{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,5]],"date-time":"2026-03-05T13:28:17Z","timestamp":1772717297313,"version":"3.50.1"},"reference-count":47,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2021,11,5]],"date-time":"2021-11-05T00:00:00Z","timestamp":1636070400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The important variable of horizontal visibility within forest stands is gaining increasing attention in studies and applications involving terrestrial laser scanning (TLS), photographic measurements of forest structure, and autonomous mobility. We investigated distributions of visibility distance, open arc length, and shaded arc length in three mature forest stands. Our analysis was based (1) on tree position maps and TLS data collected in 2013 and 2019 with three different scanners, and (2) on simulated digital twins of the forest stands, constructed with two pattern-generation models incorporating commonly used indices of tree position clumping. The model simulations were found to yield values for visibility almost identical to those calculated from the corresponding tree location maps. The TLS measurements, however, were found to diverge notably from the simulations. Overall, the probability of free line of sight was found to decrease exponentially with distance to target, and the probabilities of open arc length and shaded arc length were found to decrease and increase, respectively, with distance from the observer. The TLS measurements, which are sensitive to forest understory vegetation, were found to indicate increased visibility after vegetation removal. Our chosen visibility prediction models support practical forest management, being based on common forest inventory parameters and on widely used forest structure indices.<\/jats:p>","DOI":"10.3390\/rs13214455","type":"journal-article","created":{"date-parts":[[2021,11,7]],"date-time":"2021-11-07T20:42:54Z","timestamp":1636317774000},"page":"4455","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Horizontal Visibility in Forests"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0951-7933","authenticated-orcid":false,"given":"Mait","family":"Lang","sequence":"first","affiliation":[{"name":"Tartu Observatory, University of Tartu, 61602 T\u00f5ravere, Estonia"},{"name":"Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Kreutzwaldi 5, 51014 Tartu, Estonia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7458-1467","authenticated-orcid":false,"given":"Andres","family":"Kuusk","sequence":"additional","affiliation":[{"name":"Tartu Observatory, University of Tartu, 61602 T\u00f5ravere, Estonia"}]},{"given":"Kersti","family":"Vennik","sequence":"additional","affiliation":[{"name":"Military Academy, Riia 12, 51010 Tartu, Estonia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9226-2566","authenticated-orcid":false,"given":"Aive","family":"Liibusk","sequence":"additional","affiliation":[{"name":"Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Kreutzwaldi 5, 51014 Tartu, Estonia"}]},{"given":"Kristina","family":"T\u00fcrk","sequence":"additional","affiliation":[{"name":"Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Kreutzwaldi 5, 51014 Tartu, Estonia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1312-6940","authenticated-orcid":false,"given":"Allan","family":"Sims","sequence":"additional","affiliation":[{"name":"Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Kreutzwaldi 5, 51014 Tartu, Estonia"},{"name":"Forest Department, Estonian Environment Agency, Mustam\u00e4e Tee 33, 10616 Tallinn, Estonia"}]}],"member":"1968","published-online":{"date-parts":[[2021,11,5]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"169","DOI":"10.1016\/j.landurbplan.2017.10.010","article-title":"Not seeing the forest for the trees: Modeling exurban viewscapes with LiDAR","volume":"170","author":"Vukomanovic","year":"2018","journal-title":"Landsc. Urban Plan."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1016\/j.compag.2006.03.003","article-title":"A real-time visualization tool for forest ecosystem management decision support","volume":"53","author":"Borges","year":"2006","journal-title":"Comput. Electron. Agric."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"184","DOI":"10.1016\/j.jenvman.2007.01.062","article-title":"Approaches to integrating indicators into 3D landscape visualisations and their benefits for participative planning situations","volume":"89","author":"Wissen","year":"2008","journal-title":"J. Environ. Manag."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"105973","DOI":"10.1016\/j.ecolind.2019.105973","article-title":"Landscape coherence revisited: GIS-based mapping in relation to scenic values and preferences estimated with geolocated social media data","volume":"111","author":"Karasov","year":"2020","journal-title":"Ecol. Indic."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"85","DOI":"10.1016\/j.foreco.2018.04.044","article-title":"Size-growth relationship, tree spatial patterns, and tree-tree competition influence tree growth and stand complexity in a 160-year red pine chronosequence","volume":"424","author":"Looney","year":"2018","journal-title":"For. Ecol. Manag."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"102475","DOI":"10.1016\/j.forpol.2021.102475","article-title":"Building Pareto Frontiers under tree-level forest planning using airborne laser scanning, growth models and spatial optimization","volume":"128","author":"Pascual","year":"2021","journal-title":"For. Policy Econ."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"112170","DOI":"10.1016\/j.rse.2020.112170","article-title":"Mapping functional diversity using individual tree-based morphological and physiological traits in a subtropical forest","volume":"252","author":"Zheng","year":"2021","journal-title":"Remote Sens. Environ."