{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T04:25:25Z","timestamp":1760243125903,"version":"build-2065373602"},"reference-count":22,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2015,7,28]],"date-time":"2015-07-28T00:00:00Z","timestamp":1438041600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This paper demonstrates an automated computer vision system for outdoor tree crop enumeration in a seedling nursery. The complete system incorporates both hardware components (including an embedded microcontroller, an odometry encoder, and an uncalibrated digital color camera) and software algorithms (including microcontroller algorithms and the proposed algorithm for tree crop enumeration) required to obtain robust performance in a natural outdoor environment. The enumeration system uses a three-step image analysis process based upon: (1) an orthographic plant projection method integrating a perspective transform with automatic parameter estimation; (2) a plant counting method based on projection histograms; and (3) a double-counting avoidance method based on a homography transform. Experimental results demonstrate the ability to count large numbers of plants automatically with no human effort. Results show that, for tree seedlings having a height up to 40 cm and a within-row tree spacing of approximately 10 cm, the algorithms successfully estimated the number of plants with an average accuracy of 95.2% for trees within a single image and 98% for counting of the whole plant population in a large sequence of images.<\/jats:p>","DOI":"10.3390\/s150818427","type":"journal-article","created":{"date-parts":[[2015,7,28]],"date-time":"2015-07-28T10:14:12Z","timestamp":1438078452000},"page":"18427-18442","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Automated Mobile System for Accurate Outdoor Tree Crop Enumeration Using an Uncalibrated Camera"],"prefix":"10.3390","volume":"15","author":[{"given":"Thuy","family":"Nguyen","sequence":"first","affiliation":[{"name":"Department of Computer Science, University of California, Davis, CA 95616, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"David","family":"Slaughter","sequence":"additional","affiliation":[{"name":"Department of Biological and Agricultural Engineering, University of California, Davis,  CA 95616, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bradley","family":"Hanson","sequence":"additional","affiliation":[{"name":"Department of Plant Sciences, University of California, Davis, CA 95616, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Andrew","family":"Barber","sequence":"additional","affiliation":[{"name":"Department of Biological and Agricultural Engineering, University of California, Davis,  CA 95616, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Amy","family":"Freitas","sequence":"additional","affiliation":[{"name":"Department of Biological and Agricultural Engineering, University of California, Davis,  CA 95616, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Daniel","family":"Robles","sequence":"additional","affiliation":[{"name":"Department of Biological and Agricultural Engineering, University of California, Davis,  CA 95616, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Erin","family":"Whelan","sequence":"additional","affiliation":[{"name":"Department of Biological and Agricultural Engineering, University of California, Davis,  CA 95616, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2015,7,28]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"12132","DOI":"10.3390\/s130912132","article-title":"Sensors in agriculture and forestry","volume":"13","author":"Pajares","year":"2013","journal-title":"Sensors"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"4014","DOI":"10.3390\/s140304014","article-title":"Integrating sensory\/actuation systems in agricultural vehicles","volume":"14","author":"Emmi","year":"2014","journal-title":"Sensors"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"23885","DOI":"10.3390\/s141223885","article-title":"Multisensory system for fruit harvesting robots. 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Proceedings of the International Conference on Digital Manufacturing and Automation, Zhangjiajie, China.","DOI":"10.1109\/ICDMA.2011.106"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"10783","DOI":"10.3390\/s140610783","article-title":"Active optical sensors for tree stem detection and classification in nurseries","volume":"14","author":"Garrido","year":"2014","journal-title":"Sensors"},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Bazi, Y., Al-Sharari, H., and Melgani, F. (2009, January 12\u201317). An automatic method for counting olive trees in very high spatial remote sensing images. Proceedings of the IEEE International Geoscience and Remote Sensing Symposium, Cape Town, South Africa.","DOI":"10.1109\/IGARSS.2009.5418019"},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Bazi, Y., Malek, S., Alajlan, N., and AlHichri, H. (2014, January 13\u201318). An automatic approach for palm tree counting in UAV images. Proceedings of the IEEE International Geoscience and Remote Sensing Symposium, Quebec, QC, Canada.","DOI":"10.1109\/IGARSS.2014.6946478"},{"key":"ref_10","first-page":"151","article-title":"A novel image processing technique for counting the number of trees in a satellite image","volume":"1","author":"Kumar","year":"2012","journal-title":"Eur. J. Appl. Eng. Sci. Res."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"346","DOI":"10.1016\/j.cviu.2007.09.014","article-title":"SURF: Speeded up Robust Features","volume":"110","author":"Bay","year":"2008","journal-title":"Comput. Vis. Image Underst."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"2227","DOI":"10.1109\/TPAMI.2014.2321376","article-title":"Scalable nearest neighbor algorithms for high dimensional data","volume":"36","author":"Muja","year":"2014","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"7095","DOI":"10.3390\/s110707095","article-title":"Mapping wide row crops with video sequences acquired from a tractor moving at treatment speed","volume":"11","author":"Ribeiro","year":"2011","journal-title":"Sensors"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1109\/TVT.2010.2096832","article-title":"Compensating background for noise due to camera vibration in uncalibrated-camera-based vehicle speed measurement systems","volume":"60","author":"Nguyen","year":"2011","journal-title":"IEEE Trans. Veh. Technol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"6480","DOI":"10.3390\/s110606480","article-title":"An image segmentation based on a genetic algorithm for determining soil coverage by crop residues","volume":"11","author":"Ribeiro","year":"2011","journal-title":"Sensors"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"12405","DOI":"10.3390\/s120912405","article-title":"Towards autonomous agriculture: Automatic ground detection using trinocular stereovision","volume":"12","author":"Reina","year":"2012","journal-title":"Sensors"},{"key":"ref_17","first-page":"1761","article-title":"Outdoor field machine vision identification of tomato seedlings for automated weed control","volume":"40","author":"Tian","year":"1997","journal-title":"Trans. ASABE"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Ta, D.-N., Chen, W.C., Gelfand, N., and Pulli, K. (2009, January 20\u201325). SURFTrac: Efficient tracking and continuous object recognition using local feature descriptors. Proceedings of the IEEE International Conference on Computer Vision Pattern Recognition, Miami, FL, USA.","DOI":"10.1109\/CVPR.2009.5206831"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Juan, L., and Gwun, O. (2010, January 7\u201310). SURF applied in panorama image stitching. Proceedings of the International Conference on Image Processing Theory Tools and Applications, Paris, France.","DOI":"10.1109\/IPTA.2010.5586723"},{"key":"ref_20","unstructured":"Segundo, M.P., Gomes, L., Bellon, O.R.P., and Silva, L. (October, January 30). Automating 3D reconstruction pipeline by SURF-based alignment. Proceedings of the IEEE International Conference on Image Processing, Orlando, FL, USA."},{"key":"ref_21","first-page":"1423","article-title":"Scaling-translation parameter estimation using Genetic Hough Transform for background compensation","volume":"5","author":"Nguyen","year":"2011","journal-title":"KSII Trans. Internet Inf. Syst."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"e109809","DOI":"10.1371\/journal.pone.0109809","article-title":"A novel method of object detection from a moving camera based on image matching and frame coupling","volume":"9","author":"Chen","year":"2014","journal-title":"PLoS ONE"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/15\/8\/18427\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T20:49:51Z","timestamp":1760215791000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/15\/8\/18427"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2015,7,28]]},"references-count":22,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2015,8]]}},"alternative-id":["s150818427"],"URL":"https:\/\/doi.org\/10.3390\/s150818427","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2015,7,28]]}}}