Comparison of Several Change DetectionMethods for Monitoring

Land Cover Dynamics in BelarusMaryna Rymasheuskaya*t

*Dept. of Geodesy and Cadastres, Polotsk State University,Blokhin str. 29, 211440 Novopolotsk, Belarus, email: maryna_456gyahoo.com

tGeoinformatics, Royal Institute of Technology,Drottning Kristinas v. 30, KTH, S-10044 Stockholm, Sweden

Abstract - The study presents experience of use of post- youngest and largest industrial centres in Belarus and isclassification comparison, image differencing, principal located in the basin of Western Dvina in the north of Belarus.component analysis, use of ancillary data and combinations of Amount of atmospheric fallouts from stationary sources indifferent change detection methods for detecting land cover / Novopolotsk city is the highest in Belarus. Industrial andland use dynamics in Novopolotsk area, Belarus over the period residential parts of Novopolotsk are separated from each other1994 - 2002. All methods give good results in terms of accuracyassessment, visual presentation, etc. Change detection results are by foes saitr prtctv zoelhc rteteietadependent on parameters applied, part of the city from pollutants spreading from industrial part

of the city. Forest of sanitary-protective zone is representedmainly by conifers of natural origin, which are replaced by

I. INTRODUCTION deciduous trees near industrial enterprises [1, 10].Monitoring dynamics of land cover and land use is one of Novopolotsk extends fast, many new roads and gas, water

the main applications of change detection methods. Other and sewage pipe lines, etc are constructed recently. Landcommon applications of remote sensing based change cover / land use has been undergone significant changes ondetection are vegetation, wetland, urban, landscape, forest fire the territory of Novopolotsk. The main factors influencinganalysis, etc [5, 6, 7]. There is tens of change detection changes are high tempos of constructions, which beside directmethods developed and used nowadays. Among the most influence on land use led to indirect changes includingcommon methods of change detection using remote sensing changes in subsoil water regimes, and therefore in landdata are post-classification comparison, image differencing, cover/ land use in surrounding areas [1, 10].principal component analysis, multi-date composite image Set of SPOT images from the 24th of July, 1994change detection, spectral mixture analysis, artificial neural (multispectral 20m, panchromatic 10m) and the 19th of July,networks, and integration GIS into analysis as well as 2002 (multispectral 10m) is used in current studies. SPOTcombination of different methods of change detection [4, 5]. images are obtained in the UTM-84 projection.These methods apply different approaches and are used to Land cover change detection schemedetect certain changes. They have advantages anddisadvantages, different levels of difficulties, etc. Land cover change detection scheme used in current studyThe main objectives of current study are i) to discover land was chosen considering local condition, classes of interest,

cover dynamic over the area of Novopolotsk city and reference and ancillary material. Land cover / land usesurroundings, Belarus during the period 1994 - 2002, ii) to classification scheme used for current studies contains thecompare the detection ability of several changes detection following 8 classes:methods considering the most promising, showing the highest * Wateraccuracy according to different authors with their application * Developed (low density residential, high densityto the local conditions and change detection scheme, iii) to residential, commercial / industrial),analyse the errors and uncertainties of change detection as * Transportation,well as and their propagation within the change detection * Open land (sand, clay),process when applying different methods. * Forest (deciduous, coniferous, mixed) and bushes,

II. STUDY SITE AND DATA DISCRIPTION * Grassland,* Agricultural (arable, meadow, gardens),

Monitoring of land is considered as one of the kinds of Wetlan (freste, grad).environmental monitoring included into the National systemof environmental monitoring in Belarus and is conducted onth reua bais Amn th a rea of th prort iners fr The change/no-change land cover detection was also made.environmental monitoring are technogenicaly polluted areasand in particular the city of Novopolotsk. It is one of the

1-4244-0846-6/07/$20.00 ©)2007 IEEE.