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"5","DOI":"10.1515\/fsmu-2017-0001","article-title":"Online streaming public participation in forest management planning","volume":"66","author":"Korjus","year":"2017","journal-title":"For. Stud. Metsanduslikud Uurim."},{"key":"ref_9","unstructured":"Spurr, S. (1948). Aerial Photographs in Forestry, Ronald Press."},{"key":"ref_10","unstructured":"Dmitriev, I.D., Murahtanov, E.S., and Sukhikh, V.I. (1981). Aerial Photography in Forestry (Lesnaja A\u00e8rofotos\u00ebmka I Aviacija), Lesnaja Promy\u0161lennost\u2019."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"83","DOI":"10.1016\/S0924-2716(99)00014-3","article-title":"A comparison between photogrammetry and laser scanning","volume":"54","author":"Baltsavias","year":"1999","journal-title":"ISPRS J. Photogramm. Remote Sens."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"447","DOI":"10.1016\/j.rse.2016.10.022","article-title":"A nationwide forest attribute map of Sweden predicted using airborne laser scanning data and field data from the National Forest Inventory","volume":"194","author":"Nilsson","year":"2017","journal-title":"Remote Sens. Environ."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"179","DOI":"10.1016\/j.rse.2018.02.069","article-title":"Calibration of nationwide airborne laser scanning based stem volume models","volume":"210","author":"Kotivuori","year":"2018","journal-title":"Remote Sens. Environ."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"77","DOI":"10.2478\/fsmu-2020-0016","article-title":"Remote-sensing support for the Estonian National Forest Inventory, facilitating the construction of maps for forest height, standing-wood volume, and tree species composition","volume":"73","author":"Lang","year":"2020","journal-title":"For. Stud. Metsanduslikud Uurim."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"83","DOI":"10.1016\/S0034-4257(98)00071-6","article-title":"Surface Lidar Remote Sensing of Basal Area and Biomass in Deciduous Forests of Eastern Maryland, USA","volume":"67","author":"Lefsky","year":"1999","journal-title":"Remote Sens. Environ."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1065","DOI":"10.1016\/j.rse.2010.12.011","article-title":"Airborne discrete-return LIDAR data in the estimation of vertical canopy cover, angular canopy closure and leaf area index","volume":"115","author":"Korhonen","year":"2011","journal-title":"Remote Sens. Environ."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"137","DOI":"10.1016\/j.isprsjprs.2018.06.021","article-title":"International benchmarking of terrestrial laser scanning approaches for forest inventories","volume":"144","author":"Liang","year":"2018","journal-title":"ISPRS J. Photogramm. Remote Sens."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"112102","DOI":"10.1016\/j.rse.2020.112102","article-title":"Terrestrial laser scanning in forest ecology: Expanding the horizon","volume":"251","author":"Calders","year":"2020","journal-title":"Remote Sens. Environ."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"68","DOI":"10.1093\/njaf\/27.2.68","article-title":"Spatial tree mapping using photography","volume":"27","author":"Dick","year":"2010","journal-title":"North. J. Appl. For."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"277","DOI":"10.1016\/j.isprsjprs.2020.08.017","article-title":"Performance of terrestrial laser scanning to characterize managed Scots pine (Pinus Sylvestris L.) Stands Is Depend. For. Struct. Var","volume":"168","author":"Yrttimaa","year":"2020","journal-title":"ISPRS J. Photogramm. Remote Sens."},{"key":"ref_21","unstructured":"ATP-3.2.1 (2018). NATO Standard No. 3.2.1: Allied Land Tactics, NATO Standardization Office (NSO). Edition B, Version 1; Technical Report."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Li, Q., Nevalainen, P., Pe\u00f1a Queralta, J., Heikkonen, J., and Westerlund, T. (2020). Localization in unstructured environments: Towards autonomous robots in forests with delaunay triangulation. Remote Sens., 12.","DOI":"10.3390\/rs12111870"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Abegg, M., K\u00fckenbrink, D., Zell, J., Schaepman, M., and Morsdorf, F. (2017). Terrestrial laser scanning for forest inventories\u2014Tree diameter distribution and scanner location impact on occlusion. Forests, 8.","DOI":"10.3390\/f8060184"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Anstey, R.L. (1964). Visibility Measurements in Forested Areas (Special Report S-4), U.S. Army Natick Laboratories. Technical Report.","DOI":"10.21236\/AD0648230"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Drummond, R.R., and Lackey, E.E. (1956). Visibility in Some Forest Stands of the United States (Technical Report EP-36), US Army Quartermaster Research & Development Center, Environmental protection research division. Technical Report.","DOI":"10.21236\/AD0100293"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Al-Amri, M., El-Gomati, M., and Zubairy, M. (2016). The Eye as an Optical Instrument. Optics in Our Time, Springer.","DOI":"10.1007\/978-3-319-31903-2"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1595","DOI":"10.1080\/01431160701736455","article-title":"Two novel methods for field measurements of hydrodynamic density of floodplain vegetation using terrestrial laser scanning and digital parallel photography","volume":"29","author":"Straatsma","year":"2008","journal-title":"Int. J. Remote Sens."