Proceedings of the Symposium on Global and Environmental Monitoring: Proceedings of the Symposium on Global and Environmental Monitoring

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Persistent identifier:: 856665355

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts ; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856665355

Language:: English

Document type:: Multivolume work

Volume

Persistent identifier:: 856669164

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Scope:: XIV, 912 Seiten

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856669164

Illustration:: Illustrationen, Diagramme, Karten

Signature of the source:: ZS 312(28,7,1)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: International Society for Photogrammetry and Remote Sensing, Commission of Photographic and Remote Sensing Data

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: [WP-3 FOREST INVENTORY APPLICATIONS]

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: REMOTE SENSING-AIDED SURVEY OE RENEWABLE RESOURCES WITH EMPHASIS ON FORESTRY IN THE TROPICS. Simo Poso

Document type:: Multivolume work

Structure type:: Chapter

433 REMOTE SENSING-AIDED SURVEY OE RENEWABLE RESOURCES WITH EMPHASIS ON FORESTRY IN THE TROPICS Simo Poso University of Helsinki Department of forest Mensuration and Management Unioninkatu 40 B, 00170 Helsinki, Finland ISPRS Commission VII ABSTRACT The principles of two-phase sampling procedures for forest resource assessments are described. In the first phase, data from auxiliary sources (e.g. maps, satellite imagery, aerial photographs, old forest inventory data, forest growth models) are used singly or in combination to form strata. In the second phase, actual ground measurement data are then transferred to the first phase units; each plot belong ing to the same stratum obtains egual ground truth estimates. The problem of using many data sources is that the number of strata tends to grow too high causing difficulties in getting a sufficient number of ground truth measurements. The solution introduced in the paper is to apply many separate stratifications based on different data sources which produces many estimates for first-phase sample units. The final estimates may be based on weighting using of inverse of error variance or on a specific expert system. KEY WORDS: Forest inventory, Remote sensing, Two-phase sampling 1. INTRODUCTION There is a large number of alternative approach es that can be adopted for forest resource as sessments. These approaches can be roughly di vided into two categories: (1) to mapping for area classification and (2) to sampling proce dures. The differentiation of the above catego ries is not always unambiguous as many combina tions may exist. In mapping approaches the whole area is divided into a certain number of different categories such as forests, woodlands, other land uses. Different categories, i.e. classes, are diffe rentiated by drawing borderlines on maps or oth er base material, such as satellite imageries and aerial photographs. If remote sensing is used distortions should be known and elimina ted. The areas of different classes can then be measured on the base material. Sampling approaches involve locating a number of sampling units, usually circular plots or relas- cope points, in a systematic pattern in the in ventory area. Data are measured or estimated for each unit and the inventory results, including area distributions and mean values as well as reliability estimates, are calculated on the ba sis of the samples. The principal advantages and disadvantages of mapping approach may be listed as follows: + traditional, easy to understand + suitable for overall viewing - borderlines between classes are often ambig uous and subjective - variation within a class is often large - classes are often difficult to measure accu rately in the field (estimates often based largely on ocular estimations) - monitoring of changes is difficult if based on more or less subjective area delineation Generally, it is recommended to use a sampling technigue for national forest inventories in order to get detailed and non-biased informa tion for planning purposes. The purpose of this paper is to illustrate an application of sampling technigue together with the use of remote sensing in order to avoid the disadvantages associated with mapping. The tech nigue demonstrated is based on two-phase samp ling. In the first phase, auxiliary data is ob tained from many kinds of sources, such as maps, satellite imagery, aerial photographs. In the second phase, data are usually measured in the field. The sample for the first-phase data is an intensive one and the sample for second-phase data is a sub-sample of the first-phase sample. The final results are the better the higher is the correlation between the first- and second- phase data. 2. METHODOLOGICAL DESCRIPTION A combination of remote sensing and ground truth

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