III. METHODS spectral change identification methods (pre-

Errors and uncertainties classification spectral change detection) [6, 8],* change detection logic (hard or fuzzy),

In order to ensure as accurate as possible change detection * the classification method (supervised orresults a number of issues should be considered while unsupervised; pixel-based or object-oriented),preparing to and conducting change detection procedure. * the degree of changes to be detectedDifferent factors effects quality of change detection. Ref. 4 ("changed/non-changed" or "from - to" changes),distinguishes environmental (influence of atmospheric * the complexity of change detection procedures:condition such as clouds and humidity; soil moisture ref. 5 suggests 5-level complexity system,conditions; seasonal and plant phenological effects, seasonal * etc.sun angle; topographic effect) and remote sensing (difference Current study is focused on the following methods:in temporal resolution, e.g. djumal sun angle effect; spatial, * post-classification comparison,radiometric, spectral resolution, look angle) factors as having .image differencing,significant affect on change detection quality. One can alsodistinguish methodology factors. m principal component analysis,

The affect of most of these factors can be eliminated or * integration of GIS and ancillary data.decreased by applying proper processing steps. There are The choice of methods tested in current studies is based onmany error sources that are associated with the change results of comparison of change detection methods found indetection using remote sensing data. Among them there are literature, availability of ancillary thematic data, etc. Generaldata acquisition, processing, analysis and conversion, consequence of the change detection procedure is presented inaccuracy assessment and product presentation errors [2]. the figure below.Errors can be divided into positional and attribute errors. State the change detection task,

specifying:

Preprocessing . Area of interest,* Time period,* Classification scheme,Accurate co-registration of multitemporal images is * Change detection logic

probably the most critical issue for land cover/land use vchange detection [13]. It is important for all change detection Raw digital remote sensor Reference and ancillary data

data acquisition collectingmethods. Inaccurate registration of images can lead tooverestimation of actual change [13, 14]. A number ofresearch is dedicated to study of impact of misregistration on Datainvestigation Preprocessinthe change detection results and to reduce its effect on Geometric correction of imagesaccuracy of change detection [2, 3, 9, 11, 13, 14]. Ref. 4

Radiometric correctionrecommends the maximum tolerable RMSE for the purpose nralizatio ofrectgnspurpose ~~~~~~~~(normalization) of imagesof change detection as large as 0.5 pixels. Ref. 8 is ranging it

.1 .2 ix ls. ......................................

There are many other error sources that are associated for Conducting image classification ifchange detection at stages of data acquisition, processing, .necessary of changeanalysis and conversion [2]. Depending on the change informationdetection methods applied the significance of one or another pplyingchangedetectionsource oferrors arise or decrease.

Selection of the accuracy assessmentE.g. post-classification comparison change detection is less methods and sampling scheme Accuracy

"sensitive" to the radiometric correction (normalization) of vassessmentimages but more "sensitive" to choice and accuracy of Creation and analysis of change

detection error matrixindividual image classification method. Analysis of changedetection accuracy is ore com plex than the accuracy

analysis of a single image. Final product generation (digital,hard-copy maps, error evaluation reports,

Change detection methods and etc)

Change detection approaches currently applied for land Fig. I General sequence of land cover / land use changecover / land use change detection can be classified according detection.to different criteria: Image differencing and principal component analysis are

* natural phenomenon to be studied (land use / land "no-change / change" detection methods. Post-classificationcover, forest / vegetation, urban areas, etc) [5] comparison and integration of GIS and ancillary data intoth clsiicto stg in chng deecio change detection analysis are "from-to" change detectionprocedure: methods can be divided into either methods.post-classification change detection methods or

Accuracy assessment ACKNOWLEDGEMENT

The results of methods are compared using change The author would like to thank the CNES, SPOT Imagedetection matrices, performance quality as well as visual distribution, OASIS programme for providing data for currentaspects. Accuracy assessment of change detection results are studies.conducted using common parameters used for accuracy REFERENCESassessment of single remote sensing image such as overallaccuracy, producer's accuracy, user's accuracy and Kappa [1] A. Balbatunou, M. Rymasheuskaya "Mapping of landscape structureaccuracy, producer' accuracyuser'saccuracyandchanges in the zone of well-defined technogenesis" in Conferencecoefficient. Confusion matrix is also used for accuracy proceedings Issues of Complex Mapping and Development ofassessment of change detection results. Interregional GIS of CIS Countries Minsk, BSU, 1999, 38-41.

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