This page (revision-31) was last changed on 18-Sep-2012 10:40 by Alison Bennett

This page was created on 14-Jun-2012 13:25 by David Wheatley

Only authorized users are allowed to rename pages.

Only authorized users are allowed to delete pages.

Page revision history

Version Date Modified Size Author Changes ... Change note
31 18-Sep-2012 10:40 750 bytes Alison Bennett to previous
30 18-Sep-2012 10:38 847 bytes Alison Bennett to previous | to last
29 18-Sep-2012 10:38 843 bytes Alison Bennett to previous | to last
28 14-Sep-2012 15:53 777 bytes Alison Bennett to previous | to last
27 29-Aug-2012 14:05 121 KB Paul Gilman to previous | to last
26 27-Jun-2012 15:05 121 KB Administrator to previous | to last
25 27-Jun-2012 12:46 121 KB Administrator to previous | to last
24 27-Jun-2012 12:35 121 KB Administrator to previous | to last
23 14-Jun-2012 16:32 121 KB Lynn Dyson-Bruce to previous | to last
22 14-Jun-2012 16:31 121 KB Lynn Dyson-Bruce to previous | to last
21 14-Jun-2012 16:31 121 KB Lynn Dyson-Bruce to previous | to last

Page References

Incoming links Outgoing links
SectionE
SectionE

Version management

Difference between version and

At line 171 changed one line
Precision and accuracy become significant when comparing disparate datasets is made possible with GIS. These sorts of issues come to the fore in GIS because vector displays can give a spurious impression of highly precise and accurate mapping. Scale, the ratio between distances on the map and in real space, can be manipulated almost infinitely in a vector GIS, as areas are ‘zoomed' or 'panned' to suit. However, simply because it is possible to zoom does not mean that the data thus displayed will be accurate at the new scale. OS contour data, for example, may be digitised from 1:50,000 map sheets, at which scale the smallest distance that can be distinguished is 0.5mm or 5m on the ground. Because this data can be reproduced in the GIS at 1:10,000, at a resolution one fifth of the original, it does not become more accurate. Thus a point captured on screen against a 1:50,000 map base will be accurate at that scale and not progressively more accurate to any larger scale to which the map has been zoomed.
Precision and accuracy become significant when comparing disparate datasets is made possible with GIS. These sorts of issues come to the fore in GIS because vector displays can give a spurious impression of highly precise and accurate mapping. Scale, the ratio between distances on the map and in real space, can be manipulated almost infinitely in a vector GIS, as areas are 'zoomed' or 'panned' to suit. However, simply because it is possible to zoom does not mean that the data thus displayed will be accurate at the new scale. OS contour data, for example, may be digitised from 1:50,000 map sheets, at which scale the smallest distance that can be distinguished is 0.5mm or 5m on the ground. Because this data can be reproduced in the GIS at 1:10,000, at a resolution one fifth of the original, it does not become more accurate. Thus a point captured on screen against a 1:50,000 map base will be accurate at that scale and not progressively more accurate to any larger scale to which the map has been zoomed.
At line 319 changed one line
For this reason ‘padding’ grid references with zeros added to the end of the numbers is a practice that can rarely be justified because, without supporting data, the process of exporting grid references from a text database into GIS can make it impossible to reconstruct whether the location of a find was generalised to the nearest major grid line, or fortuitously aligned with it.
For this reason 'padding' grid references with zeros added to the end of the numbers is a practice that can rarely be justified because, without supporting data, the process of exporting grid references from a text database into GIS can make it impossible to reconstruct whether the location of a find was generalised to the nearest major grid line, or fortuitously aligned with it.
At line 322 changed one line
*ensuring that the HER text databases generally contain information relating to the site location, and recording both how the grid reference was derived and its precision. Points can be created in the HER’s GIS based on grid references exported from monument records in HER text databases while retaining a link between the two systems. Data relating to the accuracy of the grid reference can be exported to the GIS alongside the grid references and used to select an appropriate symbol to depict the point.
*ensuring that the HER text databases generally contain information relating to the site location, and recording both how the grid reference was derived and its precision. Points can be created in the HER's GIS based on grid references exported from monument records in HER text databases while retaining a link between the two systems. Data relating to the accuracy of the grid reference can be exported to the GIS alongside the grid references and used to select an appropriate symbol to depict the point.
At line 347 changed one line
