre-site assessments. It has proved useful for checking new developments in conservation areas where items such as satellite dishes are prohibited. MultiVision is also used as a tool in determining forward planning policy. MultiVision tends to get used ad hoc because it provides a very efficient way of carrying out routine checks. Recently it was used for scanning the borough for industrial air conditioning units, in order to identify businesses which had them, weren t declaring them and were therefore not in compliance with the HSC Approved Code of Practice relating to Legionnaires Disease (ACOP L8). I use MultiVision predominantly for visualisation to support other departments. There was a recent court case for example where the Council had to prove previous land use. We have also produced some extract buildings for simple 3D modelling. It is also used by our Local Land and Property Gazetteer custodian for finding and investigating errors, said Tony Clark, Property Information Manager At Dartford Borough Council. We also use it as a tool to help with mapping new developments. We take the developer s plans, geo-reference them and create new mapping in lieu of Ordnance Survey updates. MultiVision helps to ensure that we get this as accurate as possible. The Winter Garden at Bluewater shopping complex near Dartford in Kent

5 MultiVision an indispensable tool Enfield Council Oblique imagery captured in 2007 is the most recent aerial survey held by Enfield Council. It is combined with older vertical imagery and used extensively with MultiVision for enforcement and pre-site assessments. Being able to check all sides of a property plus any buildings that are not easily accessible even with a site visit is a real benefit. A dozen enforcement officers are currently using MultiVision to routinely check housing extensions for compliance or find those which have no planning approval at all. The same checks are carried out in rural areas, where barns and other storage buildings often get built without planning approval. In Planning, MultiVision is now part of our routine and relied upon as a valuable source of information. We use the application to print off images and copy and paste them into reports. The date of the imagery is crucial because it is possible to see what existed at a particular point in time and having 4 views is very helpful, said Colin Vine, Area Support Officer, Development Services at Enfield Council. We also use it for Tree Preservation Orders. I maintain the TPO tables in our GIS which are plotted on a map and supported by a vertical imagery layer underneath. But very often we need to see more, for example to ascertain which side of a fence a tree is in relation to a property. I use MultiVision to see around the tree where possible to ensure that a tree is allocated to the correct property, continued Vine. In this image MultiVision has been used to spot illegal tree clearance from a wood which is covered by a Tree Preservation Order. The top right hand image shows the extent of the wood.the area of illegal clearance can be viewed from several angles at the corner of the wood Thurrock Thames Gateway Development Corporation The development corporation works in partnership with Thurrock Council to bring new life to existing communities by planning growth and managing investments to create new jobs, businesses and homes, while also improving transport and community services. The Corporation is tasked with bringing 18,500 additional dwellings and 26,000 new jobs to Thurrock by The Development Corporation has taken 15 MultiVision seats to complement its existing MapInfo GIS. As James Bompas, the Development Corporation s Assistant Planner, explains, Using MultiVision it is possible to take measurements, calculate areas, and get a really good idea of a site in prospect and in particular the heights of the buildings, which you can t really appreciate from vertical imagery. It s even possible to extract buildings for modelling purposes.

6 MultiVision an indispensable tool A typical MultiVision screen of the Queen Elizabeth Bridge crossing the Thames at Dartford, fully zoomed out. The point in red on the central vertical aerial image is shown on the surrounding obliques with arrows, indicating the direction of view Particularly impressive is the way in which tracing the mouse up a road in the central image automatically loads new perspective views. This makes it possible to go to a particular point or roam at will, making the software very intuitive to use. We have found, continued Bompas, that most of our users prefer using aerial imagery, compared to maps and, therefore, find MultiVision even more useful. The Corporation has 2007 coverage of both oblique and vertical imagery. Having complete MultiVision coverage for the area makes it easy to gain an appreciation of sites and do quite a lot of preliminary work. We are already using MultiVision for a number of different applications, for example, in assessing planning applications, planning committee presentations, marketing materials, and much more. It s a great tool, which we find invaluable in our work.