{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,20]],"date-time":"2026-01-20T03:35:14Z","timestamp":1768880114055,"version":"3.49.0"},"reference-count":28,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2016,12,24]],"date-time":"2016-12-24T00:00:00Z","timestamp":1482537600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["31201128"],"award-info":[{"award-number":["31201128"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"name":"&quot;Young Faculty Study Abroad Program&quot; of Northwest A&amp;F University Scholarship Fund"},{"name":"Shaanxi science and technology overall planning and innovation project","award":["2014KTCL02-15"],"award-info":[{"award-number":["2014KTCL02-15"]}]},{"name":"science and technology project of Northwest A&amp;F University","award":["Z222021560"],"award-info":[{"award-number":["Z222021560"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Orchard target-oriented variable rate spraying is an effective method to reduce pesticide drift and excessive residues. To accomplish this task, the orchard targets\u2019 characteristic information is needed to control liquid flow rate and airflow rate. One of the most important characteristics is the canopy density. In order to establish the canopy density model for a planar orchard target which is indispensable for canopy density calculation, a target density detection testing system was developed based on an ultrasonic sensor. A time-domain energy analysis method was employed to analyze the ultrasonic signal. Orthogonal regression central composite experiments were designed and conducted using man-made canopies of known density with three or four layers of leaves. Two model equations were obtained, of which the model for the canopies with four layers was found to be the most reliable. A verification test was conducted with different layers at the same density values and detecting distances. The test results showed that the relative errors of model density values and actual values of five, four, three and two layers of leaves were acceptable, while the maximum relative errors were 17.68%, 25.64%, 21.33% and 29.92%, respectively. It also suggested the model equation with four layers had a good applicability with different layers which increased with adjacent layers.<\/jats:p>","DOI":"10.3390\/s17010031","type":"journal-article","created":{"date-parts":[[2016,12,28]],"date-time":"2016-12-28T11:22:14Z","timestamp":1482924134000},"page":"31","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":22,"title":["A Canopy Density Model for Planar Orchard Target Detection Based on Ultrasonic Sensors"],"prefix":"10.3390","volume":"17","author":[{"given":"Hanzhe","family":"Li","sequence":"first","affiliation":[{"name":"College of Mechanical and Electronic Engineering, Northwest A&amp;F University, Yangling 712100, China"}]},{"given":"Changyuan","family":"Zhai","sequence":"additional","affiliation":[{"name":"College of Mechanical and Electronic Engineering, Northwest A&amp;F University, Yangling 712100, China"},{"name":"Department of Biosystems and Agricultural Engineering, Oklahoma State University, Stillwater, OK 75078, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0676-2925","authenticated-orcid":false,"given":"Paul","family":"Weckler","sequence":"additional","affiliation":[{"name":"Department of Biosystems and Agricultural Engineering, Oklahoma State University, Stillwater, OK 75078, USA"}]},{"given":"Ning","family":"Wang","sequence":"additional","affiliation":[{"name":"Department of Biosystems and Agricultural Engineering, Oklahoma State University, Stillwater, OK 75078, USA"}]},{"given":"Shuo","family":"Yang","sequence":"additional","affiliation":[{"name":"College of Mechanical and Electronic Engineering, Northwest A&amp;F University, Yangling 712100, China"}]},{"given":"Bo","family":"Zhang","sequence":"additional","affiliation":[{"name":"College of Mechanical and Electronic Engineering, Northwest A&amp;F University, Yangling 712100, China"}]}],"member":"1968","published-online":{"date-parts":[[2016,12,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"124","DOI":"10.1016\/j.compag.2011.09.007","article-title":"A review of methods and applications of the geometric characterization of tree crops in agricultural activities","volume":"81","author":"Rosell","year":"2012","journal-title":"Comput. Electron. Agric."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"691","DOI":"10.3390\/s140100691","article-title":"Advanced technologies for the improvement of spray application techniques in Spanish viticulture: An overview","volume":"14","author":"Gil","year":"2014","journal-title":"Sensors"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"250","DOI":"10.1016\/j.scitotenv.2015.08.012","article-title":"Influence of liquid-volume and airflow rates on spray application quality and homogeneity in super-intensive olive tree canopies","volume":"537","author":"Gil","year":"2015","journal-title":"Sci. Total Environ."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"319","DOI":"10.1080\/10798587.2015.1015781","article-title":"Technology Application of Smart Spray in Agriculture: A Review","volume":"21","author":"Song","year":"2015","journal-title":"Intell. Autom. Soft Comput."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"475","DOI":"10.13031\/2013.2728","article-title":"Tree shape and volume measurement by light interception and aerial photogrammetry","volume":"43","author":"Meron","year":"2000","journal-title":"Trans. ASAE"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1158","DOI":"10.1111\/j.1365-3040.2005.01353.x","article-title":"Foliage randomness and light interception in 3-D digitized trees: An analysis from multiscale discretization of the canopy","volume":"28","author":"Sinoquet","year":"2005","journal-title":"Plant Cell Environ."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1016\/j.compag.2004.10.002","article-title":"Software development for real-time ultrasonic mapping of tree canopy size","volume":"47","author":"Schumann","year":"2005","journal-title":"Comput. Electron. Agric."