ORTHOPHOTOGRAPHY FOR RURAL MAP REVISION

The Ordnance Survey (OS) has recently investigated the potential of orthophotography for revision of 1:2500 scale mapping following advances in technology since an earlier investigation in 1973. The results have been compared with stereoplotting on an automated workstation. The background to the investigation and the existing revision methods used for rural areas are described. Orthophotography was produced on a Zeiss 22 Orthocomp at 1:2500 scale using digital height model data supplied from contours (at a 5 m vertical interval) on 1:10000 scale mapping. A pilot block of 20 km² was revised at Kingsbridge, south Devon to assess three levels of revision (local fit, part remedial, and full remedial), using three techniques (orthophotograph overlay, Stereo-orthophoto Plotter and stereoplotting instrument). The quality of the image of the orthophotographs was below that expected for rectified enlargements and the cost of orthophotograph production made the technique uneconomic compared with existing techniques. Orthophotographs were capable of improving the accuracy of revision mapping, but the most cost effective and accurate method was full remedial revision using a Kern PG2 automated workstation.     

Ordnance Survey Policy and Practical Implications for The Revision of Rural Mapping

During 1994 a project was initiated by Ordnance Survey to investigate the requirement for completing the multi-million pound digital revision of 1:2500 scale mapping within Great Britain. This paper, although concentrating on this scale of mapping, discusses the revision policy issues that faced Ordnance Survey and the practical implications arising from implementing the policy for its 1:2500 and 1:10 000 basic scale mapping. Use of contractors was seen as a prime requirement as the resources available within Ordnance Survey were not sufficient to implement the full revision programme. This paper discusses the background to the task and considers the range of photogrammetric options and contractual and quality procedures required for the revision of the mapping over the next few years.     

REVISION OF ORDNANCE SURVEY 1:2500 SCALE MAPS

With the completion of its programme to produce a national series of 1:2500 scale maps of rural areas, the Ordnance Survey is now faced with the major task of maintaining it up to date and making the revision information available to map users. The organisation and techniques for this are discussed, as are a number of innovations which are being considered.

Résumé

Avec l'achèvement du programme de réalisation de la série cartographique nationale à l'échelle du 1:2500 des régions rurales, l'Ordnance Survey doit maintenant faire face au maintien à jour de cette série et à la mise à disposition des usagers des données de révision, ce qui va constituer sa tâche principale. Une discussion sur l'organisation et les techniques correspondantes est fournie, prenant en compte l'examen de nombreuses innovations.

Zusammenfassung

Nach Fertigstellung der Kane 1:2500 von ländlichen Gebieten besteht für den Ordnance Survey jetzt die Aufgabe, diese Karte laufend zu halten und die Ergänzungen den Kartennutzern bereitzusteller. Diskussion der Organisation und Verfahren dafür sowie einiger Neuerungen, die in Erwägung gezogen werden.     

A LOGARITHMIC AREA-COMPUTING SCALE

Abstract

The computing scale to be described is based on the principle of the logarithmic slide-rule and has been devised for the rapid and accurate evaluation of quadrilateral areas from cadastral field sheets on the 1/2500 and larger scales.     

The application of GPS precise point positioning technology in aerial triangulation

In traditional GPS-supported aerotriangulation, differential GPS (DGPS) positioning technology is used to determine the 3-dimensional coordinates of the perspective centers at exposure time with an accuracy of centimeter to decimeter level. This method can significantly reduce the number of ground control points (GCPs). However, the establishment of GPS reference stations for DGPS positioning is not only labor-intensive and costly, but also increases the implementation difficulty of aerial photography. This paper proposes aerial triangulation supported with GPS precise point positioning (PPP) as a way to avoid the use of the GPS reference stations and simplify the work of aerial photography.Firstly, we present the algorithm for GPS PPP in aerial triangulation applications. Secondly, the error law of the coordinate of perspective centers determined using GPS PPP is analyzed. Thirdly, based on GPS PPP and aerial triangulation software self-developed by the authors, four sets of actual aerial images taken from surveying and mapping projects, different in both terrain and photographic scale, are given as experimental models. The four sets of actual data were taken over a flat region at a scale of 1:2500, a mountainous region at a scale of 1:3000, a high mountainous region at a scale of 1:32000 and an upland region at a scale of 1:60000 respectively. In these experiments, the GPS PPP results were compared with results obtained through DGPS positioning and traditional bundle block adjustment. In this way, the empirical positioning accuracy of GPS PPP in aerial triangulation can be estimated. Finally, the results of bundle block adjustment with airborne GPS controls from GPS PPP are analyzed in detail.The empirical results show that GPS PPP applied in aerial triangulation has a systematic error of half-meter level and a stochastic error within a few decimeters. However, if a suitable adjustment solution is adopted, the systematic error can be eliminated in GPS-supported bundle block adjustment. When four full GCPs are emplaced in the corners of the adjustment block, then the systematic error is compensated using a set of independent unknown parameters for each strip, the final result of the bundle block adjustment with airborne GPS controls from PPP is the same as that of bundle block adjustment with airborne GPS controls from DGPS. Although the accuracy of the former is a little lower than that of traditional bundle block adjustment with dense GCPs, it can still satisfy the accuracy requirement of photogrammetric point determination for topographic mapping at many scales.     