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"171","DOI":"10.1016\/j.foreco.2013.03.041","article-title":"Horizon visibility and accuracy of stocking determination on circular sample plots using automated remote measurement techniques","volume":"302","author":"Zasada","year":"2013","journal-title":"For. Ecol. Manag."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"59","DOI":"10.1007\/978-3-642-58136-6_3","article-title":"Radiative transfer in nonhomogeneous plant canopies","volume":"Volume 1","author":"Nilson","year":"1992","journal-title":"Advances in Bioclimatology"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"244","DOI":"10.1016\/S0034-4257(99)00111-X","article-title":"A directional multispectral forest reflectance model","volume":"72","author":"Kuusk","year":"2000","journal-title":"Remote Sens. Environ."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"125","DOI":"10.2478\/fsmu-2020-0019","article-title":"Options for estimating horizontal visibility inhemiboreal forests using sparse airborne laserscanning data and forest inventory data","volume":"73","author":"Lang","year":"2020","journal-title":"For. Stud. Metsanduslikud Uurim."},{"key":"ref_32","unstructured":"Gusakov, S., and Fradkin, A. (1990). Modelling of the Spatial Structure of Forest Ecosystems by Computers, Nauka i Technika."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"69","DOI":"10.1007\/BF02832960","article-title":"Indizes zur Charakterisierung der horizontalen Baumverteilung","volume":"117","author":"Gleichmar","year":"1998","journal-title":"Forstw. Cbl."},{"key":"ref_34","unstructured":"Gadow, K., and Hui, G. (2001). Characterizing forest spatial structure and diversity. Sustainable Forestry in Temperate Regions, Proceedings of the International Workshop Organized at the University of Lund, Sweden, University of Lund."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"15","DOI":"10.1007\/BF00052010","article-title":"A comparison of techniques for assessing dispersion patterns","volume":"40","author":"Goodall","year":"1979","journal-title":"Vegetatio"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"390","DOI":"10.2307\/2529790","article-title":"Statistical analysis of spatial point patterns by means of distance methods","volume":"33","author":"Diggle","year":"1977","journal-title":"Biometrics"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"345","DOI":"10.1093\/biomet\/52.3-4.345","article-title":"Tests of randomness based on distance methods","volume":"52","author":"Holgate","year":"1965","journal-title":"Biometrika"},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Kokhanovsky, A.A. (2013). Database of optical and structural data for the validation of forest radiative transfer models. Radiative Transfer and Optical Properties of Atmosphere and Underlying Surface. Light Scattering Reviews 7, Springer.","DOI":"10.1007\/978-3-642-21907-8"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"418","DOI":"10.1016\/j.rse.2015.08.016","article-title":"The fourth phase of the radiative transfer model intercomparison (RAMI) exercise: Actual canopy scenarios and conformity testing","volume":"169","author":"Widlowski","year":"2015","journal-title":"Remote Sens. Environ."},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Lang, M., Kuusk, A., Kaha, M., Pisek, J., George, J.P., Kiviste, A., Laarmann, D., T\u00fcrk, K., and Arum\u00e4e, T. (2021). Changes during twelve years in three mature hemi-boreal stands growing in radiation model inter-comparison test site, J\u00e4rvselja, Estonia. For. Stud. Metsanduslikud Uurim., 74.","DOI":"10.2478\/fsmu-2021-0007"},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Burkhart, H., and Tom\u00e9, M. (2012). Modeling Forest Trees and Stands, Springer.","DOI":"10.1007\/978-90-481-3170-9"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"437","DOI":"10.1016\/S0168-1923(99)00114-8","article-title":"Inversion of gap frequency data in forest stands","volume":"98-99","author":"Nilson","year":"1999","journal-title":"Agric. For. Meteorol."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"445","DOI":"10.2307\/1931034","article-title":"Distance to nearest neighbor as a measure of spatial relationships in populations","volume":"35","author":"Clark","year":"1954","journal-title":"Ecology"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"390","DOI":"10.2307\/2529790","article-title":"The detection of random heterogeneity in plant populations","volume":"33","author":"Diggle","year":"1977","journal-title":"Biometrics"},{"key":"ref_45","first-page":"1","article-title":"Das Winkelmass-ein Strukturparameter zur Beschreibung der Individualverteilung in Waldbest\u00e4nden","volume":"115","author":"Gadow","year":"1998","journal-title":"Cent. F\u00fcr Das Gesamte Forstwes."},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Tianyang, D., Jian, Z., Sibin, G., Ying, S., and Jing, F. (2018). Single-Tree Detection in High-Resolution Remote-Sensing Images Based on a Cascade Neural Network. ISPRS Int. J. Geo-Inf., 7.","DOI":"10.3390\/ijgi7090367"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1721","DOI":"10.3390\/f6051721","article-title":"A benchmark of lidar-based single tree detection methods using heterogeneous forest data from the Alpine space","volume":"6","author":"Eysn","year":"2015","journal-title":"Forests"}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/21\/4455\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T07:26:38Z","timestamp":1760167598000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/21\/4455"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,11,5]]},"references-count":47,"journal-issue":{"issue":"21","published-online":{"date-parts":[[2021,11]]}},"alternative-id":["rs13214455"],"URL":"https:\/\/doi.org\/10.3390\/rs13214455","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,11,5]]}}}