Both in the initial capture of data and for subsequent maintenance and additions in the GIS, there are issues concerning standards which need to be considered if the spatial information is going to be usable. Because many of the outputs of GIS are visual, these pictures can be very persuasive. But GIS are only a model of the real world and the model can only be as good as the quality and appropriateness of the data within it. Data standards help users to control this and to be in a position to say whether data is 'fit for purpose’.
Both in the initial capture of data and for subsequent maintenance and additions in the GIS, there are issues concerning standards which need to be considered if the spatial information is going to be usable. Because many of the outputs of GIS are visual, these pictures can be very persuasive. But GIS are only a model of the real world and the model can only be as good as the quality and appropriateness of the data within it. Data standards help users to control this and to be in a position to say whether data is 'fit for purpose'.
At line 361 changed one line
*__FGDC___ the United States Federal Geographic Data Committee’s Content Standard for Digital Geospatial Metadata is, perhaps, the best known and established of geospatial data standards, the current version having been first released in 1994, and updated in 1998. This standard underpins much of the US Federal Government's work with geospatial data, and is also used by other collectors of spatial data. The standard was recently enhanced, and is available in a variety of commonly used formats.
*__FGDC___ the United States Federal Geographic Data Committee's Content Standard for Digital Geospatial Metadata is, perhaps, the best known and established of geospatial data standards, the current version having been first released in 1994, and updated in 1998. This standard underpins much of the US Federal Government's work with geospatial data, and is also used by other collectors of spatial data. The standard was recently enhanced, and is available in a variety of commonly used formats.
At line 398 changed 2 lines
At present, very few (if any) HERs have made it possible for the general public to directly access spatial information on the internet. There are few technical restrictions on this, with several solutions available for ‘map serving’ or for creating internet interfaces to databases. There are however, currently two main issues preventing this:
#Such projects would be expensive to establish and maintain. Clearly, direct access to ‘live’ data is rarely desirable, and so data must be regularly output from the main HER system usually requiring human intervention. Servers and infrastructure also require management for which few HERs are currently funded. Meeting the requirements of the Freedom of Information Act may change the economics, however.
At present, very few (if any) HERs have made it possible for the general public to directly access spatial information on the internet. There are few technical restrictions on this, with several solutions available for 'map serving' or for creating internet interfaces to databases. There are however, currently two main issues preventing this:
#Such projects would be expensive to establish and maintain. Clearly, direct access to 'live' data is rarely desirable, and so data must be regularly output from the main HER system usually requiring human intervention. Servers and infrastructure also require management for which few HERs are currently funded. Meeting the requirements of the Freedom of Information Act may change the economics, however.
At line 424 added 49 lines
!!E.5.1 Introduction to HLC
Historic Landscape Characterisation (HLC), as applied in England, aims to provide an historic 'time depth' perspective of the landscape.
Traditionally HERs have been based primarily on point, and/or polygonal data on maps, usually limited to specific findspots, buildings or monuments. This leaves parts of the landscape unclassified as to its cultural heritage. These blank spaces on the map may be perceived by those outside the sector as being of no or limited archaeological or historical value. In contrast, the HLC is a total coverage model, although at present it covers primarily the rural landscape. HLC has developed in response to changing outlooks and new government policy.
Using a range of sources, primarily cartographic, HLC assesses and classifies the current landscape in broad historic terms, on the basis of a combination of morphology and interpretation. HLC provides an audit of what has survived within the current landscape, expressed in terms of its historic origins and development. The precise classification and methodology used varies between counties and regions (for more details see ''Taking Stock of the Method'' - Aldred and Fairclough 2003), but the basic principles are similar: a pre-defined series of specific HLC Types or broader Character Types which can be grouped into broad categories based on for example urban, enclosed landscapes and woodlands. The important characteristic is that a time or period element is incorporated. Without placing any hierarchy or value on this analysis it enables an HER to assess what has survived, from what period, so that it may be managed appropriately.