EVALUATION OF METRIC CAMERA PHOTOGRAPHY FOR MAPPING AND CO-ORDINATE DETERMINATION

Rigorous photogrammetric methods have been used to carry out a detailed evaluation of Metric Camera panchromatic photographs of two areas, one in south-east France and the other on the coast of Libya. Inner, relative and absolute orientation and space resection were performed in order to determine how accurately ground co-ordinates can be obtained and the most suitable scale for mapping. Results of absolute orientation (residuals of 19m in plan and 26m in height) indicate that it is possible to produce maps at 1:100000 scale with contours at 100m intervals. Plotting has been done at 1:100000 scale showing cultural and drainage features. It was not possible to identify all detail which is plotted on existing 1:100000 scale line maps.     

The Geocoding of Synthetic Aperture Radar Imagery and an Application to Nautical Charting

An ERS-1 SAR image of Frankfurt was geocoded using a variety of DEM spatial resolutions to examine the influence on positional accuracy compared with control points derived from a 1:50 000 scale map of the same area. It was demonstrated that mapping to 1:50 000 scale was possible in flat areas with a DEM resolution finer than 200 m. The case for SAR imagery in nautical charting is discussed in the light of these results, drawing on recent experiences at the Hydrographic Office in charting the South Orkney Islands.     

Observational Scale and Modeled Potential Residential Loss from a Storm Surge

Two geographically related questions with regard to hurricane-induced storm-surge impacts were investigated: (1) What observational scale of analysis is appropriate? (2) Is the effect of observational scale on model results predictable? These two research questions were investigated in the context of storm surge-induced impacts to single-family residential structures in Florida. The study was conducted for 21 coastal counties in Florida at five spatial scales of analysis: parcel, block, block group, tract, and county. The research findings reveal a monotonically decreasing relationship between predicted standardized residential loss (the ratio of predicted loss at scale X and the predicted loss at parcel scale) and the observational scale of analysis. This monotonic relationship was consistent for most Florida counties, primarily due to the notable spatial distribution of housing units and proximity to the coastline.     

航空数字摄影测量对林分立木测高及精度分析

为了解决以往森林调查手段需要在野外工作,并且比较耗费人力、物力与时间的问题,本文提出用航空摄影立体像对数字摄影测量的方法来估测林分立木高度。本研究利用两张廊坊市自然公园拍摄比例尺为1∶2500的航空像对,构建数字立体模型,在此模型上测量50株样木的高度,并结合实地用全站仪实测得出的数据进行精度的分析评价。结果表明:利用航空立体像对数字摄影测量立木高度,与全站仪实测数据相比差异不显著,两组数据呈线性正相关关系,精度达到93.96%,与林业调查上95%的精度要求较为接近。     

Experiments in the Design of 1:100 000 Scale Topographic Mapping for Great Britain

Abstract

Most European countries have a national topographic map series at 1:100 000 scale, but currently Great Britain does not. The history of mapping at or around 1:100 000 in Britain is described briefly and consideration given as to why such a scale would be appropriate for a national series of mapping aimed at tourist and leisure users. The main focus of the article is to review a series of 1:100 000 scale maps of two sample areas of Great Britain, produced in the style of various western European medium scale topographic maps. Two further design examples are produced combining desirable characteristics of the maps examined. The results show both that many of the designs translate well to 1:100 000 scale maps of the British landscape and that there is considerable potential for a topographic base at this scale providing a basis for a national series aimed at tourist and leisure users.     