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"331","DOI":"10.13031\/2013.18448","article-title":"Variable rate nitrogen application in Florida citrus based on ultrasonically-sensed tree size","volume":"21","author":"Zaman","year":"2005","journal-title":"Appl. Eng. Agric."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"2459","DOI":"10.3390\/s110302459","article-title":"Performance of an ultrasonic ranging sensor in apple tree canopies","volume":"11","author":"Escola","year":"2011","journal-title":"Sensors"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2177","DOI":"10.3390\/s110202177","article-title":"Ultrasonic and LIDAR sensors for electronic canopy characterization in vineyards: Advances to improve pesticide application methods","volume":"11","author":"Llorens","year":"2011","journal-title":"Sensors"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"149","DOI":"10.1016\/j.compag.2014.12.015","article-title":"Ultrasonic sensing of pistachio canopy for low-volume precision spraying","volume":"112","author":"Maghsoudi","year":"2015","journal-title":"Comput. Electron. Agric."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"587","DOI":"10.5545\/sv-jme.2011.015","article-title":"Design and Testing of an Ultrasound System for Targeted Spraying in Orchards","volume":"57","author":"Jejcic","year":"2011","journal-title":"Stroj. Vestnik J. Mech. Eng."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"15500","DOI":"10.3390\/s121115500","article-title":"Programmable ultrasonic sensing system for targeted spraying in orchards","volume":"12","author":"Stajnko","year":"2012","journal-title":"Sensors"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"2902","DOI":"10.3390\/s150202902","article-title":"Testing accuracy of long-range ultrasonic sensors for olive tree canopy measurements","volume":"15","author":"Llorens","year":"2015","journal-title":"Sensors"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1505","DOI":"10.1016\/j.agrformet.2009.04.008","article-title":"Obtaining the three-dimensional structure of tree orchards from remote 2D terrestrial LIDAR scanning","volume":"149","author":"Rosell","year":"2009","journal-title":"Agric. For. Meteorol."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"175","DOI":"10.1016\/j.compag.2013.08.013","article-title":"Real-time positioning algorithm for variable-geometry air-assisted orchard sprayer","volume":"98","author":"Osterman","year":"2013","journal-title":"Comput. Electron. Agric."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"153","DOI":"10.1016\/j.agrformet.2012.11.013","article-title":"Relationship between tree row LIDAR-volume and leaf area density for fruit orchards and vineyards obtained with a LIDAR 3D Dynamic Measurement System","volume":"171\u2013172","author":"Sanz","year":"2013","journal-title":"Agric. Forest Meteorol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"78","DOI":"10.1016\/j.biosystemseng.2014.06.001","article-title":"Deciduous tree reconstruction algorithm based on cylinder fitting from mobile terrestrial laser scanned point clouds","volume":"124","author":"Sanz","year":"2014","journal-title":"Biosyst. Eng."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"3671","DOI":"10.3390\/s150203671","article-title":"Towards an optimized method of olive tree crown volume measurement","volume":"15","author":"Llorens","year":"2015","journal-title":"Sensors"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"24","DOI":"10.1016\/j.compag.2012.03.009","article-title":"Prediction of leaf area index in almonds by vegetation indexes","volume":"85","author":"Whiting","year":"2012","journal-title":"Comput. Electron. Agric."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"610","DOI":"10.1016\/j.scienta.2013.10.009","article-title":"Canopy leaf area index for apple tree using hemispherical photography in arid region","volume":"164","author":"Liu","year":"2013","journal-title":"Sci. Hortic."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"425","DOI":"10.1007\/s11119-015-9387-8","article-title":"Estimating light interception in tree crops with digital images of canopy shadow","volume":"16","author":"Metcalf","year":"2015","journal-title":"Precis. Agric."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"516","DOI":"10.3390\/s130100516","article-title":"Use of a terrestrial LIDAR sensor for drift detection in vineyard spraying","volume":"13","author":"Gil","year":"2013","journal-title":"Sensors"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"14662","DOI":"10.3390\/s131114662","article-title":"Discriminating crop, weeds and soil surface with a terrestrial LIDAR sensor","volume":"13","author":"Andujar","year":"2013","journal-title":"Sensors"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"253","DOI":"10.1006\/bioe.2002.0082","article-title":"Comparison of Different Spray Volume Deposition Models Using LIDAR Measurements of Apple Orchards","volume":"82","author":"Walklate","year":"2002","journal-title":"Biosyst. Eng."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"108","DOI":"10.1016\/j.compag.2015.05.014","article-title":"Real time canopy density estimation using ultrasonic envelope signals in the orchard and vineyard","volume":"115","author":"Palleja","year":"2015","journal-title":"Comput. Electron. Agric."},{"key":"ref_27","unstructured":"Yang, Z.P., and Yan, X.L. (2003). Experimental Optimization Technique, Northweat A&F University Press. [1st ed.]. (In Chinese)."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"208","DOI":"10.4028\/www.scientific.net\/AMR.422.208","article-title":"Nozzle flow model of high pressure variable-rate spraying based on PWM technology","volume":"422","author":"Zhai","year":"2011","journal-title":"Adv. Mater. Res."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/1\/31\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T19:29:16Z","timestamp":1760210956000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/1\/31"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2016,12,24]]},"references-count":28,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2017,1]]}},"alternative-id":["s17010031"],"URL":"https:\/\/doi.org\/10.3390\/s17010031","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2016,12,24]]}}}