!!E.5.2 Background
HLC builds on Landscape Character Assessment (LCA) carried out by the Countryside Agency to address the need for a new approach to landscape assessment which looked at the whole of England's countryside rather than just specific designated areas. HLC complements LCA in many ways, looking in more detail at historic components of the landscape and increasingly forming a fundamental building block in this landscape assessment process.
For LCA the landscape is assessed in terms of topography, geology and soils, ecology, and culture to allocate areas to a number of generic Landscape Character Types (LCT) which, in conjunction with informed judgement and interpretation are used to build the LCA. They are becoming increasingly GIS based applications and are being used to underpin various landscape management strategies and policies, informing a wide range of issues. Detailed regional LCA's have been brought together to form an overarching national typology, creating broad character areas, resulting in ''The Character of England Map'' (See [CCN website|http://www.ccnetwork.org.uk/] and LCA Types and Areas Maps).
The HLC has also been compared to various LCAs across the UK with varying results (Dyson-Bruce et al 1999, Odell pers. comm., Wakelin pers. comm.) showing similarities in some areas, significant differences in others, although the reasons for this have not yet been fully researched.
!Websites:
Countryside Character Network (CCN) web site [http://www.ccnetwork.org.uk/]. for background to LCA, including methodological developments, speclialised urban LCA, and relationship between HLC and LCA.
Countryside Agency: Topic paper on LCA: [http://www.countryside.gov.uk/Images/LCA_Topic_Paper_5_tcm2-21906.pdf]
!!E.5.3 Development of HLC
From a paper based exercise in the early 1990s HLC has developed to what is, currently, a developing yet sophisticated Geographic Information System (GIS) application. Practitioners not only have to be knowledgeable about archaeology, history and landscapes but also be highly IT and GIS literate. It is GIS which has revolutionised how we perceive spatial data and has enabled the creation of intelligent cogent maps in conjunction with data analysis and manipulation.
!!E.5.4 Methodology
!Historic Landscape Character or Historic Land-use Assessment (HLA): Uniformity of principle
Methodology has generally varied in detail from project to project, but whichever approach has been used HLC/HLA projects all share a number of common elements in that they all:
*assess the total rural landscape
*look at landscape time depth by assessing surviving features
*assess landscape change through history
*assess historic origins of the landscape
*are usually applied at 1:25,000 scale
*apply a well defined (if variable) methodology
*use a specified range of historic landscape types, grouped into themes or categories for example enclosed land, industrial, 20th century, or single attributes, or types for example field types, by form, patterns woodland types for example ancient woodland.
They differ in philosophy and application in that HLA assess the landscape as to current and historic land use as well as historic character, whereas HLC assesses primarily historic character.
!England
In England HLC began with the seminal work carried out in Cornwall in the early/mid 90s (Herring 1998). This was initially a paper based exercise, developed from traditional LCA methodology; but has since become an integrated GIS application (see example figure 48 and 49). To date nearly half of England has reached completion under the leadership of English Heritage in partnership with the relevant Local authorities. (For updates on progress see the [EH web site|http://www.english-heritage.org.uk/server/show/nav.1293])
The East of England (EofE) HLC project, is the only application of HLC in England that uses a single but evolving methodology to ensure a consistency of application and analysis across a region (Dyson-Bruce 2002).
English Heritage commissioned a survey of HLC methodology in 2003 to develop a toolkit for future HLC applications in an attempt to harmonise HLC methodologies and to establish best practice across England. This resulted in 'Taking Stock of the Method' (Aldred and Fairclough 2003). The survey reviewed past methodologies into three major phases of development across England, and from these developed a series of proposals and established standards, as a toolkit for best pratice and future application. This document now informs the methodologies of all current HLC applications in England.
!Websites:
Cornwall HLC: [http://www.cornwall.gov.uk/index.cfm?articleid=5747]
English Heritage: 'Taking Stock of the Method' EH website [http://www.english-heritage.org.uk/server/show/nav.1293](Aldred and Fairclough 2003).
In 2003 English Heritage undertook a detailed review of the various methodologies employed and have proposed an 'HLC Toolkit' to inform future HLC's. This aims to ensure that certain standards are met, and to facilitate a uniformity of approach across England.
This page (revision-31) was last changed on 18-Sep-2012 10:40 by Alison BennettTop