北京市大比例尺地形图图幅号查询信息系统的研制

供应大比例尺地形图是城市测绘资料管理部门的基本职能。文中论述了在ARC／INFO基础上,以1：25000比例尺地形图上的点、线、面地物为索引,查询北京市1：500～1：10000各类比例尺地形图图幅号的算法。实验表明系统是实用的。     

METRIC CAMERA DATA: ASSESSMENT AND POTENTIAL USE AT L'INSTITUT GÉOGRAPHIQUE NATIONAL

A short review is given of the involvement of the Institut Géographique National (IGN) in the European Space Agency Spacelab Metric Camera (MC) experiment. IGN has participated in this project from the early stages of its preparation in 1974. The assessment of MC data has been carried out for both metric and thematic purposes. Using a Matra Traster analytical plotter, a contoured map of Carpentras. included in the European standard test site of Marseille, has been prepared at a scale of 1:100 000 with 100 m and 50 m contour intervals. Preliminary comparison of this map with the topographic data base shows a height accuracy of about 30 m. Orthophotographs have been produced of the same area, at 1:100000 scale and at 1:250000 scale. showing good agreement with the basic line map. An infrared colour pseudo-orthophotograph has been produced for Khartoum (assuming that the ground was flat) and a space map of a desert area of Algeria has been printed at 1:200000 scale, allowing a good comparison with the drainage shown on the existing line map. Interpretation of the MC photography has also been assessed and compared with conventional IGN aerial photography taken over the European standard test site. Due to the low sun elevation and the apparent image motion which affected the MC photography, the result is not as good as was expected. Some linear features of 6m width are visible (for example, roads and hedges) but for positive identification a width of 18m is necessary. It is difficult to determine the extent of cities and land parcels less than 40 × 40m are not visible. However, the MC data can be used for checking and revising some features of small scale maps (smaller than 1:100000). Two experiments have been performed in thematic interpretation, one concerned with land use and the other with forest mapping. Some improvements of the MC are suggested in order to satisfy the major requirements of users while the possibilities of topographic mapping from these data are summarised.     

Why Maps Matter in GIScience

Abstract

This paper is an elaboration of the theses proposed in ‘Cartographic presentation of forms and degradation of the natural environment: sozological map on a scale of 1∶50?000’ (), where a sozological map of Poland was presented. The said map contained comprehensive cartographic information on the forms of environmental protection and degradation, made to a scale of 1∶50?000. The thematic scope of the map has already been modified twice: in 1997 and in 2005, with the ensuing changes presented in corresponding manuals: Sozological Map on a Scale of 1∶50?000, in an Analogue and Digital Form (Chief National Geodesist, 1997) and Technical Guidelines GIS-4. Sozological Map of Poland, Scale of 1∶50?000, in an Analogue and Digital Form (2005). Many years’ worth of experience gained since the launch of this cartographic system points out to the need for broadening the presented content and improving the map’s scale. Thus, attempts have been made at rescaling the map to 1∶10?000. Increasing the degree of detail is particularly necessary for presenting areas of intensive human activity. In this paper, the authors propose technical and graphical solutions for the 1∶10?000 scale.     

Bathymetrical influences on spatial and temporal characteristics of chlorophyll-a concentrations in the Southern Ocean from 2002 to 2012 (October to March) using MODIS

Phytoplankton blooms, particularly in the Southern Ocean, can have significant impact on global biogeochemistry cycling. To investigate the accuracy of chlorophyll-a distribution, and to better understand the spatial and temporal dynamics of phytoplankton biomass, we examine chlorophyll-a estimates (October–March from 2002 to 2012) derived from Moderate Resolution Imaging Spectrometer (MODIS) data following the ocean chlorophyll-a 3 model (OC3M) algorithm. Noticeable seasonality occurs in the temporal distribution of chlorophyll-a concentrations, which shows the highest value in December and January and an increasing tendency during the 2002–2012 period. The spatial distribution of chlorophyll-a varies greatly with latitude, as higher latitudes experience more phytoplankton blooms (chlorophyll-a concentration larger than 1 mg/m³) and marginal seas (Ross Sea and Amundsen Sea) show different bloom anomalies caused by two dominant algae species. Areas at higher latitudes and shallow water (<500 m) experience the shorter ice-free periods with greater seasonality. A noticeable bathymetry gradient exists at 2500-m isobaths, while water at the 500–2500-m depth experiences quite long ice-free periods with a stable water environment. Blooms generally occur near topographic features where currents have strong interactions when the water depth is more than 2500 m. Based on these findings, we can classify the Southern Ocean into two bloom subregions, 0–500 m as an enhanced bloom zone (EBZ), and 500–2500 m as a moderate bloom zone (MBZ). The EBZ has a quite high-bloom probability of about 30%, while the MBZ has only 10%.     

