Some Personal Errors in Point Sampling

Munro, Donald D.

doi:10.5558/tfc42407-4

The Forestry Chronicle

1966

DOI: 10.5558/tfc42407-4

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Some Personal Errors in Point Sampling

Donald D. Munro¹

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“…This is mainly because of the difficulty in obtaining well-founded quantitative estimates of the errors and the lack of generalities in the results. Estimates of measurement errors in point sampling have been obtained among others, by Ker et al (1957);Carow (1958); Kendal et al (1959); Munro (1966); Carow and Rickerd (1969);and Laar (1970) mainly ~ouglas-fi; (Pseudotsuga menziesii (Mirb.) ~ranco): western hemlock (Tsuga heterophylla (Raf.)…”

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confidence: 99%

Personal Bias in Forest Measurements

Omule¹

1980

The Forestry Chronicle

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The assumption that measurement errors are negligible during a forest inventory was tested using forestry students. The magnitude of personal bias in measuring tree diameter at breast height (dbh), total height, and basal area Rer hectare was obtained. Bias was negligible in dbh measurements and the among-crew coefficient of variation (CV) was 8.16%. Heights were significantly underestimated and the among-crew CV was 21.86%. The percentage error in basal area Der hectare determination was 4.09% at the measurement biases are summarized by Loetsch et al. (1973); and for dbh, the most notable is the work of Myers (1961).It has been suggested that if the measurement errors occur randomly, their effect approaches zero. In this paper, the assumption that measurement errors are negligible during a forest inventory was tested. Specifically, the magnitude of personal bias and variation in measuring tree dbh, tree total height, and stand basal area was determined. 95% probability level, using a prism of basal area factor 6. Measurement errors are., in general, not negligible. Their rnagn~tude Method of Data Collectionshould be estimated per inventory and included in the total error of the inventory estimate.Data for the study were collected at the University of British Columbia Research Forest, Maple Ridge, B.C., during the third year forestry students' field school in mensuration. ROsum6Sixty sampling points were systematically set at about 80-m intervals in a 70-year-old second growth stand containinaLe fait que les erreurs de mesurage s'avbrent n6gligeables.lors d'inventaire forestier a BtB verifie avec des Btudiants en foresterie. On calcula I'importance de I'influence du personnel mesurant le diametre de I'arbre a hauteur de poitrine (1,30 m), la hauteur totale et la surface terriere a I'hectare. Celle-ci fut donc negligeable pour les mesures du diametre et le coefficient de la variation (CW entre les membres d'une mbme Bquipe se chiffra 8.16%. Par contre les prises de la hauteur furent fortement sous-estim6es et le coefficient de la variation (CV) entre les membres d'une mbme equipe se fixa a 21.86%. Le pourcentage d'erreur enregistre pour le calcul de la suface terriere a I'hectare fut de 4.09% suivant le taux de probabilite de 95% et utilisant un prisme facteur 6 pour cet item. En general, les erreurs de mesurage ne sont pas negligeables. Leur importance devrait btre estimee pour chaque inventaire en plus d'6tre incluse dans l'erreur totale de I'inventaire.

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confidence: 99%

Personal Bias in Forest Measurements

Omule¹

1980

The Forestry Chronicle

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Accuracy in estimating basal areas for forest inventories: comparison of Android-based virtual relascope and Spiegel Relaskop

2021

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The potential for using smartphones extends to forest inventory. Several applications allow the estimation of basal areas, transforming the device into a low-cost virtual relascope. The accuracy of the Bitterlich relascope application was analysed using four low-performance devices. The results were compared with those of a Spiegel Relaskop. The measurements were taken with artificial targets; this increased the discrimination of the results in comparison with tests made by counting trees. To check the accuracy in real field conditions, the Bitterlich relascope application was compared to a Spiegel Relaskop. No significant differences in accuracy were found between the data obtained by the traditional relascope and by the Android devices, neither for the artificial target nor in field conditions. The obtained biases were also similar between the Spiegel Relaskop and the devices tested. To achieve high-quality measurements with the smartphones a realistic calibration, resembling forest inventory is needed.

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Some Personal Errors in Point Sampling

Cited by 2 publications

References 2 publications

Personal Bias in Forest Measurements

Personal Bias in Forest Measurements

Accuracy in estimating basal areas for forest inventories: comparison of Android-based virtual relascope and Spiegel Relaskop

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