Measuring Off Cropped Enlargements with a Digitizing Tablet

A standard digitizing tablet was used to measure objects off cropped enlargements (1:1000 scale), with an absolute accuracy of 0.75 m. Interior orientation for the enlargements was based upon camera reference marks captured from the original photographs, ranging from 1:6000 to 1:15 000 scale. Control for exterior orientation was provided by 1:1000 scale maps. Operational procedures are outlined, followed by results from eight sample photographs. Particular attention is devoted to errors that influence measurement accuracy.     

Scale Effects on Chlorophyll-A Concentration Retrieved: Assessment and Validation Using Indian Remote Sensing Satellite

To understand the scale effects on chlorophyll-a (chl-a) concentration retrieved from satellite images, the two-band algorithm (TA) and three-band algorithm (TBA) were constructed for estimating chl-a from satellite images. Two synchronous images of Advanced Wide-Field Sensor (AWiFS) and Linear Imaging Self-Scanner (LISS) of Indian remote sensing satellite were used to assess and validate the scale errors of these two algorithms. They were collected at local time 02:55:46:471 and 02:58:25:053 on October 8, 2005 in Yellow River Estuary, and their spatial resolutions are 24 m and 56 m, respectively. From the results of this study, it was found that: (1) the relative scale error (RSE) of TA and TBA, caused by scale changing from LISS to AWiFS, varied from 0% to 100%; (2) the RSE was correlated with the spatial non-homogeneous degree of chl-a distribution; and (3) using TBA to estimate chl-a concentration in Yellow River Estuary decreased 2.55% of model uncertainty, but increased 4.97% of scale errors, in comparison with TA. Additionally, the study indicated that the performance of algorithms for chl-a estimation was greatly affected by the scale error. If the scale effects of chl-a retrieval algorithm were taken into consideration, TA had a superior performance to the TBA in this study.     

空间实验室图像的制图能力分析及其地学应用——以西藏日喀则地区和珠峰地区的试验为例

本文论述了空间实验室测量相机(MC)拍摄的彩色红外立体像对在中比例尺地形制图、正射影像地图以及土地资源调查中的应用可能性,给出1:10万和1:20万比例尺的制图例证,表明平面位置和高程精度能满足1:10万比例尺地形图规范要求;1:10万比例尺影像图可以满足专题制图精度要求。 应用数字图像处理技术,将二种来源(MC,MSS)的遥感数据做数字匹配,并进行信息提取、组合、增强和分类等处理,其结果与原始图像比较表明有独特的优越性,与MSS原始数据相比,图像的空间分辨率明显提高,各种类型界线更分明,可分辨类目增多;而与MC原始图像相比,其光谱特性获得改善且能保持原有的空间分辨率。土地利用类型解释精度与MSS和MC原始图像比较分别提高7—20％左右。     

THE IGN (FRANCE) TOPOGRAPHIC DATABASE

The French topographic database is a three dimensional database whose content is very near to that of the IGN 1:25 000 scale maps. It has a metric accuracy and is designed to have three aims (maps at scales of 1:25 000 and 1:50 000 and the topographic part of the cadastral map at 1:5000 scale, providing located structured data). The structure, including topology information, is described. The process of data capture is based on photogrammetry and field completion. Experiments concerned with revision are being made in order to define the methodology precisely.     

Analyzing the effects of scale and land use pattern metrics on land use database generalization indices

The generalization index system is one of the critical issues for computer-aided land use database generalization. This paper studies the scale and land use pattern effects on land use database generalization indices and estimates the thresholds of these indices based on a typical land use database sample. The index system of land use database generalization is discussed and constructed from macro and micro perspectives. Six land use pattern metrics, namely, land use diversity index, land use dominance index, land use homogeneity index, land use fragmentation index, the index of land use type dominance, and the index of land use type fragmentation, are designed to characterize land use patterns and are introduced into the analysis of land use pattern effect on land use database indices. The analysis framework of the scale and land use pattern effects on the land use database indices are proposed by employing statistical techniques. Based on the land use database samples at multiple spatial scales collected in various land use regions across China, the study generates rules for both scale and land use pattern effects on the indices, including map area proportion of land use types, total map load, parcel map load, and minimum parcel area. The thresholds of these indices in land use database generalization are produced at the scales of 1:50,000, 1:100,000, 1:250,000, and 1:500,000. An experimental generalization at county level demonstrates how to determine the generalization index values considering scale and land use pattern, and how to evaluate the generalization results using our macro indices.